Continuously Swept Technique for Measuring Sound Absorption

Measuring sound absorption using local field assumptions

This paper describes a novel three-dimensional sound intensity probe consisting of 8 MEMS (micro-electromechanical systems) microphones and a novel free-field calibration method. The use of MEMS-microphones allows for a very compact design compared to probes that employ 1/2-inch condenser microphones. A novel free-field calibration method, based on the principle of microphone interchange, is de...

The thermal pulse decay technique for measuring ultrasonic absorption coefficients

The classic method for measuring absorption coefficients ofmaterials requires adetermination of the temperature rise within a medium during ultrasonic irradiation. Serious errors may result from a viscous heating effect around the required thermocouple probe, and from heat lost by conduction to surrounding, cooler egions. A thermal pulse-decay technique is proposed and evaluated which allows fo...

Infrared Technique for Measuring Ultrasonic Absorption in Polycrystalline Metals

A numerical study of a method for measuring the effective in situ sound absorption coefficient.

The accuracy of a method [Wijnant et al., Proc. of ISMA 31, Leuven, Belgium (2010), Vol. 31] for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assumption, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical...

Development and Validation of Sound Transmission Loss Measurement System for Measuring Muffler Performance

Muffler is a part of the vehicle exhaust system that absorb or reflect sound waves to reduce exhaust noise. One of the most important determinants of a muffler performance is the amount of attenuation that has on its input wave; this parameter is known as sound transmission loss. Four - mic standard test is one way to determine this parameter which is used in this paper. In this study, a test d...