Source characterization using recordings made in a reverberant underwater channel

The ability to accurately characterize an underwater sound source is an important prerequisite for many applications including detection, classification, monitoring and mitigation. Unfortunately, anechoic underwater recording environments required to make ideal recordings are generally not available. This paper presents a practical approach to source characterization when working in an imperfect recording environment; the source spectrum is obtained by equalizing the recording with the inverse of the channel’s impulse response (IR). An experiment was conducted in a diving well (depth of 5.18 m) using a logarithmic chirp to obtain the IR. IR length is estimated using methods borrowed from room acoustics and inversion of non-minimum phase IR is accomplished separately in the time and frequency domain to allow for a direct comparison. Results indicate that the energy of controlled sources can be recovered with root-mean-square error of −70 dB (10–70 kHz band). Two equations, one coherent and the other incoherent, are presented to calculate source spectral levels of an unknown source in a reverberant environment. This paper introduces a practical procedure outlining steps to obtain an anechoic estimate of an unknown source using equipment generally available in an acoustic laboratory.