Reverberation Time Measurements in an Underwater Chamber With and Without a Pressure-Release Wall Covering.

摘要

A number of acoustic measurements were made for determining the reverberation time and absorption characteristics of an underwater chamber with and without a pressure-release wall covering. Several analysis methods are described which were investigated and found to be unusable due to limited transient response time of analog filters. A digital analysis method is described which overcomes the transient response time limitation of analog filters by using Fast Fourier Transforms to approximate the desired filtering characteristics. An interactive computer program is described which implements an algorithm for determining the slope of the acoustic decay and, hence, the reverberation time in a consistent manner using linear, least-squares curve fitting. The reverberation times measured with the pressure-release wall covering were on the order of 110 milliseconds, while the values without the wall covering were on the order of 30 milliseconds. The introduction of the pressure-release wall covering into the underwater chamber was found to reduce the average sound absorption coefficients to values acceptable for a reverberation chamber based on air acoustics standards. (Author)