A quantitative relationship between geometry reconstruction inaccuracies and errors in the SPL correction for the Lloyd's mirror effect

Abstract

In attempting to calculate the spectral sound pressure level of an acoustic signal from measurements made in an underwater environment subject to surface interference effects, spectral amplitude correction techniques must be used. One such technique is based on the reconstructed source-receiver geometry. For the static situation in which the geometrical parameters are accurately known, a reliable correction can be made. For the dynamic case, however, in which there is a relative motion between the source and receiver, inaccuracies are likely to exist in determining the pertinent geometrical parameters such as source and/or receiver depths, source-receiver range, relative velocity, and sound speed. These inaccuracies translate directly into errors in the calculated sound pressure spectrum levels. The present analytical study quantitatively relates errors in determining the geometrical parameters to errors in the resulting Lloyd mirror corrections for the situation involving relative motion between the source and receiver. [Work sponsored by Naval Air Systems Command.]