The influence of bottlenose dolphin (Tursiops truncatus) click signal on the performance of underwater acoustic instruments

Abstract

Bottlenose dolphins (Tursiops truncatus) are gregarious marine mammals. They use powerful sonar system to communicate underwater and transmit click signals for echolocation. The impact of underwater noise on marine mammals has become major concern. The knowledge regarding the influence of marine mammals on underwater acoustic instruments were unknown. Since the frequency of bottlenose dolphins' click signals ranges from 120 Hz to 300 kHz, the peak source level of the click signals can be as high as 230 dB re 1pPa, and will overlap with the signal frequency of underwater acoustic instruments. This paper focused on the influence of bottlenose dolphin (Tursiops truncatus) click signal on the performance of an underwater acoustic instrument. Take Acoustic Doppler Current Profiler (ADCP) as the object of investigation for its being one of the most commonly used marine acoustic instruments, analyze the effect of bottlenose dolphins click signal on the detection of Doppler frequency shift and signal to noise (SNR) of ADCP. The study showed that when the frequency of bottlenose dolphins' click signals is equal to the working frequency of ADCP, the Doppler shift frequency measured by ADCP will be half of the actual value; when the SNR is less than 10dB for ADCP, the estimation of the average current velocity appears larger deviation than actual current velocity, when the SNR is less than −20dB, the estimated curve of the average current velocity can't be used to calculate the real current velocity.