10120348INTERMEDIATE FREQUENCY HYDROPHONE TESTINGClosedCollaborative R&DInnovate UKMSEIS has developed their in-house underwater towed array, a device commonly used for marine mammal and environmental monitoring operations during offshore development or exploration. This type of monitoring operation is often strictly stipulated in offshore development licensing around the globe, to ensure the protection of marine mammal and other acoustically sensitive marine life from the impact of noise. The manufacturer is required to provide performance metrics for the equipment used to provide evidence in their specifications. This project aims to develop a system to perform in-house calibrations of hydrophone arrays in the frequency range 200 Hz to 2 kHz, a range known to be difficult to measure under free field conditions due to the extreme length of acoustic wavelength underwater. The proposed development involves a water-filled cylindrical chamber utilizing standing wave principles for uniform pressure calibration of underwater hydrophones. This technique aims to offer supplementary calibration at covering the 200 to 2000 Hz intermediate frequency range for comparison calibrations thus enhancing confidence and traceability, and supplementing data from readily available air pistonphones at frequencies below 250 Hz and from free-field measurements in tanks at kilohertz frequencies.