Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677
In underwater experiments in a tank, the usable test range is often limited by the size of the tank and reflections from the walls. To increase the test range, the tank must either be larger and/or the walls lined with absorbing material. This can be expensive. To find good low-cost absorption, 50-lb plastic sand bags filled with shredder rubber tires were tested. The absorption coefficient was measured in a tank lined with the bags. Using reverberation time, it was found that the absorption coefficient of the bags containing shredded rubber tires is about 0.7 in a frequency range of 5--25 kHz. A comparison is made with redwood wedges.