Eco-active sonar concept with examples

Eco-active sonar is a term coined to describe high-frequency (>20 kHz) wideband (>20 kHz) active sonars that emit environmentally friendly transmissions without impacting the marine ecosystem. The remarkable biological sonar of dolphins is one example of eco-active sonar. The waveforms of the acoustic pulses projected by Indo-Pacific bottlenose dolphins (Tursiops aduncus) are reviewed and the observed fine structure of the bistatic scattering impulse responses of the sea floor, sea surface and scatterers in the water volume are presented. Another example is pulse compression sonar (commonly referred to in defense parlance as low probability of intercept sonar or covert active sonar) which transmit low source level, wideband coded signals of long duration in contrast to high source level, narrowband short-duration pulses of conventional naval sonars. Matched filtering of the sonar returns reveals the presence of echoes from undersea objects and monostatic reverberation contributions from the sea floor and sea surface. High-frequency, high-resolution sonar meets the need for enhanced situational awareness in the undersea littoral as well as precision navigation and high-resolution mapping of the sea floor. The advent of injection-molded piezocomposite wideband sonar transducers with quality factors approaching unity enable the practical realization of eco-active sonar.