Hydroacoustic Monitoring

ISTI’s data acquisition, transmission, and authentication software modules have been embedded into hydroacoustic instruments manufactured by L-3 Communications Maripro and Leidos and used to monitor ocean waves by CTBTO and US National Data Center. Hydroacoustic monitoring involves recording signals that show changes in water pressure generated by sound waves in the water. There is one layer in the water where sound travel is slower but particularly efficient. This layer is the Sound Fixing and Ranging Channel, SOFAR, which is typically at a depth of about 1000 m. Hydroacoustic monitoring makes use of the unique phenomenon of sound waves being trapped in that layer. Hydroacoustic monitoring is one of four technologies used by the (IMS) to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Data obtained from hydroacoustic monitoring provide information on the location of a nuclear explosion underwater, near the ocean surface or near a coastline.