Fibrous tangles are frequently used in loudspeaker enclosures to damp acoustic resonances that might otherwise occur. However, in addition to their attenuating properties, fibrous tangles also reduce the propagation speed of the sound waves, and this could also be used to reduce the dimension of labyrinth and horn-loaded enclosures. However, in order to use fibrous tangles in this way, it is necessary to be able to describe their effect on sound waves in a more precise way than is customary in designing loudspeaker enclosures. The present paper discusses a model of the interaction between sound waves and fibrous materials which seems to account for the main acoustic characteristics that are observed. The theory gives reasonable quantitative agreement with both the propagation speeds and attenuation rates obtained from experiments with a number of different fibrous materials, and an example is given of how the theory might be used in optimizing the use of tangles in a labyrinth type of enclosure. This is an example only, and the theory could also be used in designing other types of enclosures.
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