Underwater Calibration of Hydrophones at Very Low Frequencies from 30 Hz to 2 kHz

Abstract

An underwater hydrophone calibration system based on vibrating column method has been established in the National Metrology Centre, Agency for Science Technology and Research, (NMC, A∗STAR), the national metrology institute (NMI) of Singapore. It is used to determine sensitivities of hydrophones at very low frequencies ranging from 30 Hz to 2 kHz. The system is capable of calibrating hydrophones with measurement uncertainties less than 1.6 dB in the stated frequency range. This paper presents the methodology, system setup, measurement uncertainty evaluation, and performance validation. The system enables traceable underwater acoustic measurement at low frequency which has important applications in oil and gas exploration, defense technologies and ocean seismo-acoustic studies.