The approach to determine working frequencies of acoustic in-situ detector for seafloor hydrothermal fluid is presented. Based on the research of deep-sea noise and the sound generated by mid-ocean ridge black smoker hydrothermal vents, and on the hydrothermal-vent animal hearing ranges, coupled with influences of suspended particles of hydrothermal on acoustic attenuation under different frequencies, the optimal frequency range for detection of acoustical signal near black smokers is determined. The optimal frequencies providing the maximum ratio of receiver signal to background noise are obtained. We have developed a laboratory experimental setup for the optimal frequencies selection. In particular, we evaluated time-of-flight performance with respect to the source signal parameters of center frequency and bandwidth. The experimental results confirm the effectiveness of our approach. Current results indicate that individual transducers operated in the range of 18 - 25 kHz are immune to most interfering sounds and suitable for our system.
