ASA 125th Meeting Ottawa 1993 May

4aAA2. Improved acoustical measurements with MLSSA.

Douglas D. Rife

DRA Labs., 24 Halifax Ct., Sterling, VA 20165

Two fundamental properties of MLS techniques, namely, phase randomization and energy conservation are exploited by MLSSA to achieve improved acoustical measurements. These include (1) the conversion of nonstationary interfering noise as well as weak nonlinear distortion into stationary noise and, as a consequence, (2) the possibility of correcting, as a post-processing operation, systematic errors in measured Schroeder decay plots whether due to interfering noise or transducer nonlinearities, (3) one-shot STI and RASTI measurements that properly account for contemporaneous background noise including nonstationary noise and, (4) the possibility of characterizing transducer nonlinear distortion by means of incoherency measurements that exclude, or at least attenuate, the contribution of the background noise. This last possibility is in contrast to traditional dual-channel coherence measurements that unavoidably lump together the effects of nonlinearity and noise. All of these results are demonstrated theoretically as well as experimentally using actual MLSSA measurements.