C55 Series Hydrophones

The Cetacean Research C55 series of hydrophones are preamplified, cylindrical hydrophones designed for the detection of infrasonic, audible, and ultrasonic sounds. Please note these hydrophones are available by special order only. For nearly all applications, we recommend using the C57-series hydrophones instead.

Cetacean Research™ C55 hydrophones are available by special order only. We recommend using the C57 instead.

Cetacean Research™ C55 Hydrophone

The C55 in Action!

January 2014 - Recording Engineers Tool

Listen to the recording made by a Cetacean Research C55 hydrophone and a DPA 8011 used as a stereo pair.

Raccoons in the Pool (electronic only)
3:11, 9MB, MP3
by Jozefius V. Rattus & SWARMIUS
read about the music

April 2013 - Deployed in the Pelagos Sanctuary

Watch (and listen) as French researchers listen to sperm whales in the Pelagos marine mammal sanctuary using a Cetacean Research C55 hydrophone. This video is an excerpt from a program that aired on Thalassa in April 2013. Thanks to Hervé Glotin.

September 2012 - Sea Lion Stomach Survival Testimonial

C55 hydrophone survives four weeks in Stellar sea lion stomach acid ... view pictures.

In addition to typical underwater use, the Cetacean Research C55 series hydrophones can be used for the detection of airborne and subterranean sounds and vibrations.

The C55, C55RS, and C55X hydrophones include an integral connector and are encapsulated in a very rugged polyurethane material. An extra-rugged version is now available: the Cetacean Research C57 hydrophone.

The hydrophones are not individually calibrated but calibrated frequency response measurements can be performed on request.

  • Cetacean Research™ C55 hydrophone
  • Cetacean Research™ C55 hydrophone with cable and battery box
  • Battery / Connector Box
  • Hydrophone Protection Cage
  • Frequency Response graph for C55
  • Frequency Response graph for C55RS
  • belugas-2011-c55-joe-lg
  • radiograph of C55 hydrophone in a sea lion stomach, taken September 2012
  • C55 hydrophone that survived a month in sea lion stomach acid
  • C55 hydrophone with bones to show scale

C55 series hydrophone specifications

C551 C55RS2
Linear Frequency Range (±3dB) [kHz] 0.015 to 44 0.015 to 50 & 124 to 250+
Usable Frequency Range (+3/-12dB) [kHz] 0.008 to 100 0.008 to 77 & 96 to 250+
Transducer Sensitivity* [dB, re 1V/µPa] -185 -200
Preamplifier Gain [dB] 20 20
Effective Sensitivity* [dB, re 1V/µPa] -165 -180
SPL Equiv. Self Noise at 1kHz [dB, re 1µPa/√Hz] 46 (Sea State Zero) 61
Power Requirement [Vdc] 5 to 32 5 to 32
RMS Overload Acoustic Pressure [dB, re 1µPa] 169 to 186 184 to 201
Maximum Operating Depth [m] 460 460
Operating Temperature Range [°C] -40 to 60 -40 to 60
Output Impedance [Ω] 10 10
Dimensions [mm] 110L x (25 to 16)dia. 110L x (25 to 16)dia.
Integral Connector *** Subconn MCBH3MSS Subconn MCBH3MSS

(1) The C55 hydrophone is a direct replacement for the C54XRS.

(2) The C55RS hydrophone is a direct replacement for the C54XR.

*  Transducer Sensitivity + Preamplifier Gain = Effective Sensitivity.
*** Connectors are rated to a depth of 7,000 meters; see below (or to the side) for mating connector and cables.

Shielded Cable Length [m]

  • mating connector molded to 15, 30, or 50 [m] shielded cable
  • other lengths available on a custom order basis
  • cable includes Integral Connector rated to a depth of 7,000 meters.

Battery / Connector box

Battery boxes are rated NEMA-4X water resistant. Standard signal connection for the Cetacean Research C55 series hydrophone is through a watertight female BNC connector with gold center contact. The hydrophones are powered by one or two 9V batteries (not included) or an optional long-life rechargeable, external power supply.

Signal Output Female BNC connector
Battery Life [hours] > 20
Box Dimensions [mm] 110 long (including connectors) x 90 wide x 50 high


  • omnidirectional below 10kHz;
  • very directional at high frequencies (e.g., ~15º solid angle at 200 kHz, –3dB);
  • directionality focused in a plane.