In Situ Measurement of the Absorption Coefficient Based on a Time-Domain Subtraction Technique with a Particle Velocity Transducer
Subtraction techniques for in situ measurement of the absorption coefficient have been proposed and tested using sound pressure signals. This paper is concerned with the subtraction technique based on the particle velocity measurement. In the method, the acoustic impulse response of the absorbing material surface under test is first measured with a particle velocity transducer, then the direct and reflected waves in the impulse response are separated by the signal subtraction technique in the time domain, and finally the absorption coefficient of the surface under test is obtained with a fast Fourier transform based post-processing algorithm. Three types of material have been tested in both a hemi-anechoic chamber and an office room: a perfectly reflecting plane, a thick polyurethane foam with high absorption property, and a thin polyurethane foam with medium absorption property. The absorption coefficient at normal incidence obtained from the method based on the particle velocity measurement has been compared with the result obtained from the method based on the sound pressure measurement. The investigation shows that the method based on the particle velocity measurement can be used to measure the absorption coefficient in situ and has better immunity to the disturbing reflections than the method based on the sound pressure measurement. However, its performance is sensitive to the vibration generated by the loudspeaker, which is not as prominent for the method based on the sound pressure measurement.
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Document Type: Research Article
Publication date: September 1, 2016
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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