This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Acoustic Studies of Micro-Perforates for Small Engine Silencers
Technical Paper
2012-32-0107
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
To respond growingly strict environmental regulations the acousticians are challenging to develop novel types of silencing elements. There are different types of flow duct elements designed for silencing the pulsating gas flows into and out of fluid machines. The silencing effect is typically achieved by introducing acoustic reflection and absorption.
In order to achieve a good absorption in a wide frequency band, various fibrous materials e.g. wools are typically implemented. However, the physical properties of such materials do not often remain constant during the lifetime of a silencer. As the fibers tend to relocate and can partly be blown out to surroundings, acoustical performance may deteriorate. Therefore, it is in great interest to avoid fibrous materials in the design of the flow duct silencing elements.
The present work is focused on the modern type of absorptive acoustic element - a micro-perforated element. The absorption in micro perforated element is dominantly originating from the viscous effect inside the openings, non-linear acoustic vortex shedding and grazing flow iteration. To exert the advantages of this type of perforation, the opening dimensions have to be smaller than the thickness of the acoustic boundary layer i.e. in the sub millimeter range. Although different micro-perforated panels have been studied by several authors mainly for room acoustic applications, only a relatively few publications concerning the flow duct elements are currently available.
In this paper a number of different perforated elements including micro-perforates have been studied by varying the perforation shape and porosity. The studies have resulted in the development of micro perforated tubes with high absorptive properties. The micro-perforated tubes have successfully been implemented in the design of a Formula SAE racing silencer.
The scattering matrix elements, as well as the transmission loss are presented and analyzed for a variety of perforated tubes and the complete silencer.
The results exhibit a good potential for the micro-perforated elements developed. Also it has been demonstrated that this type of absorptive element can effectively substitute the conventional designs incorporating fibrous materials.
Recommended Content
Authors
Topic
Citation
Kabral, R., Rämmal, H., and Lavrentjev, J., "Acoustic Studies of Micro-Perforates for Small Engine Silencers," SAE Technical Paper 2012-32-0107, 2012, https://doi.org/10.4271/2012-32-0107.Also In
References
- Maa, D.Y. Theory and design of Microperforated-panel sound-absorbing construction Sci Sin XVIII 1975 55 71
- Maa, D.Y. Potential of microperforated panel absorber J Acoust Soc Am 104 5 1998 2861 2866
- Yairi, M Sakagami, K Morimoto, M Minemura, A. Acoustical properties of microperforated panel absorbers with various configurations of the back cavity Proceeding of ICSV12 Lisbon, Portugal 2005
- Tao, Z. Zhang, B. Herrin, D. Seybert, A. “Prediction of Sound-Absorbing Performance of Micro-Perforated Panels Using the Transfer Matrix Method,” SAE Technical Paper 2005-01-2282 2005 10.4271/2005-01-2282
- Toyoda, M. Takahashi, D. Sound transmission through a microperforated-panel structure with subdivided air cavities J Acoust Soc Am 124 6 2008 3594 3603
- Liu, J. Herrin, D.W. Enhancing micro-perforated panel attenuation by partitioning the adjoining cavity Applied Acoustics 71 2 2010 120 127
- Hillereau Syed, A.A. Gutmark, E.J. Measurements of the acoustic attenuation by single layer acoustic liners constructed with simulated porous honeycomb cores J Sound Vib 286 1-2 2005 21 36
- Wu, M.Q. Micro-perforated panels for duct silencing Noise Control Eng J 45 2 1997 69 77
- Allam, S. Abom, M. A New Type of Muffler Based on Microperforated Tubes J. Vib. Acoust. 2011 133 3 8
- Auriemma, F. Kabral, R. Rämmal, H. Lavrentjev, J. et al. “Acoustic Studies on Small Engine Silencer Elements,” SAE Technical Paper 2011-32-0514 2011 10.4271/2011-32-0514
- Bodén, H. Åbom, M. Modelling of fluid machines as sources of sound in duct and pipe systems Acta Acustica 3 1995 549 560
- Lavrentjev, J. Rämmal, H. Tiikoja, H. “The Passive Acoustic Effect of Automotive Catalytic Converters,” SAE Technical Paper 2011-24-0219 2011 10.4271/2011-24-0219
- Åbom, M. An Introduction to Flow Acoustics 164 2004
- Maa, D. Y. Microperforated panel at high sound intensity Proc. Internoise 94 1994
- Zou, J. Shen, Y. Yang, J. Qiu, X. A note on the prediction method of reverberant absorption coefficient of double layer micro-perforated membrane Applied Acoustics 67 2006