Sound Absorption Measurements of Various Types of Grain
Insects destroy significant amounts of stored grain. To detect the sounds produced by insect activity inside the grain it is necessary to understand the absorption properties of sound in various types of grain. This paper describes some experimental investigations of absorption properties of sound in various types and heaped thickness of grain samples using the method of standing wave tube for the first time. The following conclusions can be drawn: (1) Grain is a highly absorbing acoustical medium. Sound is transmitted mainly in the passageways between the grain kernels. (2) Different types of grain have different absorption characteristics. For the same heaped thickness the larger grains have a smaller sound absorption coefficient than the smaller grains. Spherical kernels have a smaller sound absorption coefficient compared to non-spherical ones. The properties of sound absorption coefficient of grain depend mainly on the geometry and the size of the kernels and not on the solid matrix of the kernels. The average sound absorption coefficients of larger grains are smaller than the small grains in general. (3) The heaped thickness of the grain sample is an important factor affecting the sound absorption coefficient. The sound absorption coefficients at low frequencies increase when the heaped thickness of grain sample increases. The numbers of absorption peaks increase and the frequencies corresponding to the peaks decrease to the low frequencies when the heaped thickness of grain sample increases.
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Document Type: Research Article
Publication date: September 1, 2005
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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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