The InterOcean Model R-130 and R-131 are high quality Hydrophones designed with an integral FET preamplifier and 6 dB gain and are used for general underwater sound pressure measurements.

They are characterized with an omnidirectional beam pattern, broad flat response, high sensitivity, and low noise, making them ideally suited as a secondary standard. The R-130/131 are adaptable to most existing amplifier and readout devices normally available.

The preamplifier has a 600-ohm dynamic output impedance, single-ended, which allows driving lower impedance cable without loss in sensitivity. The hydrophone is encapsulated in polyurethane with all exposed metal parts made from naval brass, providing high resistance to the corrosive action of seawater. The R-130/131 have given reliable and effective performance in a wide range of applications for many years.