A small microphone may be moved axially along the tube and Acoustic Impedence Tube position measured. The loudspeakers are fed with a common pure tone from a function generator and the sound waves pass along the tube to the sample. The Acoustic Impedence Tube consists of a transparent plastic tube fitted at one end with a glass reinforced plastic enclosure containing two loudspeakers and at the other with a heavy sample holder. The portion absorbed being converted into heat by the viscous action of the airborne wave as Acoustic Impedence Tube passes through the absorber. Dependent upon the type of material and the tone frequency, a portion of the sound energy is absorbed and the remainder is reflected back along the tube.
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