Car Silencer Design
Proceedings of ACOUSTICS 2005
9-11 November 2005, Busselton, Western Australia
General Design Principles for an Automotive Muffler
Potente, Daniel
Day Design Pty Ltd, Acoustical Consultants, Sydney, NSW www.daydesign.com.au ABSTRACT
This paper discusses the general principles of muffler design and explains the main advantages of various styles of mufflers. When designing a muffler for any application there are several functional requirements that should be considered, which include both acoustic and non-acoustical design issues as detailed in this paper.
INTRODUCTION TO AN AUTOMOTIVE
MUFFLER
with time. They have the ability to reduce noise at various frequencies due to the numerous chambers and changes in geometry that the exhaust gasses are forced to pass through.
The sole purpose of an automotive muffler is to reduce engine noise emission. If you have ever heard a car running without a muffler you will have an appreciation for the significant difference in noise level a muffler can make. If vehicles did not have a muffler there would be an unbearable amount of engine exhaust noise in our environment. Noise is defined as unwanted sound.
The down side to reactive mufflers is that larger backpressures are created, however for passenger cars where noise emission and passenger comfort are highly valued reactive mufflers are ideal and can be seen on most passenger vehicles on our roads today.
Sound is a pressure wave formed from pulses of alternating high and low pressure air. In an automotive engine, pressure waves are generated when the exhaust valve repeatedly opens and lets high-pressure gas into the exhaust system. These pressure pulses are the sound we hear. As the engine rpm increases so do the pressure fluctuations and therefore the sound emitted is of a higher frequency.
All noise emitted by an automobile does not come from the exhaust system. Other contributors to vehicle noise emission include intake noise,
9-11 November 2005, Busselton, Western Australia
General Design Principles for an Automotive Muffler
Potente, Daniel
Day Design Pty Ltd, Acoustical Consultants, Sydney, NSW www.daydesign.com.au ABSTRACT
This paper discusses the general principles of muffler design and explains the main advantages of various styles of mufflers. When designing a muffler for any application there are several functional requirements that should be considered, which include both acoustic and non-acoustical design issues as detailed in this paper.
INTRODUCTION TO AN AUTOMOTIVE
MUFFLER
with time. They have the ability to reduce noise at various frequencies due to the numerous chambers and changes in geometry that the exhaust gasses are forced to pass through.
The sole purpose of an automotive muffler is to reduce engine noise emission. If you have ever heard a car running without a muffler you will have an appreciation for the significant difference in noise level a muffler can make. If vehicles did not have a muffler there would be an unbearable amount of engine exhaust noise in our environment. Noise is defined as unwanted sound.
The down side to reactive mufflers is that larger backpressures are created, however for passenger cars where noise emission and passenger comfort are highly valued reactive mufflers are ideal and can be seen on most passenger vehicles on our roads today.
Sound is a pressure wave formed from pulses of alternating high and low pressure air. In an automotive engine, pressure waves are generated when the exhaust valve repeatedly opens and lets high-pressure gas into the exhaust system. These pressure pulses are the sound we hear. As the engine rpm increases so do the pressure fluctuations and therefore the sound emitted is of a higher frequency.
All noise emitted by an automobile does not come from the exhaust system. Other contributors to vehicle noise emission include intake noise,
References: Bies, D.A. and Hansen, C.H., (1996) Engineering Noise Control: Theory and Practice, 2nd Edition, E & FN Spon: Used For Calculating Transmission Loss In Silencer Systems, Applied Acoustics 64: 903-916 (2003) Mufflers, Applied Acoustics 44:99-116 : Great Britain (1995) Proceedings, 3-5 November 2004, Gold Coast Australia M.L.Munjal, (1987) Acoustics of Ducts and Mufflers, WileyInterscience. Potente, D, (2004) Drive Train Development for a Formula SAE Vehicle, Sydney University, Sydney. Applied Acoustics 60:425-450 (2000) Sahasrabudhe A Design of Expansion Chamber Mufflers Incorporating 3D Effects, Noise Control Engineering Journal 38 (1): 2738. (1992) Sadamoto, A Incidence Cases, Journal of Sound and Vibration 249(1): 165-187 (2002) Smith, P.H. (1965), Scientific Design Of Exhaust And Intake Systems