| 1. |
- Ahlinder, Sven, et al.
(författare)
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A study of parameters affecting noise on a heavy duty DI engine
- 2007
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Konferensbidrag (refereegranskat)abstract
- On a 13 liter Direct Injection Heavy duty diesel engine, noise and cylinder pressure have been measured in order to investigate if noise can be estimated from cylinder pressure. The idea of filtering cylinder pressure to obtain noise has been tested. This idea implies that the engine works as a linear filter. The linear relation between cylinder pressure frequencies and noise frequencies seems quite poor and the method probably does not work on the engine tested. When measuring noise, on the other hand, multivariate low order polynomials work well to study the trade-off between measured noise, fuel consumption, NOx and Soot. This implies that the huge datasets gathered with modern electronically controlled engines can be handled this way. Copyright © 2007 Society of Automotive Engineers of Japan, Inc.
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| 2. |
- Ahrens, Jens, 1978, et al.
(författare)
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Tutorial on scaling of the discrete fourier transform and the implied physical units of the spectra of time-discrete signals
- 2020
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Ingår i: 148th Audio Engineering Society International Convention.
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Konferensbidrag (refereegranskat)abstract
- The combination of the time-discrete property of digital signals together with the commonly employed definition of the discrete Fourier transform (DFT) can cause ambiguity when interpreting magnitude spectra with respect to the physical unit of the signal under consideration. Standardized scaling of spectra increases the comparability of frequency-domain data that are published in scientific articles or data sheets of commercial products. We present and discuss in this tutorial a collection of the most relevant scaling options for DFT spectra to yield amplitude spectra, power spectra, and power density spectra, and we illustrate how an implied physical unit of the underlying signal is reflected by the magnitude of the spectrum. The tutorial is accompanied by Matlab/Octave scripts that demonstrate the different cases.
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| 3. |
- Alves, Sonia, et al.
(författare)
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Urban sound planning - The SONORUS project
- 2016
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Ingår i: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 2319-2328
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Konferensbidrag (refereegranskat)abstract
- Sound is still insufficiently considered in most urban planning processes, resulting in unsatisfactory sonic environments that might even present health risks to citizens. No matter how complex and challenging the planning project might be, the creation or preservation of acoustically favorable environments should be part of urban planning. To support this process, the SONORUS project developed a holistic approach for urban sound planning and showed its benefits with practical test cases. The goal of the holistic approach is to facilitate the integration of sonic planning in an earlier stage of the planning process by combining different approaches and by providing new tools and methods, thus enabling urban planners to achieve healthy and supportive sound scenarios.
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| 4. |
- Amiryarahmadi, Nata, et al.
(författare)
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A virtual design studio for low frequency impact sound from walking
- 2021
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Ingår i: Acta Acustica. - : European Acoustics Association, EAA. - 2681-4617 .- 1022-4793. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Experience with wooden multi-storey houses have shown that impact sound insulation is one of most critical issues to ensure a good indoor environment. Even in cases where the impact sound insulation is fulfilled, people perceive the sound from e.g. walking neighbours as very disturbing. To investigate the subjective perception, a test facility is needed which allows for a coherent evaluation of different floor designs by listening test. The facility should ensure, that when comparing different floors, the same excitation by a walker and the same receiving room are involved. Only the floor design should be changed. As a consequence the spread in the data will only be due to the spread in the perception by subjects. In this paper a virtual design tool for low frequency impact sound insulation is presented, which consists of four parts; measured walking forces, floor models, an auralisation system which consists of a grid of loudspeakers simulating the vibration of the floor and a receiving room furnished as a common living room. In a pilot study a listening test is carried out for 13 different floors with different impact sound spectra at frequencies below 100 Hz. The results indicate that the judged annoyance strongly correlates with the judged loudness. However, there is a substantial spread observed in between the subjects participating in the listening tests. To understand this spread, a more extended study is needed with more participants and a classification of the subjects with respect to criteria such as noise sensitivity or age.
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| 5. |
- Amiryarahmadi, Nata, 1982, et al.
(författare)
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Application of LMS Algorithm to Measure Low-Frequency Transient Forces from Human Walking
- 2016
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Ingår i: Acta Acustica united with Acustica. - : S. Hirzel Verlag GmbH. - 1610-1928 .- 1861-9959. ; 102:1, s. 23-34
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Tidskriftsartikel (refereegranskat)abstract
- Measurement and modeling of low frequency ground reaction forces (GRFs) from human walking have been the subjects of research in different fields from biomechanics to civil engineering and structural dynamics. Many of the existing models are developed based on experiments which alter natural walking by for example presence of force transducers, limitations in the speed and path of walking and replacing the real floor with a transducerfacilitated measurement rig. These alterations result in contact forces which do not represent real GRFs. In this study, a time-domain inverse measurement method based on LMS algorithm is used to measure low-frequency (
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| 6. |
- Amiryarahmadi, Nata, et al.
(författare)
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Identification of low-frequency forces induced by footsteps on lightweight floors
- 2016
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Ingår i: Acta Acoustica united with Acustica. - : S. Hirzel Verlag GmbH. - 1610-1928 .- 1861-9959. ; 102:1, s. 45-57
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Tidskriftsartikel (refereegranskat)abstract
- Despite many advantages of wooden buildings, low-frequency noise disturbance, mainly from human footsteps on timber floors, is a major hindrance for widespread application of wood in multi-storey buildings. In many cases the impact noise evaluations of the wooden floors according to ISO 140-7 and ISO 717-2 standards do not correspond to subjective experiences. This study aims to investigate the characteristics of footstep forces to support further studies related to discrepancies between standard evaluations and low-frequency noise disturbances in lightweight buildings. Transient footstep forces in vertical direction made by different walkers and different footwear on two floor structures were measured and compared. The vertical footstep forces were then compared with the impact forces made by a standard tapping machine. Analysis revealed that footstep forces contain large amplitudes at low frequencies (20 < f < 50) which are not included in the standard evaluation procedure. Therefore, by extending the frequency range of the standard measurements down to 20 Hz and designing an accurate adaptation term for evaluations, a better correlation between standard impact noise evaluations and acoustic performance of the lightweight buildings might be achieved.
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| 7. |
- Amiryarahmadi, Nata, 1982, et al.
(författare)
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Time-domain model of a tapping machine
- 2011
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Ingår i: Proceedings - 6th Forum Acusticum 2011, Aalborg, 27 June - 1 July 2011. - 2221-3767. ; , s. 1713-1718
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Konferensbidrag (refereegranskat)abstract
- In the past few years the use of lightweight buildings made of prefabricated wooden elements has become more common. Ease of installation, high accuracy and lightness of such buildings has attracted builders and designers. Sweden, having a large coverage of renewable forests has an increasing interest in multi-storey wooden buildings. However noise and vibration in wooden buildings is an issue of concern especially low frequency impact sound due to footsteps. Impact sound insulation of floors can be measured based on ISO 140-7 using standardized tapping machine as excitation source. Experience has shown that in many cases the results obtained by this method do not correlate with annoyance experienced by inhabitants. On the other hand, the method presented in ISO 140-7 has usually shown to be relevant for the evaluation of impact sound transmission of concrete floors. Discovering the source of this contradiction requires deeper understanding of the impact process. A first step would be to find the difference between contact forces of the tapping machine on different floor materials. One could then correlate it with inhabitants’ perceived annoyance. This paper is the first step of this investigation which is a part of a Swedish research project called AkuLite. In this work a time-dependent model based on Hertz’s contact law is presented for the tapping machine. The model is validated by measurements on a homogeneous concrete floor. Also the contribution of parameters such as damping and stiffness of floor material on the resulting impact force and vibrations is studied.
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| 8. |
- Andersson, Patrik, 1974, et al.
(författare)
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A Method for Experimental Collection of Global Material Data for Tyres
- 2001
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Ingår i: Nordic Vibration Research 2001, Stockholm, Sweden (The Scandianvian Vibration Society, www.svib.se).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- For the modelling of the dynamic behaviour of tyres material data are required. Depending on the character of the model these will have different quality. Modelling with global structures such as beams or plates, representative data for the global bending stiffness, global mass etc. are needed. These data do not represent the details of the tyre structure but the combined properties of the structure. Therefore it is not possible to cut out samples of the tyre and determine the global material properties by measurements on these samples. Consequently it is necessary to estimate the material parameter by measurements carried out on the complete tyre. Results from such measurements will be related to the model used for the tyre (e.g. ring model, orthotropic plate, etc.). The material data obtained in such way are consequently a function of both the tyre structure and the model, which is used to update the data. A method for experimental collection of global material data for tyres has been developed. This method is based on the experimental characterisation of tyres by driving point and transfer mobilities and the use of the orthotropic plate tyre model for updating the material data.
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| 9. |
- Andersson, Patrik, 1974, et al.
(författare)
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A study of forces and noise generation in a contact including adhesive bonds
- 2004
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Ingår i: Nordic Vibration Research 2004, June 3-4, (The Scandinavian Vibration Society, www.svib.se).
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Konferensbidrag (refereegranskat)abstract
- Paper to be published.Adhesive forces are present in the contact between a road surface and a rolling tyre. Theses forces may add up to substantial adherence forces, causing stick-snap excitation of tread blocks, high frequency noise generation, and increased rolling resistance. An experimental setup was designed to study the process when a tyre tread block sample was pressed onto a road surface sample, and hastily removed. Time variation of contact forces and sound pressure were measured. The same situation was modelled using a time domain model of two elastic bodies in non-linear dynamic contact. The contact area is spatially discretised in contact points and the contact problem is solved using an elastic half-space. The response of the block is calculated by convoluting the forces with pre-calculated impulse responses of the same block, which is modelled as a mass-spring system. The adhesive bounds are included by allowing negative contact forces; the contact at a point breaks when the calculated contact force reaches a specified negative value. Typical results from the experimental setup and the model are presented. It is concluded that the experimental setup is suitable for investigating the detachment process of the tread block and that the model is able to qualitatively capture the contact force and noise generation.
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| 10. |
- Andersson, Patrik, 1974, et al.
(författare)
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Experimental Study of High Frequency Response of Tyres
- 2003
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Ingår i: EuroNoise2003, May 19-21 2003, Naples, Italy.
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Konferensbidrag (refereegranskat)abstract
- Most traditional tyre models concern the low and middle frequency ranges. It is necessary to include higher frequencies for improved accuracy in tyre/road interaction models. Often only the radial direction is included, although the tangential direction may be important, especially studying stick slip motion in the contact between tyre and road surface. Designing models requires insight into the behaviour of the tyre structure at higher frequencies. To add insight of high frequency behaviour, experimental studies were done on four different tyres with the same internal design but with different tread patterns. The results of this study underline the importance of the local deformation when forces act with small excitation areas on the tread. Adequate consideration of the tread properties in the tyre/road interaction models is thus of importance to obtain the correct local contact force distribution. This is most important for the tangential driving point mobility. Tread patterns are shown mainly to modify the flexural stiffness and mass in comparison to smooth tyres, while block resonances are not expected to be located in the frequency range in which tyre/road noise is important.
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