| 1. |
- Arvidsson, Emma, et al.
(författare)
-
Pattern and orientation of diffusers in rooms with an absorbent ceiling
- 2019
-
Ingår i: Proceedings of the 23rd International Congress on Acoustics : Integrating 4th EAA Euroregio 2019 - Integrating 4th EAA Euroregio 2019. - 2226-7808 .- 2415-1599. - 9783939296157 ; 2019-September, s. 2281-2288
-
Konferensbidrag (refereegranskat)abstract
- Lately have the demands on good room acoustics in public ordinary rooms increased. Traditionally has only reverberation time been considered in this type of rooms but complementary parameters as sound strength and speech clarity are more commonly used today. This trend naturally implies higher demands on the acoustic treatment. Typical for public ordinary rooms is to use an absorbent ceiling. One way to further improve the acoustic properties is to complement the ceiling treatment with diffusers. To investigate the effect of combining these two types of acoustic treatments have measurements been carried out combing different setups of diffusers in a reverberant room with an absorbent ceiling. The impact on reverberation time, speech clarity and sound strength has been studied. In this paper we present how diffusers can be used in order to improve the acoustic properties in a public ordinary room with an absorbent ceiling and how the pattern and orientation of diffusers can be used to adjust different acoustic parameters.
|
|
| 2. |
|
|
| 3. |
- Bayani, Mohsen, 1981, et al.
(författare)
-
Effect of temperature variation on the perceived annoyance of rattle sounds in the automotive industry
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. - 9783939296157 ; 2019-September, s. 4383-4390
-
Konferensbidrag (refereegranskat)abstract
- Product quality improvements and electrification in automotive industries, denote the growing need for squeak and rattle free cars. Studying the relation between main sources of rattle sound, like temperature changes and the emitted sound can help to improve the design robustness. In this research, the effect of temperature on the perceived annoyance level of rattle sounds that are generated from selected material pairs from the car cabin is studied. The sound stimuli were collected from a rattle test apparatus by binaural technology in laboratory condition, by a parameter study on temperature, gap and material pairs. Estimated annoyance levels, using the psychoacoustic metric developed through a subjective listening survey, show that perceived annoyance of rattle sounds varies differently for various materials in different ambient and boundary conditions. Employing this approach can lead to a rattle sound database for material pairs to be incorporated with geometry variation results for requirement setting and design robustness improvements in the early development phases of passenger cars before the physical prototypes are available.
|
|
| 4. |
- Bilbao, Stefan, et al.
(författare)
-
Local Directional Source Modeling in Wave-based Acoustic Simulation
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. - 9783939296157 ; 2019-September, s. 6377-6384
-
Konferensbidrag (refereegranskat)abstract
- Time-domain wave-based simulation approaches such as the finite difference time domain (FDTD) method allow for a complete solution to the problem of virtual acoustics over the entire frequency range, in contrast with the methods of geometric acoustics which are valid in the limit of high frequencies. They also allow for flexible modelling of sources and receivers, due to the inherently local nature of the computation, and complete access to the computed acoustic field over an enclosure. In this paper, a method for the emulation of sources of arbitrary directivity is presented, framed directly as an inhomogeneous wave equation. The additional terms in the wave equation take the form of Dirac delta functions and their distributional derivatives, and collections of such terms may be associated directly with an expansion of source directivity in terms of spherical harmonics. The local nature of the model implies a locally-defined efficient computational approach for wave-based methods defined over a spatial grid. Numerical results are presented.
|
|
| 5. |
- Vardaxis, Nikolaos Georgios, et al.
(författare)
-
Acoustic comfort assessment in heavyweight residential buildings : Acoustic data associated to subjective responses
- 2019
-
Ingår i: Proceedings of the 23rd International Congress on Acoustics : Integrating 4th EAA Euroregio 2019 - Integrating 4th EAA Euroregio 2019. - 2226-7808 .- 2415-1599. - 9783939296157 ; 2019-September, s. 836-843
-
Konferensbidrag (refereegranskat)abstract
- This article presents a study aiming to explore and evaluate acoustic comfort in residential multistory buildings in Sweden. Acoustic data was associated to self-reported responses acquired by a survey: a questionnaire was setup researching the response to noise annoyance from multiple sources in a flat and the emotional reactions of tenants to the acoustic climate at home. An assessment of acoustic comfort in the test apartments was performed utilizing the circumplex model of affect. A sample of 353 residents offered their ratings on 12 bipolar scales regarding their feelings towards their living sound environment. Two dimensions were identified: pleasantness and activation. Statistical models were developed using acoustic and structural variables. L'#$,&,'((predicted best pleasantness and number of flats per building predicted best activation. A new acoustic comfort indicator is suggested based on the pleasantness model and four novel acoustic comfort classes are proposed as: AC-1: Very good, AC-2: Good, AC-3: Acceptable, AC-4: No comfort.
|
|
| 6. |
- Andersson, Carl, 1992, et al.
(författare)
-
Minimum trap separation for acoustical levitation using phased ultrasonic transducer arrays
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 1117-1123
-
Konferensbidrag (refereegranskat)abstract
- Acoustic levitation for interactive visualizations is an emerging field which uses ultrasonic transducer arrays to induce radiation forces on small beads. To fully utilize the interactive and responsive aspect of the system, each bead must be controllable freely in the interaction space without interfering with the other beads. When beads are placed far enough apart it is possible to design a sound field that traps all the beads at their desired positions, taking any potential limitations of the hardware into account. The underlying physics limit how close in space two traps can be without interfering with each other. In this paper, we investigate the minimum spacing required between two beads for them to successfully and independently levitate in acoustical traps. Multiple methods for the sound field design are considered and compared with regards to the overall separation required as well as the gracefulness in the breakdown region.
|
|
| 7. |
- Forssén, Jens, 1968, et al.
(författare)
-
Prediction of quiet side levels in noise map calculations - an initial suggestion of methodology
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 4430-4437
-
Konferensbidrag (refereegranskat)abstract
- Urban morphology, i.e. shape and position of buildings in relation to streets, affects the distribution of noise and air pollution and can thus, through urban planning and design, be used to improve urban areas. This is of interest in an ongoing project where both air quality and noise are in focus. The present paper concerns the prediction of noise levels at positions of non-direct noise exposure such as noise levels at inner yard facades and values of noise contour maps at inner yards. With increasing densification, housing is built closer to the roads and the directly exposed facades receive higher noise exposure levels. The balancing effect of access to a quiet side is often counted on, supported by regulation, whereas the noise levels predicted using commercially available software are often incorrectly low at those points. A suggested methodology is described for how to combine the previously developed Qside model with a commercial noise mapping software to improve the prediction for non-direct noise exposure situations like essentially enclosed inner yards. We present also initial noise level results as outcome of a model study of varying building morphologies.
|
|
| 8. |
- Kropp, Wolfgang, 1959, et al.
(författare)
-
The application of dither for suppressing curve squeal
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 1551-1558
-
Konferensbidrag (refereegranskat)abstract
- Curve squeal is a highly disturbing tonal sound generated by vehicles like railways, metros or trams, when negotiating a sharp curve. The probability that squeal occurs increases with reduced curve radius of the track. Curve squeal noise is attributed to self-excited vibrations caused by stick/slip behaviour due to lateral creepage of the wheel tyre on the top of the rail. With respect to the enormous number of the rolling stock units and the long lifetime of waggons there is an urgent need for a cheap and simple retrofitting measure to reduce curve squeal. The main objective of the paper is therefore to investigate the potential to reduce curve squeal by means of active control in the form of dither in an efficient and robust way. Dither control has been applied in the field of mechanical engineering for systems including non-linear components. There it has been shown to suppress self-excited oscillations very efficiently. The control is an open loop control. It consists in adding a forced vibration to the vibrational system. The demand on this additional signal is that it is higher in frequency than the friction-induced response. From a physical point of view, dither control modifies the effective friction characteristic.
|
|
| 9. |
- Kropp, Wolfgang, 1959
(författare)
-
The influence of tyre cavity resonances on the exterior noise
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 475-482
-
Konferensbidrag (refereegranskat)abstract
- Rolling noise due to tyre/road interaction is mostly explained by tyre vibrations. The contribution of air-pumping might be an important contributor for certain cases. This observation has often been based on evaluating the speed exponent observed in measurements of the radiated sound. However simulations show that in many cases the observed speed exponent can be explained by tyre vibrations. In addition simulation show that for rough roads the resonances in the tyre cavity can play an important role. In the paper the influence of sound generation in the tyre cavity is discussed in more detailed. For this the Chalmers Tyre/Road Interaction model is utilized. The simulations clearly show the contribution of tyre cavity resonances to rolling noise as function of surface type. The results indicate that additional damping in the cavity would not only be beneficial for the interior noise inside the vehicle but especially for rough road also for the exterior rolling noise due to tyre/road interaction.
|
|
| 10. |
- Ottersten, Martin, 1981, et al.
(författare)
-
A new strategy of designing micro vortex generators to mitigate tonal noise generation from voluteless centrifugal fan
- 2022
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599.
-
Konferensbidrag (refereegranskat)abstract
- Low-speed voluteless centrifugal fans are typically used in ventilation systems. The negative side of the fans is noise, particularly tonal noise of which the dominant tone is at the blade passing frequency (BPF). One of the important noise contributors is the gap between the rotating shroud and the stationary inlet duct. Previous studies have shown that the flow passing through the gap causes turbulence that interacts with the blade leading edge (BLE), rendering surface pressure fluctuations that are the tonal noise sources at BPF. In this study, a method of assembling micro vortex generators (MVGs) to control the turbulence for voluteless centrifugal fans is proposed for the first time. The assembling is made in two different ways: 14 add-ons on the shroud surface at the gap, and 7 ones on the BLE surface near the shroud. The effects of the MVGs are investigated using the hybrid computational aeroacoustics method, which couples the improved delayed detached eddy simulation method with the Ffowcs Williams and Hawkings acoustic analogy. Our simulations show that the MVGs are effective to control the turbulence and mitigate the tonal noise. The assembled array of 7 MVGs achieves more reduction of the tonal noise than the 14-MVGs array.
|
|
| 11. |
- Thorsson, Pontus, 1974
(författare)
-
A parametric method to synthesize wind turbine sounds
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 1675-1682
-
Konferensbidrag (refereegranskat)abstract
- The annoyance to wind turbine sound is today well known. There is no doubt that increased sound pressure level causes in general an increased annoyance. However, when it comes to additional descriptors of the wind turbine sound, such as e g equivalent frequency spectrum or amplitude modulation, there is no consensus on what parameters that are most important. In the research project Wind Turbine Noise Effects on Sleep (WiTNES) there was a need for 8 hour long sound signals from wind turbines that were completely free of extraneous sounds. Recordings from reality are difficult to maintain free from disturbances. Instead a parametric synthesis method was developed that is capable of creating wind turbine sounds of arbitrary length. The sounds can be designed in terms of equivalent frequency spectrum, what frequency bands that have amplitude modulation as well as frequency dependent amplitude modulation strength and variation. Recordings of wind turbine sounds at immission distances from different wind turbine types were used to find relevant values for the parameters. This paper describes the synthesis method and some examples of input parameters.
|
|
| 12. |
- Autio, Hanna, et al.
(författare)
-
An attention-guided algorithm for improving the performance of acoustic simulations
- 2019
-
Ingår i: Proceedings of the 23rd International Congress on Acoustics : integrating 4th EAA Euroregio 2019 : 9-13 September 2019 in Aachen, Germany. - 9783939296157 ; , s. 2619-2626
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When performing acoustic simulations with the purpose of auralization, there is a trade-off between accuracyand speed. In real-time simulations of virtual reality, finding the balance of this trade-off is paramount to achiev-ing the desired result. If successful, the simulation speed is sufficient to provide a seamless acoustic experienceas the agent moves around the space, while still being accurate enough to be realistic. It is generally acceptedthat a 20ms update interval for the impulse response is sufficient for achieving proper interactivity in mostapplications. However, reaching this threshold without degrading the quality of simulation too badly can bechallenging indeed for complex scenes.In this paper, a compromise between interactivity (response time) and accuracy is suggested for raytracing simu-lations. This compromise mimics the behaviour of the listener or the agent, prioritizing speed or accuracy basedon how the agent behaves. When the listener is actively moving around the space, interactivity is prioritized.When the listener stands still, fully immersing in the experience, accuracy is improved. This is achieved byexploiting a fundamental truth of Monte Carlo simulations: Convergence improves with more samples
|
|
| 13. |
- Gaborit, Mathieu, et al.
(författare)
-
Off-line envelope estimation for acoustic screens with uncertain properties
- 2019
-
Ingår i: Proceedings of the International Congress on Acoustics. - : International Commission for Acoustics (ICA). - 9783939296157 ; , s. 1992-1999
-
Konferensbidrag (refereegranskat)abstract
- The development of new solutions to reduce impact of noise receives constant attention both from the research and engineering communities. Even though the proposed systems tend to diversify, multi-layered absorbers based on foams remain the most common. Such structures feature one or several thick slabs of foam and are completed by protective or tuning layers of small thickness inserted between slabs or on the free surface. These layers (acoustics screens or films) bring a number of challenges. Firstly, their thickness makes them hard to characterise and some parameters are uncertain. Secondly, the bonding to the surrounding system alter the effective properties. Given the strong influence the films have on the system's response, it appears important to account for these uncertainties from the design phase on. The present contribution introduces a new technique to efficiently account for uncertainty linked to the screens. More precisely, the proposed approach is based on separating the average film influence from the deviation due to uncertainties. This allows to estimate the response envelope using a pre-computed average response and the properties. The results computed for a range of typical and challenging configurations are promising and validate the robustness of the method at any angle of incidence.
|
|
| 14. |
- Persson Waye, Kerstin, 1959, et al.
(författare)
-
Acoustic intervention at preschools impact on children´s perception and response to high frequency sound qualities
- 2016
-
Ingår i: Proceedings of the 22nd International Congress on Acoustics, Buenos Aires, ICA 2016, 5 to 9 September, 2016. - 2415-1599. - 9789872471361
-
Konferensbidrag (refereegranskat)abstract
- At pre-schools personnel and children are known to be exposed to high sound levels. Tiredness and sound fatigue among the personnel are reported, while less is known about how children are affected. A previously developed interview protocol (INCH) was used to study the effect of an acoustic intervention at seven preschools. Before, 61 children aged 4-6 yrs were interviewed and 59 after. A reduction of the sound level in a range between 1 to 3 dB LpAeq was measured using stationary noise levels meters. The results were analysed using Generalised Estimating Equations accounting for repeated measure of the intervention. The results showed that a change in noise levels in the dining/activity room positively impacted on children’s perception of scraping and screeching sounds, frequency of reported tummy ache, and frequency of children reporting the teacher to speak with a raised voice. Perception of scraping sound per se, also impacted on angry reactions to scraping sounds, and children’s reporting on teachers speaking with raised voice. Although the intervention affected the noise levels only marginally, it seems to have influenced sound quality aspects related to the higher frequencies in the sound. The results are especially interesting given the new knowledge of children’s hearing.
|
|
| 15. |
- Ternström, Sten, 1956-, et al.
(författare)
-
Accounting for variability over the voice range
- 2019
-
Ingår i: Proceedings of the ICA 2019 and EAA Euroregio. - Aachen, DE : Deutsche Gesellschaft für Akustik (DEGA e.V.). - 9783939296157 ; , s. 7775-7780
-
Konferensbidrag (refereegranskat)abstract
- Researchers from the natural sciences interested in the performing arts often seek quantitative findings with explanatory power and practical relevance to performers and educators. However, the complexity of singing voice production continues to challenge us. On their own, entities that are readily measurable in the domain of physics are rarely of direct relevance to excellence in the domain of performance; because information on one level of representation (e.g., acoustic) is artistically meaningful mostly when interpreted in a context at a higher level of representation (e.g., emotional or semantic). Also, practically any acoustic or physiologic metric derived from the sound of a voice, or from other signals or images, will exhibit considerable variation both across individuals and across the voice range, from soft to loud or from low to high pitch. Here, we review some recent research based on the sampling paradigm of the voice field, also known as the voice range profile. Despite large inter-subject variation, the localizing by fo and SPL in the voice field will make the recorded values very reproducible within subjects. We demonstrate some technical possibilities, and argue the importance of making physical measurements that provide a more encompassing and individual-centric view of singing voice production.
|
|
