Broadband match-field processing applied in a highly reverberant environment

Abstract

Application of matched-field processing (MFP) techniques to locate and identify broadband acoustic sources is of interest for studying low event rate cavitation and other hydroacoustic noise sources in water tunnels and other reverberant environments. Here, the main challenge lies in fully exploiting the potentially hundreds of kHz of bandwidth of the cavitation signal to refine the source location estimate. This presentation reports on the preliminary application of MFP in a reverberant enclosure that geometrically mimics the test section of a laboratory water tunnel. For this effort a sound projector and one to four hydrophones are used to make narrow-band and broadband sound field measurements within the enclosure. The requisite field model was initially based on a sum of modes assuming pressure release boundaries, but was empirically modified to accommodate finite impedance boundaries. The model modification allowed the enclosure’s impulse response to be accurately modeled from 3 to 11 kHz and the incoherent Bartlett processor to locate the source when it emitted a series of continuous single tone signals from 3 to 12 kHz. Extension of this effort to signal pulses, a ray-based field model, and water-tunnel testing and sea trials will be discussed as well. [Work sponsored by ONR.]