| 1. |
- Forssén, Jens, 1968, et al.
(author)
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Thick barrier noise-reduction in the presence of atmospheric turbulence: Measurements and numerical modelling
- 2002
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 63:2, s. 173-187
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Journal article (peer-reviewed)abstract
- Atmospheric turbulence causes scattering of sound, which can reduce the performance of sound barriers. This is an important inclusion in prediction models to obtain a correct picture of the sound reduction at higher frequencies. Here a prediction method is applied that uses the strengths of the wind and temperature turbulence to estimate the scattered power into the shadow zone of a barrier. The predictions are compared to full-scale measurements on a thick barrier, where both acoustic and meteorological data were recorded simultaneously under both calm and windy conditions. Comparison between the measurements and the predictions indicate that the method gives reasonably accurate results for mid to high frequencies and a slight overestimation at very high frequencies.
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| 2. |
- Horoshenkov, K. V., et al.
(author)
-
The sound speed and attenuation in loose and consolidated granular formulations of high alumina cements
- 2003
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 64:2, s. 197-212
-
Journal article (peer-reviewed)abstract
- Clinkers of high alumina cements are separated into three granular formulations with particle sizes in the range 0.6-0.71 mm, 0.71-1.18 mm and greater than 1.18 mm. These are used to manufacture consolidated samples of porous concrete in an autoclave. The acoustic and microscopic properties of loose and consolidated porous samples of concrete are investigated using both experimental methods and mathematical modelling. Values of porosity, flow resistivity, tortuosity and parameters of the pore size distribution are determined and used to predict closely the sound speed, acoustic attenuation and normal incidence absorption coefficient of these materials. It is shown that high alumina cements do not require additional binders for consolidation and that the structural bonds in these cements are developed quickly between individual clinkers in the presence of water. The hydration product build-up during the consolidation process is insignificant which ensures good acoustic performance of the consolidated samples resulting from a sufficient proportion of the open pores. The value of porosity in the consolidated samples was found to be around 40%, which is close to that measured in some commercial acoustic absorbers. This work provides a foundation for the development of acoustically efficient and structurally robust materials, which can be integrated in environmentally sustainable concrete and masonry structures. © 2002 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Johansson, Carin
(author)
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Design and evaluation of an impact noise laboratory
- 1994
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 42:1, s. 75-84
-
Journal article (peer-reviewed)abstract
- An acoustic laboratory has been constructed in order to measure sound transmission through floors. It has been erected inside an existing building. Apart from the costs being considerably less than if a new building had been constructed, this has meant that several other advantages have been obtained. The design and location of the laboratory have been partially governed by activities already existing in the building. This article presents the construction from the point of view of building technique and of acoustics. In an effort to eliminate flank transmission in the frequency range 100–3150 Hz the construction has been dimensioned with vibration dampers having a natural frequency fo = 10 Hz. For the same reason and in order to increase the sound insulation the walls and ceiling have been lined with radiation reducing material. Comparative calculations and measurements have been carried out which show how the results have been affected by this procedure. The radiated effect from the various surfaces is shown in the form of graphs. The ratios of the receiving room dimensions are chosen so that the natural frequencies in the low-frequency region 100, 125 and 160 Hz are spaced fairly uniformly Despite the economic limitations and a limited amount of space the laboratory meets the requirement set by the International Standards ISO 140 with a good margin.
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| 4. |
- Johansson, Carin, et al.
(author)
-
Development of a lightweight wooden joist floor with high impact noise insulation
- 1994
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:1, s. 67-79
-
Journal article (peer-reviewed)abstract
- This article describes the results of a project for the development of a lightweight wooden joist floor. The work has been carried out by the optimization of each of the variables which are important for sound insulation and has resulted in the construction of a framing of joists which has good impact sound insulation, small dimensions, can be constructed in a simple way at low cost and can be assembled in an easy and safe way. Forty-five different constructions and combinations were tested in the laboratory. The optimal construction was finally tested in several blocks of flats. In order for the construction to meet the Swedish Building Standards for sound insulation, the impact noise index Ii must not exceed 63 dB. The final construction had an index Ii of 52 dB in the laboratory and 53–58 dB in the field, and was thus approximately 10 dB better that the standard limit for impact noise between adjoining flats. The total weight of the construction is only 60 kg/m2 and the total thickness is 342 mm. Furthermore the framing of joists is economical and practical to manufacture in factories, is easy to transport without deformation and is easy to install in the building on the site.
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| 5. |
- Johansson, Carin
(author)
-
Low-frequency impact sound insulation of a light weight wooden joist floor
- 1995
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 44:2, s. 133-147
-
Journal article (peer-reviewed)abstract
- This article describes the results of a project for the development of a lightweight wooden joist floor. The project concerns the further development of an earlier joist construction, in which very good laboratory and field results were obtained in the frequency range 100–3150 Hz. The work was carried out to investigate how impact sound at frequencies under 100 Hz is affected if the construction is made more rigid by various means. Attention was concentrated on the effect of increasing the rigidity of joists and boards. The report cover laboratory experiments as well as measurements in the field.
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| 6. |
- Johansson, Örjan, et al.
(author)
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Source characterization of the lower front-end of a diesel engine
- 1996
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 49:4, s. 383-404
-
Journal article (peer-reviewed)abstract
- The lower front end of a diesel engine is a major noise source. Describing the source mechanisms of this area is problematic as it consists of a rotating torsional vibration damper in front of the timing transmission cover and the oil sump. This experimental study focuses on the acoustic interaction phenomena between the damper and the structure behind it. To describe the source mechanisms a test series of different modifications by conventional lead wrapping technique is performed. The vibration behaviour of each substructure is determined by operational deflection shape measurements and the source strength for each modification is determined by near-field sound intensity measurements. The results show the contributions from different substructures and describes the interference effects due to coherent radiation. It is concluded that the radiation is dominated by the timing transmission cover structure behind the damper. At some frequencies though, the torsional vibration damper in combination with the timing transmission cover behind it, causes the high radiation. This effect is mainly due
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| 7. |
- Ljunggren, Fredrik, et al.
(author)
-
Development of a new damper to reduce resonant vibrations in lightweight steel joist floors
- 2002
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 63:11, s. 1267-1280
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Journal article (peer-reviewed)abstract
- Floor vibrations annoying to humans often occur in lightweight constructions. A number of methods to solve the problem of resonant vibrations are reported in the literature. Tuned mass damper, semi-active tuned vibration absorber and active control system are all examples of existing methods. A new method has been tested in laboratory environment on a prefabricated floor containing a resilient ceiling with a size up to 6.8×4.8 m2. The method takes advantage of small pieces of visco-elastic material connected between the ceiling joists and the primary beams. A finite element model is used to calculate the correct amount of visco-elastic material. The new damper is especially effective in damping mode shapes where the ceiling oscillates out of phase relative to the floor but shows improvements for other mode shapes as well.
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| 8. |
- Sandberg, Ulf, 1946-
(author)
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Road traffic noise : The influence of the road surface and its characterization
- 1987
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In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 21:2, s. 97-118
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Journal article (peer-reviewed)abstract
- Unacceptable errors in the prediction of traffic noise occur in some cases when the road surface is largely different from that on which the prediction model is based. The reason is that tyre/road noise has appeared to be the dominating component of the noise from free-flowing traffic and that this noise is to a substantial extent dependent on the road surface.The mechanisms for tyre/road noise generation and its relation to road characteristics are described. Relevant road surface characterization methods are suggested. The major method is the measurement of the road texture profile and subsequent spectral analysis of the profile curve. Supplementary methods concern the measurement of acoustical and mechanical impedances. It is concluded that the road surface effect on traffic noise is extremely complicated and that it is very difficult to generalize any simple relations.For free-flowing traffic it is shown that the tested road surface types and conditions may influence the traffic noise by up to 11 dB(A). This calls for a correction term for the road surface in the prediction models. Despite the complicated relations, it appears feasible—within stringent limitations—to use a table where the correction term is a variable of vehicle type, vehicle speed as well as road surface type and condition.
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| 9. |
- Shi, Wanqing, et al.
(author)
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An investigation of the characteristics of impact sound sources for impact sound insulation measurement
- 1997
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 51:1, s. 85-108
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Journal article (peer-reviewed)abstract
- At the assessment of the impact sound insulation of a construction, a standard tapping machine is used as sound source. However, the current standard tapping machine has been criticised especially for measurement of wooden joist floors since the sounds generated by a tapping machine differ from those generated by actual footfall. This study has investigated the waveform and frequency spectra of human footfall (walking, running and jumping), of sand balls, sand bags and dropped tires, and of the standard tapping machine. It is shown that the frequency spectra differ between the standard tapping machine and actual footfall, especially at low frequencies. Results from other excitation sources such as a sand ball falling from a certain height showed concordance with actual footfall. This means that a sand ball drop as an impact source provides a better representation of actual human footfall than the standard tapping machine.
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| 10. |
- Shi, Wanqing, et al.
(author)
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Assessment of the sound insulation of a wood joist construction due to different types of impact sources
- 1996
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 48:3, s. 195-203
-
Journal article (peer-reviewed)abstract
- The ISO standard tapping machine was specified as an impact source to assess the sound insulation of floors. The problem is that the noise spectrum produced by the tapping machine does not give similar spectra to that produced by an actual footfall. There are not enough low frequency components in the noise spectrum generated by the tapping machine and it does not, therefore, accurately reflect low frequency noise from the construction being measured. This study presents the impact sound power radiation from a wooden joist construction while applying different impact sources, actual footfall and the standard tapping machine. The sound power radiation obtained from the construction when the tapping machine is applied contains large discrepancies when compared with measurements obtained from an actual footfall at the lower frequency. Comparison of the sound power radiation from the wood joist construction generated by different impact sources showed very good agreement between an actual footfall and a sand ball falling from a certain height. This means that the use of the sand ball drop is a better method of assessing the low frequency impact sound insulation of a construction than using the standard tapping machine.
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| 11. |
- Ågren, Anders, et al.
(author)
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Experimental study of repeatability errors in 3D sound intensity measurements in narrow frequency bands
- 1994
-
In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:2, s. 95-111
-
Journal article (peer-reviewed)abstract
- When investigating the 2D or 3D intensity of complex ‘real life’ noise sources, rather than the intensity normal to a surface, to obtain more detailed information about the radiated sound field great care has to be taken both in measuring and in interpreting the results. In this study it is shown that in measurements of 3D intensity for fixed points and in narrow frequency bands, large errors can be expected for a well-defined simple source if the positioning is imprecise and for a complex source even if the positioning device and the probe are of highest quality. Comparisons have been made between a two-microphone and a six-microphone probe, hand-held and robot-controlled. The comparisons show that, except for the case of an ideal measurement with a simple source and a high-precision robot, significant errors can be expected for all the tested measurement cases. The measurements also show that the positioning of the microphone is of major importance for the repeatability accuracy. The accuracy obtained with a 3D-probe is notably better than with a 1D-probe. The errors when measuring the complex source with a robot-controlled 3D-probe, however, are still so high, especially for the non-dominant directions, that interpretations have to be made with great care. Under non-ideal measurement conditions, the errors are found to be exponentially dependent upon the sound field pressure/intensity relationship (the pI-index).
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| 12. |
- Ågren, Anders
(author)
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The design and evaluation of a semi-anechoic engine test room
- 1992
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In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 37:2, s. 151-161
-
Journal article (peer-reviewed)abstract
- A low-cost hemi-anechoic laboratory for study of diesel engine emissions has been constructed. The laboratory has been equipped for research in acoustics as well as on exhaust emissions. The facilities for acoustic research are described. A low-budget wall absorber with durable, inexpensive and easily exchangeable wedges has been designed. Various ways of evaluating the acoustic properties of hemi-anechoic rooms are investigated. Finally, measurements are presented that show sound level decay with distance from a source and the standard deviation for sound level when the source and microphone are rotated in a so-called carousel measurement. For sound level decay measurements a special extremely low loudspeaker must be used to avoid interfering floor reflections. Carousel measurements give good results even for a standard loudspeaker. Our carousel measurements show that the absorbers are as appropriate as other more expensive absorbers for measurements up to 2 m from a sound source.
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| 13. |
- Alberdi-Muniain, Ane, et al.
(author)
-
Indirect energy flow measurement in magneto-sensitive vibration isolator systems
- 2013
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 74:4, s. 575-584
-
Journal article (other academic/artistic)abstract
- The indirect energy flow measurement method is extended to cover highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber isolators applied in a real vibration isolation system. Energy flow is an effective measure of vibration isolation while being a single quantity that considers both force and velocity. The use of the indirect technique is of interest while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The vibration isolation system is composed of four magneto-sensitive rubber isolators that are inserted under a vibrating source consisting of a solid aluminium mass excited by an electro-dynamic shaker. Magneto-sensitive rubber isolators are more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field, thus resulting in more effective vibration isolation. Various approximations regarding the indirect technique are investigated, concluding that average stiffness of magneto-sensitive isolators can be used and auto-spectrum of the foundation velocity ignored. In addition, various error analyses are performed. Finally, the indirect measurement of the energy flow is validated by direct measurements, showing very good agreement.
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| 14. |
- Baro, Simone, et al.
(author)
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Modelling of a lined tyre for predicting cavity noise mitigation
- 2019
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In: Applied Acoustics. - : ELSEVIER SCI LTD. - 0003-682X .- 1872-910X. ; 155, s. 391-400
-
Journal article (peer-reviewed)abstract
- Tyre cavity resonance can significantly affect vehicle interior noise at frequencies around 200 Hz. The insertion of a sound absorbing liner inside the tyre is known to be an efficient countermeasure, in fact nowadays tyre manufacturers are already producing tyres implementing this kind of solution. The present work, through analytical and numerical models, supported by material testing, provides a methodology for predicting the dag performance of a lined tyre, taking into account tyre/lining geometry and sound absorbing material properties. The results reported in the paper show that for fixed material characteristics, the attenuation of the cavity resonance is mostly influenced by the volume of the lining treatment. Moreover, the numerical model developed for discontinuous treatments, suggests that for fixed volume and material properties, the cavity resonance attenuation can be increased by choosing a proper layout. Elsevier Ltd. All rights reserved.
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| 15. |
- Bosser, Lennart, et al.
(author)
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Target echo calculations using the OpenGL graphics pipeline
- 2021
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In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 181
-
Journal article (peer-reviewed)abstract
- This paper presents a novel approach to using modern graphics card capabilities for predicting the hydroacoustic target echo strength of an object. The key feature of this method is to inject code in the fragment shader stage of the OpenGL graphics pipeline, in effect transforming the optics reflection problem of computer graphics to an acoustic reflection problem. This is exemplified with the simple situation of an acoustically hard body and the monostatic detection case. Numerical accuracy is compared with Kirchhoff theory for simple bodies. Some suggestions for further work are proposed. (C) 2021 Elsevier Ltd. All rights reserved.
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| 16. |
- Braat-Eggen, Ella, et al.
(author)
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Auditory distraction in open-plan study environments : Effects of background speech and reverberation time on a collaboration task
- 2019
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 154, s. 148-160
-
Journal article (peer-reviewed)abstract
- Previous research has shown that semantic-based tasks are negatively influenced by semantic aspects in background speech. Collaboration is an important task in open-plan study environments and is a semantic task which might be disrupted by background speech. Therefore, the aim of this study was to analyze the influence of irrelevant background speech on student-collaboration. Participants worked in pairs to solve spot-the-difference puzzles, by using the 'DiapixUK' collaboration task, while they were exposed to different background sound scenarios. The composed sound scenarios varied in semantic content (mother tongue and foreign language background speech)and reverberation time (short vs long), the latter affecting speech intelligibility. Although a longer reverberation time decreases the intelligibility of background speech and a foreign language decreases meaningfulness of speech, no significant changes in performance were found. On the other hand, the data show an increased perceived disturbance for a longer reverberation time, which we interpret as an increased difficulty of interpersonal communication in the collaboration task due to the increased level of the background speech. The quiet reference condition was the most preferred sound condition which is in line with both the effect of a low background sound level and the absence of semantic interference.
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| 17. |
- Cameron, Christopher John, et al.
(author)
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Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz
- 2010
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 71:8, s. 708-721
-
Journal article (peer-reviewed)abstract
- The work within this paper focuses on the application and validation of numerical methods for predicting the acoustic and structural NVH behaviour of trimmed body components in an automotive context. In particular, the level of modelling refinement and accuracy necessary to establish a reliable finite element analysis model for comparative purposes in the development of alternative designs is investigated. Specifically, the roof structure of a passenger car was investigated from various performance aspects, using both structural and acoustic excitation. The roof was initially tested in situ, with and without interior lining, to provide a reference for subsequent component tests. It was then detached from the car, mounted in a stiff frame and tested in a transmission window using both acoustic and structural excitation. A finite element model of the detached component was developed using shell and solid elements for the structure and solid elements for the interior lining. Predictions were carried out to evaluate the STL as well as the vibrational frequency response due to a force applied to the structure. Special attention was given to the modelling of the headliner as well as the air gap separating the headliner from the outer sheet metal. A sensitivity study of various headliner properties was performed in addition to a comparison between solutions calculated using standard Nastran elements and augmented poro-elastic elements via the software package CDH/EXEL. The main objective of the current work has been to establish a datum reference for alternative designs. From this aspect, the validation of the numerical modelling methodology, in particular the level of detail and accuracy used, was a crucial step. It was found that the predictions agreed very well with the measured data. As an additional, very interesting result, it was also found that the in situ testing correlated well with the transmission suite testing.
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| 18. |
- Conrady, Kristina, et al.
(author)
-
Amplitude modulation of wind turbine sound in cold climates
- 2020
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 158
-
Journal article (peer-reviewed)abstract
- Amplitude modulation is assumed to be a major annoyance factor of wind turbine sound. However, studies on the generation of amplitude modulation and the impact of atmospheric conditions on amplitude modulation are limited, especially in cold climates. Long-term acoustic and meteorological measurements in the vicinity of a wind farm in northern Sweden show a dependence of the occurrence of amplitude modulation on wind direction and atmospheric stability. The occurrence of amplitude modulation is highest for crosswinds from southwest, compared with the other wind directions. Moreover, the occurrence of amplitude modulation is clearly linked to atmospheric stability and highest for very stable conditions. The impact of atmospheric stability is supported by analyses of wind shear, the wind speed gradient close to the surface and the bulk Richardson number. Amplitude modulation is more likely during winter than during summer and more likely during night and early morning than during noon and early afternoon.
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| 19. |
- Dickson, Crispin, et al.
(author)
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Continuous judgment by category-ratio scaling of aircraft noise
- 2014
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In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 84, s. 3-8
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Journal article (peer-reviewed)abstract
- A continuous judgment by category-ratio (CJCR) scaling method was used to evaluate the instantaneous annoyance of original and modified aircraft sounds. The result from the proposed method resulted in a temporal stream of annoyance levels for the whole flyover sequence that could be further analyzed. The test subjects were continuously rating their instantaneous annoyance on a Borg CR 100 scale (R) during the playback of 10 flyover sequences. Using a category-ratio (CR) scale instead of a category (C) scale, mathematical operations such as calculations of average were enabled but gave also advantages in terms of higher resolution in the responses. The results showed differences in perception in the time segment where the sound had been modified. The temporal stream of annoyance was also converted into overall judgments of the sounds, these estimations showed consistency with previous results obtained using the semantic differential and paired comparison method.
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| 20. |
- Estévez Mauriz, Laura, 1982, et al.
(author)
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Dynamic traffic noise assessment tool: A comparative study between a roundabout and a signalised intersection
- 2018
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 130, s. 71-86
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Journal article (peer-reviewed)abstract
- Considering traffic flow as a steady noise source is common practice when studying traffic alternatives and its impact on the sound environment. However, vehicle dynamics have a strong influence on both transport behaviour and noise emission. One of the most relevant elements of traffic design is the intersection, where replacement of crossing intersections with roundabouts is common. In order to understand the features of these two traffic configurations, microscopic approaches are needed, making it possible to study time-pattern fluctuations relevant for the urban sound environment perception. A model based on individual-vehicle characteristics as function of time is developed and implemented in a real case study at a development stage. The model incorporates state-of-art microscopic traffic simulation software combined with the recent noise emission model, CNOSSOS-EU, applied through an in-house developed dynamic traffic noise tool, including both internal combustion engine and all-electric vehicles at different traffic flows. The tool is described in general terms incorporating the randomisation of source power. The propagation considers a flat-city configuration up to 100 m range. The tool enables study of different statistical indicators, including descriptors of probability density functions, calm periods through the novel indicator Centre of Mass Time (CMT) and noise events. The outcomes are presented through graphs and maps explaining traffic disruptions, acceleration effects, vehicle configurations and flows, source strengths, contribution and difference maps. Among the results, it is shown that, for the signalised crossing, the acceleration of the simulated traffic has a large effect on the source strength. It is however also shown that, for an unbalanced roundabout intersection leading to congestions, it can become noisier than the signalised crossing. It is furthermore shown that, when reducing the traffic flow, the two intersection types behave more similarly; however the roundabout having the best performance for the majority of the studied analysis. Further results are shown, e.g. for removing heavy vehicles, removing also medium heavy vehicles and assuming only all-electric light vehicles, including analysis from using various indicators. A discussion about the presented tool, the current results and ideas for future work concludes the paper. The present paper goes along a series of studies with the overall intention to provide a more solid basis for justifying decisions in traffic planning regarding the outdoor sound environment.
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| 21. |
- Feng, Leping, et al.
(author)
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Engineering methods to predict noise levels at reference points with known source properties
- 2015
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In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 96, s. 68-74
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Journal article (peer-reviewed)abstract
- Two engineering methods are proposed to predict the sound pressure levels at a given point when the sound power level of a noise source is known and the transfer function between the source and the reference point can be obtained. The first method is applicable when the source is surrounded by many reflectors, or inside a box-like structure. A single monopole with average transfer function is suggested for this situation. For a source with a strong directivity placed in an essentially free space, the "box-source" method is recommended to take into account of the source directivity. The total sound power is in this case divided into five independent noise sources which are obtained via ordinary sound power measurement methods. Experimental verifications are made for several cases in laboratory. Satisfactory results are obtained for both methods.
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| 22. |
- Feng, Leping
(author)
-
Modified impedance tube measurements and energy dissipation inside absorptive materials
- 2013
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 71:12, s. 1480-1485
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Journal article (peer-reviewed)abstract
- Impedance tube is an important tool to measure acoustic properties of a material, for which two methods have been standardized. The methods for a "modified" impedance tube have been developed recently to measure material properties in the condition of an anechoic termination. Instead of commonly used two-load or two-source methods, a method with direct and inverted configuration in cooperation with the single-microphone method is suggested in this paper. With the help of transfer matrix method, combined effect of several materials placed in series can be predicted from individual properties. A simple recurrence formula is obtained to relate the acoustic properties of a multilayer structure with the reflection and transmission coefficients of each layer. Very good agreements are obtained between the prediction and the direct measurements. Energy dissipations inside porous materials for different situations are studied and compared.
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| 23. |
- Forssén, Jens, 1968, et al.
(author)
-
Auralization model for the perceptual evaluation of tyre–road noise
- 2018
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 132, s. 232-242
-
Journal article (peer-reviewed)abstract
- Due to improvements in combustion-engines and use of electric-engines for cars, tyre noise has become the prominent noise source also at lower speeds. Models exist that simulate the noise produced by a rolling tyre, as do models that auralize different traffic situations from basic data. In this paper, a novel auralization method is introduced, with the purpose to enable synthesis of useful car pass-by sound signals for various situations. The method is based on an established model for tyre noise levels (SPERoN) that is combined with a validated auralization tool (LISTEN). In the LISTEN approach, source signals for tyre–road interaction and propulsion are produced from data based on recorded pass-by sounds. In the combined model, the tyre–road interaction data is shaped by the spectra estimated in SPERoN and synthesized back into a pass-by signal. The combined model is made to agree spectrally with measurements for a receiver at 7.5 m distance. Psychoacoustic judgments were used to compare the modelled signals with recorded signals, and the pass-by sounds for a given listener position showed promising quality and accuracy with respect to perceived pleasantness.
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| 24. |
- Forssén, Jens, 1968, et al.
(author)
-
Effects of urban morphology on traffic noise: A parameter study including indirect noise exposure and estimated health impact
- 2022
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 186
-
Journal article (peer-reviewed)abstract
- Noise exposure has been calculated and analysed for 31 different urban morphologies in an urban setting. For five of the urban morphologies also vegetation surfaces on facades and roofs were studied. Facade exposures were analysed for both smaller (single-sided) flats and larger (floor-through) flats, considering the direct exposure from the roads as well as the indirect exposure at noise-shielded positions like inner yards. Also, grid map area exposures at ground level were calculated and analysed for both sidewalk and yard areas. The facade exposure levels, using indicators Lden and Lnight, were used to estimate annoyance and sleep disturbance as well as disease burden in terms of DALY (Disability-Adjusted Life Years) per person. In all urban morphology cases, single-sided flats showed overall better performance (i.e. lower DALY) than larger, floor-through flats; however, the inclusion of a bonus for additional facade elements having a lower noise exposure gave the large flats a similar or better predicted overall performance compared with the small flats. Among the building types studied, for small flats and constant building density, the use of perimeter blocks with closed inner yards, slightly open yards and U-shaped buildings showed results of relatively better overall performance compared with I-shaped, L-shaped and point buildings. When the yards grow in size, the performance of closed inner yards dropped. As general trends, perimeter blocks were shown to perform better than morphologies with less enclosed yards and densification with constant traffic flow was shown to result in improved performance. However, building types with slightly open yards may provide an attractive compromise solution due to its relatively good noise shielding at the same time as enabling solutions to air pollution and corner-flat layouts. In addition, complementing the perimeter blocks with towers was shown to enable improvement. Furthermore, traffic concentration by locating all local traffic to a single road was shown to be beneficial, increasingly so by widening the road. Predicted effects of vegetation surfaces on facades and roofs showed significant overall improvement, where closed inner yards benefit from vegetated roofs. The area exposure results showed that when the building blocks are successively less enclosed the levels are reduced on the side-walks and increased in the yards. Also, the benefit of facade vegetation is shown for the area exposures. (C) 2021 The Author(s). Published by Elsevier Ltd.
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| 25. |
- Forssén, Jens, 1968, et al.
(author)
-
Modelling the interior sound field of a railway vehicle using statistical energy analysis
- 2012
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 73:4, s. 307-311
-
Journal article (peer-reviewed)abstract
- The sound field in train compartments, treated as a series of connected air cavities, is modelled using statistical energy analysis, SEA. For the case under study, with five cavities in series and the source in the second cavity, a closed-form solution is obtained. An adjusted SEA model is used to predict the rate of spatial decay within a cavity. The SEA model is validated using results from a ray tracing method and from scale model measurements. For the octave bands 500-4000 Hz, good agreement is shown between the results from measurements, the ray tracing and the SEA model, for the two saloons closest to the source cavity (a vestibule). The SEA model was shown to slightly underestimate the rate of spatial decay within a cavity. It is concluded that a reasonable cause is the additional diffusion due to the seating.
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| 26. |
- Forssén, Jens, 1968
(author)
-
Scintillating and decorrelating signals for different propagation paths in a random medium
- 2024
-
In: Applied Acoustics. - 0003-682X .- 1872-910X. ; 221
-
Journal article (peer-reviewed)abstract
- Randomness in the medium of propagation affects the signal received at a distance from a source resulting in amplitude and phase fluctuations as well as reduced coherence between different paths of propagation. A method is described and validated for incorporating such fluctuations and decorrelations in sound signals in a single approach. Here, simplified conditions are used of open space, with or without a single reflecting surface, assuming fluctuations as for plane waves in homogeneous and isotropic temperature turbulence. Validating results are shown for Gaussian and von Karman turbulence models and exemplifying sound clips are provided as supplementary material.
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| 27. |
- Frenne, Nicklas, et al.
(author)
-
Acoustic time histories from vibrating surfaces of a diesel engine
- 2006
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 67:3, s. 230-248
-
Journal article (peer-reviewed)abstract
- An experiment on a diesel engine provides for validation of a method that retrieves source strength spectra, source strength time histories and sound pressure time histories of the engine's complex partial sources. The method is based on empirical transfer function measurements and inverse matrix calculations briefly described in the article. Different simplifying source models were selected by comparison of calculated and measured auto spectra. The results show: (1) indication of time efficient measurements of source strength spectra, (2) the importance of correct source models in the case of separated source strength time histories, and (3) spectra of separated sound pressure time histories. Listening tests reported that it is possible to detect well differentiated sounds of the partial sources as a result of the method.
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| 28. |
- Färm, Anna, 1984-, et al.
(author)
-
Absorption of sound at a surface exposed to flow and temperature gradients
- 2016
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 110, s. 33-42
-
Journal article (other academic/artistic)abstract
- In noise abatement using porous or fibrous materials, accurate determination of the surface impedance representing the absorber is decisive for simulation quality. The presence of grazing flow and non-homogeneous ambient temperature influence the reaction of the absorber and may suitably be included in a modified “effective” surface impedance. In this paper, this approach is applied to a generic case representative for the engine bay of a heavy truck, where porous shields suppress the radiated noise, e.g. during a pass-by noise test. The change in the absorption is determined numerically by solving the wave propagation through a layer of varying temperature and flow adjacent to the impedance surface for different angles of incidence. The study shows significant impact of both flow and temperature, especially for materials with low absorption. The diffuse field absorption coefficient is also derived and although the effect is less pronounced in this case, it is still important in lower frequencies and in the frequency range typical for IC engine noise. The proposed numerical method is shown to be accurate and efficient for determination of the effective impedance and moreover not limited to thin boundary layers.
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| 29. |
- Garnell, Emil, et al.
(author)
-
The use of the two-port method to characterize high-speed small fans
- 2019
-
In: Applied Acoustics. - : ELSEVIER SCI LTD. - 0003-682X .- 1872-910X. ; 146, s. 155-163
-
Journal article (peer-reviewed)abstract
- One way to obtain a complete characterization of a sound source in a duct is to measure two-port data, comprising of the source scattering matrix and the source cross-spectrum. The present paper discusses in detail the design and construction of a two-port rig to characterize high speed small fans. A new post-processing method is suggested for the source cross-spectrum data and is compared to an earlier published method. The new method is shown to behave better in highly reflective cases, but is more sensitive to flow noise. In some cases, the duct diameter is not equal to the diameter of the test object. An adaptor can then be used to match the diameters, but it will modify the two-port results. In the present paper a method to remove the adaptor influence on the measured scattering matrix and source vector is presented, and validated by measurements.
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| 30. |
- Hoffmann, Alice, 1983, et al.
(author)
-
Auralization of simulated tyre noise: Psychoacoustic validation of a combined model
- 2019
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 145, s. 220-227
-
Journal article (peer-reviewed)abstract
- Due to improvements on combustion-engines and electric-engines for cars, tyre noise has become the prominent noise source at low and medium speeds. Models exist that simulate the noise produced by a rolling tyre, as do models that auralize different traffic situations from a basic data set. In this paper, an established model for tyre noise (SPERoN) is combined with an auralization tool. The combined model can predict the spectrum of the sound at 7.5 m, as well as reproduce the sound for a given listener position. The auralization uses a methodology where recorded sounds are converted to source signals for engine and tyre/road-interaction. These can be shaped by the spectra estimated in SPERoN and synthesized back into a pass-by signal. Psychoacoustic judgements were used to compare the modelled signals with recorded signals. To see how well the modelled signals match the real recorded signals for perception, two listening-tests were performed. The simulated and recorded signals were rated by pleasantness, loudness, roughness and sharpness using semantic differentials. It was found that responses for simulated and recorded signals correlate for all cases, but rankings could not be reproduced exactly. The model can be further improved to be more applicable for listening tests.
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| 31. |
- Hornikx, Maarten, 1980, et al.
(author)
-
Modelling of sound propagation to three-dimensional urban courtyards using the extended fourier PSTD method
- 2011
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 72:9, s. 665-676
-
Journal article (peer-reviewed)abstract
- Noise from road traffic propagates to acoustically shielded areas as roadside courtyard by multiple reflection and diffraction paths in a complex three-dimensional (3D) environment. The computation of noise levels and assessment of candidate noise mitigation measures for these areas has up to now been based upon two-dimensional (2D) geometrical assumptions. Here, a recently developed efficient wave-based method, the extended Fourier pseudospectral time-domain (PSTD) method, is used to investigate the necessity of a 3D model. For frequencies up to 500 Hz and low traffic velocities of 30 km/h and 50 km/h, a road traffic noise configuration of an urban street canyon with or without cross streets and a closed roadside courtyard is compared to the 2D configuration as studied previously. It can be concluded that the contribution of distant sources is overpredicted by the 20 configuration. As noise mitigation measures, additional facade absorption, facade screens and roof screens have been studied. Results show that the 2D configuration underpredicts the effect of facade mitigation measures, by maximum 1.5 dB(A) for the absorption case and 4.4 dB(A) for the screens case. The effect of roof screens is overpredicted up to 1.7 dB(A). Given these deviations and the found deviations between the 3D configurations of street canyon with and without cross streets, the need for a 3D model can be concluded to be strongly configuration dependent. The 3D model is finally used to investigate the effect of a facade opening to the courtyard, which could lead to up to 10 dB(A) higher noise levels as compared to the noise propagating over the roof level and may prohibit the use of these courtyards as quiet areas. Absorption in the facade opening can significantly limit this negative effect.
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| 32. |
|
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| 33. |
- Hynninen, Antti, et al.
(author)
-
Determination of in-duct sound power beyond the plane wave range using wall-mounted microphones
- 2015
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 99, s. 24-30
-
Journal article (peer-reviewed)abstract
- When studying the acoustic wave propagation in a duct, the frequency range can be divided into the low frequency plane wave range and the high frequency range with non-plane waves. In the low frequency range, the wave propagation is one-dimensional and the governing equations are rather simple. The larger the duct, the lower the frequency limit of the non-plane waves. Therefore, also taking into account the three-dimensional acoustic wave propagation is important, especially when considering the duct systems used in large machines. In practice often a harsh environment and immobile structures restrict the use of standardized noise measuring methods. For instance to characterize the exhaust noise of medium speed internal combustion engines (IC-engines) in situ, the in-duct sound pressures are measured using wall-mounted microphones. Then the low frequency range source sound power can be estimated by wave decomposition ("two-microphone method"). Often a three-microphone array is used to cover a sufficiently large frequency range. One way to formulate the sound pressure and sound power relationship in the high frequency range is to weight the sound pressures at the duct wall in one-third octave bands. The aim of this study is to extend the classical plane wave formulation by determining these weighting factors, so that a three-microphone array also can be used beyond the plane wave range. The results from numerical approach are compared to experimental data.
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| 34. |
|
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| 35. |
- Jansson, Erik V.
(author)
-
Violin frequency response : bridge mobility and bridge feet distance
- 2004
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 65:12, s. 1197-1205
-
Journal article (peer-reviewed)abstract
- Good violins have a broad hill in the 2-3 kHz range of their frequency response. This hill has previously been attributed to the first in-plane resonance of the violin bridge. Experiments prove, however, that the hill is the result of two forces acting in opposite directions at the bridge feet. The experiments reported here show that the hill can be "tuned" by altering the distance between the bridge feet. It can be tuned both in terms of frequency and level but the properties of the violin cannot be neglected.
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| 36. |
- Jeon, Jin Yong, et al.
(author)
-
A cross-national comparison in assessment of urban park soundscapes in France, Korea, and Sweden through laboratory experiments
- 2018
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 133, s. 107-117
-
Journal article (peer-reviewed)abstract
- This study aims at examining the effect of socio-cultural context, including language, on soundscape assessments in urban parks. In total, 95 persons took part in three laboratory experiments, conducted in France (30 participants), Korea (30 participants) and Sweden (35 participants). Twenty-eight audio-visual excerpts from recordings conducted in five urban parks were used as stimuli. The participants evaluated soundscape quality using attribute scales provided in their own native languages. Principal Components Analysis produced two principal components of perceived affective quality, Pleasantness and Eventfulness. There were high levels of similarity in attributes associated with the Pleasantness among the three countries, whereas some differences were observed in the attributes related to Eventfulness. Two hierarchical cluster analyses were conducted based on perceived dominance of sound sources, and component scores of perceived affective quality. There were no significant differences in clustering results based on perceived dominance of sound sources among the different nationalities. In contrast, discrepancies were found in the clustering results based on perceived affective quality. In particular, perceptual responses to human sounds, birdsong, and water sounds, which are closely related to Eventfulness, were significantly different across the three cultural backgrounds. These findings provide empirical evidence of socio-cultural differences in soundscape assessment.
|
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| 37. |
- Johnsson, Roger, et al.
(author)
-
A new test track for automotive squeak and rattle (S&R) detection
- 2014
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 80, s. 79-85
-
Journal article (peer-reviewed)abstract
- The perceived quality of interior sounds is of increasing importance in the automotive industry since it is important for the customer perception of vehicle quality. Squeak and rattle (S&R) is a group of intermittent interior noise that reduce the sense of quality dramatically. To identify and solve S&R problems the car manufacturers do both simulations and tests in laboratory of complete vehicles as well as subsystems. As a complement, to laboratory testing and for verification, complete vehicle tests at proving grounds are done. In order to systematically test for vehicle S&R noise at proving grounds there is a need for a new type of test track that in a controlled and repetitive ways excite vehicles at different frequencies. This paper describes such a new test track, called the Frequency Sweep Test Track (FSTT). The test track is based on sweep excitation and improves the precision when detecting and solving S&R issues. Different design considerations such as sweep waveform, frequency range and sweep rate are discussed. The track design is evaluated using a quarter-car model including a tandem ellipsoid tyre model. In a case study a FSTT was built and the excitation of a car was measured. The track excited the expected frequency range and the track operated well in detecting a rattle in the dashboard of an executive production car and at which frequency the rattle occurred.
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| 38. |
- Keus van de Poll, Marijke, et al.
(author)
-
Disruption of writing by background speech: The role of speech transmission index
- 2014
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 81, s. 15-18
-
Journal article (peer-reviewed)abstract
- Speech transmission index (STI) is an objective measure of the acoustic properties of office environments and is used to specify norms for acceptable acoustic work conditions. Yet, the tasks used to evaluate the effects of varying STIs on work performance have often been focusing on memory (as memory of visually presented words) and reading tasks and may not give a complete view of the severity even of low STI values (i.e., when speech intelligibility is low). Against this background, we used a more typical office-work task in the present study. The participants were asked to write short essays (5 min per essay) in 5 different STI conditions (0.08; 0.23; 0.34; 0.50; and 0.71). Writing fluency dropped drastically and the number of pauses longer than 5 s increased at STI values above 0.23. This study shows that realistic work-related performance drops even at low STI values and has implications for how to evaluate acoustic conditions in school and office environments.
|
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| 39. |
- Kårekull, Oscar, et al.
(author)
-
Prediction model of flow duct constriction noise
- 2014
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 82, s. 45-52
-
Journal article (peer-reviewed)abstract
- The scaling law for aerodynamic dipole type of sound from constrictions in low speed flow ducts by Nelson and Morfey is revisited. A summary of earlier published results using this scaling law is presented together with some new data. Based on this, an effort to find a general scaling law for the sound power for components with both distinct and non-distinct flow separation points are made. Special care is taken to apply the same scaling to all data based on the pressure drop. Results from both rectangular and circular ducts, duct flow velocities from 2 to 120 m/s and sound power measurements made both in ducts and in reverberation chambers are presented. The computed sound power represents the downstream source output in a reflection free duct. In particular for the low frequency plane wave range strong reflections from e.g. openings can affect the sound power output. This is handled by reformulating the Nelson and Morfey model in the form of an active acoustic 2-port. The pressure loss information needed for the semi-empirical scaling law can be gained from CFD simulations. A method using Reynold Average Navier Stokes (RANS) simulations is presented, where the required mesh quality is evaluated and estimation of the dipole source strength via the use of the pressure drop is compared to using the turbulent kinetic energy.
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| 40. |
- Lemlikchi, Safia, et al.
(author)
-
Parametric estimation of overlapping echoes reflected from coated media
- 2021
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 178
-
Journal article (peer-reviewed)abstract
- In this work, a parametric modeling strategy was used to investigate ultrasonic signals reflecting from coated structures. The model parameter vector is defined by the combined model consisting of hard and soft modeling. The hard model describes the overlap with pure delays, reflection and transmission coefficients. The soft model copes with a more realistic case when all ultrasonic losses are included. The estimation procedure follows the maximum likelihood approach and uses the Levenberg–Marquardt algorithm for optimizing the objective function. The tested waveforms were reflected from thermally sprayed Diamalloy 4060 coatings deposited on 310SS substrate with increasing degree of overlapping echoes. Measurements were carried out in pulse-echo mode using a 15 MHz nominal frequency transducer. A good prediction of overlapping signals was achieved. Reverberating coating echoes were successfully separated and coating properties (time-of-flight (TOF), ultrasonic velocity and attenuation) were directly deduced. Results show the potential of the method to investigate overlapping ultrasonic signals reflecting from highly attenuating layers such as thermal sprayed coatings. It also shows the ability for the method to make a complete separation of the overlapping echoes, not only between the substrate and the coating echoes, but also between the reverberations in the coating itself that has been neglected for a long time. This allows an accurate characterization of the coating properties.
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| 41. |
- Lennström, David, et al.
(author)
-
Validation of the blocked force method for various boundary conditions for automotive source characterization
- 2016
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 102, s. 108-119
-
Journal article (peer-reviewed)abstract
- Vibro-acoustic source characterization is an essential task in vehicle development to enable prediction of receiver response. For structure-borne noise, the interface forces in multiple degrees of freedom due to internal loads are often quantified for root cause analyses in a single system assembly, as in transfer path analysis (TPA). However, for a reliable prognosis of the acoustic performance of a known component such as a motor or pump, a receiver-independent source characterization is required, and the method of acquiring blocked forces from in-situ measurements has been shown to be a preferred technique for such purposes. The benefits of the method are the characterization of the intrinsic properties of the source and the possibilities of measuring the component attached to receivers with varying dynamic properties.There is to date a limited number of validation cases where blocked forces from in-situ measurements are acquired for automotive source–receiver assemblies. In this study the blocked forces of a vacuum pump in nine degrees of freedom were determined when connected to a bracket whose boundary conditions were modified in order to achieve four assemblies with different source/receiver dynamic properties. The results show that the blocked forces are transferable, i.e. the receiver response in one assembly was predicted in a wide frequency range by combining source–receiver transfer functions of that assembly with blocked forces estimated in another assembly. Furthermore, an in-situ blocked force TPA was applied to a double-isolated complete vehicle source–receiver case of an electric rear axle drive with interior compartment sound pressure as target. The reconstructed magnetic tonal harmonics agreed with the measured target response in the frequency range 50–500 Hz, which further motivates the use of the blocked force principles for TPA and source requirements specifications.
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| 42. |
- Liguori, Consolatina, et al.
(author)
-
Estimation of the minimum measurement time interval in acoustic noise
- 2017
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 127, s. 126-132
-
Journal article (peer-reviewed)abstract
- The appropriate choice of the minimum measurement time interval is introduced for an accurate estimation of environmental noise indicators. The proposal is based on a bootstrap approach for the continuous estimation of measurement uncertainty in order to determine the statistical variability of the acquired sound pressure levels. Experimental results concerning the adoption of the proposed method regarding environmental noise from three different sources (road traffic, outdoor air conditioner fan motor and construction site) confirm the reliability of the proposal and its feasibility in evaluating the equivalent sound pressure level of an acoustic phenomenon using short-term indicators.
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| 43. |
- Lindberg, Eskil, 1979-, et al.
(author)
-
A vibro-acoustic reduced order model using undeformed coupling interface substructuring - Application to rubber bushing isolation in vehicle suspension systems
- 2014
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 78, s. 43-50
-
Journal article (peer-reviewed)abstract
- A vibro-acoustic reduced order model (ROM) based on a substructuring method using undeformed coupling interfaces (UCI) is proposed. The method may be used to reduce the order of a global problem, this by subdividing the global system to substructures interacting through UCI's. The local dynamic stiffness of each substructure may then be modelled with a, for that particular problem, best suited description. The feasibility of the method is demonstrated by a sensitivity analysis of the vibro-acoustic power isolation in a vehicle suspension system, comprising of a link arm connected to a vehicle car body through two rubber bushings. The link arm ROM is a component mode synthesis (CMS)-UCI, the rubber bushing model is a UCI-ROM derived from a 2D axisymmetric model using a frequency dependent visco-elastic material model. Finally the car body model is a frequency dependent UCI-ROM from a full car body finite element model. It is shown that the UCI-ROM approach efficiently can be used for parametric studies on a substructure level. The results suggest that the performed reorientation of the rubber bushings can alter, with orders of magnitude, the energy flow into the car.
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| 44. |
- Lindberg, Eskil, et al.
(author)
-
An experimental study of interior vehicle roughness noise from disc brake systems
- 2013
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 74:3, s. 396-406
-
Journal article (peer-reviewed)abstract
- An experimental study of the friction-induced noise generated by the disc brake system of a passenger car is presented. In particular, the brake noise usually referred to as wire brush or roughness noise is studied. This is, in terms of frequency spectral content a broadband phenomenon, resulting from the interaction of multiple asperities in the tribological contact. A new experimental method for measurements of disc brake roughness noise is proposed, and is used in a lab environment where the vehicle speed and the brake pressure are accurately controlled. The aim is to study the influence of vehicle speed and brake pressure on the roughness noise inside the vehicle. It is shown for the specific test case that the transmission from the source to the interior is a vibro-acoustic structure-borne phenomenon. Measurements show that there is a, as expected, strong correlation between increased interior noise and both increased vehicle speed and brake pressure.
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| 45. |
- Lindborg, PerMagnus, 1968-
(author)
-
A taxonomy of sound sources in restaurants
-
In: Applied Acoustics. - 0003-682X .- 1872-910X.
-
Journal article (peer-reviewed)abstract
- Restaurants are complex environments where all our senses are engaged. Physical and psychoacoustic factors have been shown to be associated with perceived environmental quality in restaurants. More or less designable sound sources such as background music, voices, and kitchen noises are believed to be important in relation to the overall perception of the soundscape. Previous research publications have suggested typologies and other structured descriptions of sound sources for some environmental contexts, such as urban parks and offices, but there is no detailed account that is relevant to restaurants. While existing classification schemes might be extendable, an empirical approach was taken in the present work. We collected on-site data in 40 restaurants (n = 393), including perceptual ratings, free-form annotations of characteristic sounds and whether they were liked or not, and free-form descriptive words for the environment as a whole. The annotations were subjected to analysis using a cladistic approach and yielded a multi-level taxonomy of perceived sound sources in restaurants. Ten different classification taxa were evaluated by comparing the respondents' Liking of sound sources, by categories defined in the taxonomy, and their Pleasantness rating of the environment as a whole. Correlation analysis revealed that a four-level clade was efficient and outperformed alternatives. Internal validation of the Pleasantness construct was made through separate ratings (n = 7) of on-site free-form descriptions of the environment. External validation was made with ratings from a separate listening experiment (n = 48). The two validations demonstrated that the four-level Sound Sources in Restaurants (SSR) clade had good construct validity and external robustness. Analysis of the data revealed two findings. Voice-related characteristic sounds including a ‘people’ specifier were more liked than those without such a specifier (d = 0.14 SD), possibly due to an emotional crossmodal association mechanism. Liking of characteristic sounds differed between the first and last annotations that the respondents had made (d = 0.21 SD), which might be due to an initially positive bias being countered by exposure to a task inducing a mode of critical listening. We believe that the SSR taxonomy will be useful for field research and simulation design. The empirical findings might inform theory, specifically research charting the perception of sound sources in multimodal environments.
|
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| 46. |
- Lindborg, Per
(author)
-
A taxonomy of sound sources in restaurants
- 2016
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 110, s. 297-310
-
Journal article (peer-reviewed)abstract
- Restaurants are complex environments engaging all our senses. More or less designable sound sources, such as background music, voices, and kitchen noises, influence the overall perception of the soundscape. Previous research suggested typologies of sounds in some environmental contexts, such as urban parks and offices, but there is no detailed account that is relevant to restaurants. We collected on-site data in 40 restaurants (n = 393), including perceptual ratings, free-form annotations of characteristic sounds and whether they were liked or not, and free-form descriptive words for the environment as a whole. The annotations were subjected to cladistic analysis, yielding a multi-level taxonomy of perceived sound sources in restaurants (SSR) with good construct validity and external robustness. Further analysis revealed that voice-related characteristic sounds including a 'people' specifier were more liked than those without it (d = 0.14 SD), possibly due to an emotional crossmodal association mechanism. Liking of characteristic sounds differed between the first and last annotations that respondents made (d = 0.21 SD), which might be due to an initially positive bias being countered by exposure to a task inducing a mode of critical listening. Comparing the SSR taxonomy with previous classifications, we believe it will prove useful for field research, simulation design, and sound perception theory.
|
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| 47. |
- Lindborg, PerMagnus, 1968-
(author)
-
Psychoacoustic, physical, and perceptual features of restaurants : A field survey in Singapore
- 2015
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 92, s. 47-60
-
Journal article (peer-reviewed)abstract
- Sound is a multi-faceted phenomenon and a critical modality in all kinds of sevicescapes. At restaurants, our senses are intensively stimulated. They are social places that depend on acoustic design for their success. Considering the large economic interests, surprisingly little empirical research on the psychoacoustics of restaurants is available. Contributing to theory building, this article proposes a typology of designed and non-designed sonic elements in restaurants. Results from a survey of 112 restaurants in Singapore are presented, with a focus on one element of the typology, namely interior design materials. The collected data included on-site sound level, audio recordings from which psychoacoustic descriptors such as Loudness and Sharpness were calculated, perceptual ratings using the Swedish Soundscape Quality protocol, and annotations of physical features such as Occupancy. We have introduced a measure, Priciness, to compare menu cost levels between the surveyed restaurants. Correlation analysis revealed several patterns: for example, that Priciness was negatively correlated with Loudness. Analysis of annotations of interior design materials supported a classification of the restaurants in categories of Design Style and Food Style. These were investigated with MANOVA, revealing significant differences in psychoacoustic, physical, and perceptual features between categories among the surveyed restaurants: for example, that restaurants serving Chinese food had the highest prevalence of stone materials, and that Western-menu places were the least loud. Some implications for managers, acoustic designers, and researchers are discussed. (C) 2015 Elsevier Ltd. All rights reserved.
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| 48. |
- Liu, Xiaowan, et al.
(author)
-
Measurements and modelling of dynamic stiffness of a railway vehicle primary suspension element and its use in a structure-borne noise transmission model
- 2021
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 182
-
Journal article (peer-reviewed)abstract
- The noise inside railway vehicles is transmitted by both structure-borne and airborne paths and, although there are many sources, the rolling noise is often the most important. This paper focuses on the structure-borne transmission of rolling noise in a metro vehicle. Measurements are presented first of the vertical and lateral dynamic stiffness of a primary suspension element consisting of conical rubber/metal elements. Results are presented for various constant preloads over the frequency range 60600 Hz. An analytical model of the suspension element is also developed, based on a mass-spring system and including wave motion within the rubber elements. The dynamic stiffness results are used in a finite element model of the running gear, consisting of the bogie frame, wheelsets and suspension elements. The excitation is provided by the combined wheel/rail roughness at the contact point. This model is used to calculate the blocked forces at the connection points between the secondary suspension elements and the car body. The blocked forces are combined with measured vibro-acoustic transfer functions from these mounting points to the vehicle interior to determine the structure-borne noise inside the vehicle. The proposed methodology is validated against measurements during operation in terms of acceleration levels, blocked forces and structure-borne noise levels inside the vehicle, showing reasonably good agreement. Including the dynamic stiffness for the primary suspension leads to improved agreement between 100 and 500 Hz compared with using a constant stiffness.
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| 49. |
- Ljunggren, Fredrik, et al.
(author)
-
Airborne sound insulation between dwellings, from 50 vs. 100 Hz : a compilation of Swedish field surveys
- 2018
-
In: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 133, s. 58-63
-
Journal article (peer-reviewed)abstract
- It has for long been debated whether 50 or 100 Hz is the proper lower frequency limit when evaluating airborne sound insulation between dwellings. Although 100 Hz is the lowest third-octave band within most regulations, there is an ongoing interest in paying more attention to lower frequencies. In Sweden, evaluation from 50 Hz became mandatory already in 1999 wherefore unique experiences are available by now. In this paper, extensive data in terms of field measurements and questionnaire surveys from in total 46 building objects of various constructions have been compiled. A number of single number quantities, standardized by ISO as well as alternatives, are compared concerning their correlation against the subjectively rated annoyance responded by the residents. The statistical evidence for a 50 Hz limit was found to be small considering the total database but when the lightweight buildings were analyzed by their own, the importance of frequencies below 100 Hz became clearer. The overall recommendation is to include frequencies from 50 Hz in order to achieve good sound protection against a broad variety of sound sources, including music and other possible items generating low frequencies.
|
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| 50. |
- Ljunggren, Fredrik, et al.
(author)
-
Correlation between sound insulation and occupants’ perception : Proposal of alternative single number rating of impact sound
- 2014
-
In: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 85, s. 57-68
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Journal article (peer-reviewed)abstract
- Traditionally, multi-family houses have been constructed using heavy, homogenous materials like concrete and masonry. But as a consequence of the progress of lightweight building systems during the last decades, it has been questioned whether standardized sound insulation evaluation methods still are appropriate.An extensive measurement template has been applied in a field survey where several vibrational and acoustical parameters were determined in ten Swedish buildings of various constructions. In the same buildings, the occupants were asked to rate the perceived annoyance from a variety of natural sound sources. The highest annoyance score concerned impact sounds, mainly in the buildings with lightweight floors.Statistical analyses between the measured parameters and the subjective ratings revealed a useful correlation between the rated airborne sound insulation and Rw′+C50–3150 while the correlation between the rated impact sound insulation and Ln,w′+CI,50–2500 was weak. The latter correlation was considerably improved when the spectrum adaptation term with an extended frequency range starting from 20 Hz was applied. This suggests that frequencies below 50 Hz should be considered when evaluating impact sound in lightweight buildings.
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