• reversible hydrophone without an integrated amplifier;
  • used as receiver and transmitter tool;
  • wide-band analysis of poor signals;
  • observing the long-distance propagation of acoustic signals;
  • version options: underwater (immersible) or threaded.

POR (price on request)

Hydrophone BC 311 is a robust spherical compact hydrophone for absolute measurements of the sound spreading in actuating medium. The hydrophone has first-class characteristics in all geometry directions. It has omnidirectional characteristics in angular range, 270° wide in the x-z plane, and 360° in the x-y plane.


of BC 311 hydrophones

Hydrophone BC 311 - marine mammals studies


is used for measurements by being immersed into water on a cable


is used for measurements by cutting-in to the side of sealed vessel or pipe

Hydrophone BC 311 - control of sealed vessels or pipelines structural integrity, leak detection


of BC 311 underwater/threaded hydrophones

Labelling BC 311
Version underwater threaded
Nominal voltage sensitivity 65 µV/Pa 39 µV/Pa
Nominal charge sensitivity up 0,35 to 0,65 pC/Pa 0,22 pC/Pa
Sensitivity level (relative to 1V/µPa) -204 dB
Frequency band 3…100,000 Hz
Maximum value of measured sound pressure range 100 kPa
Maximum value of measured attenuating sound pressure range up to 10 MPa
Limit static line pressure* 60 MPa
Capacity exclusive of cable minimum 6 nF
Explosion-proof version upon request
Casing material stainless steel
Dimensions (length × casing diameter) 173 × ⌀23 mm 171 × ⌀23 mm
Coupling thread M20×1.5
Weight (without cable)
Cable standard length 10 m 2 m
Maximum cable length 250 m
Outer cable diameter 10.2 mm
Cable type Coaxial, with PVC coating, central wire, shielded, resistant to the environment with sulfuric acid
Cable connection BNC
Measurements operation medium water, air, oil and oil products, natural gas
Operation medium temperature 0…+60 °C
Environment air temperature −60…+80 °C

*The limiting hydrostatic pressure is indicated for the receiving element of the hydrophone and can be limited by the technical characteristics of the cable, in the case of immersion studies.


of BC 311 underwater/threaded hydrophones


  • sound spreading in water;
  • ultrasonic in a liquid medium;
  • noise in wet and polluted media;
  • sound in liquid and gas medium (laboratory and factory).


  • as calibration standard;
  • as sound projector


  • marine mammals sounds;
  • cavitation processes

Installation specifications

for threaded hydrophones ВС 311

The hydrophones are connected to special mounting seats, adapters, weldolets, etc.

Hex section of the hydrophone connection is used for installation of the hydrophone. It is not recommended to use any other parts of the hydrophone in the course of hydrophone mounting.

In order to maintain hermeticity of the hydrophone you can use additional plate included into the delivery scope (copper gasket). It is not recommended to use any other options (foam tape, plumbing hemp, etc), since it may negatively affect the hermeticity level.

Hydrophone BC 312 - mounting seat layout and dimensions

Mounting seat layout

Hydrophone BC 312 - mounting seat parameters

Example of threaded hydrophone installation


of BC 311 underwater/threaded hydrophones

Hydrophone BC 311 is connected to ZET 017 FFT spectrum analyzers over charge amplifiers ZET 420 (used as a projector) and ZET 440 (used as a measurement unit).

Using a submersible hydrophone as a measuring instrument

Use of a mortise hydrophone as a measuring instrument

When connecting Hydrophone BC 311 to the FFT spectrum analyzers of ZET 017 series using charge amplifier ZET 440, it is necessary to configure some settings in order to ensure proper operation of the system. Enter the “Settings” tab of Charge amplifier ZET 440 and set “×10” as the amplification ratio.

Enter the configuration parameters of the FFT Spectrum analyzer (connected to Charge amplifier ZET 440), enter the “Measuring channel” tab, and set corresponding sensitivity value specified in the product datasheet.

Hydrophone BC 311 - Device manager - Properties settings

Hydrophone BC 311 - Device manager - Main menu

Hydrophone BC 311 - Device manager menu - Measurimg channel properties window

Using a submersible hydrophone as a radiator

Use of a mortise hydrophone as a radiator


Frequency response characteristics of hydrophones BC 311 in receiver mode are shown in the chart.



The hydrophone BC 311 can operate as a sound projector as well as be used to measure sound spreading in liquid, and in the course of reciprocity calibration. The fact is that the hydrophone piezoelectric sensing element has a reversibility effect. Mechanical stimulation leads to forming of an electric signal and vice-versa —alternative current voltage applied to sensing element leads to stimulation of mechanical oscillations. The figure shows the hydrophone BC 311 frequency curves. The presented data refers to 1-meter radiation distance. The curve inclination is typical for hydrophones with piezoelectric sensing elements.


To determine sound pressure, produced by a hydrophone in projection mode at a 1-meter distance (with a definite level and a certain frequency signal applied to the input) you have to use the following formula:

m = 10n/20,

where n — hydrophone conversion ratio, dB relative to µPa/V per 1 meter (this magnitude is determined from hydrophone Frequency Response in projection mode);
m — the relation of projector generated pressure to voltage, µPa/V.
When 5V level 50 kHz signal is sent to hydrophone input, the sound pressure generated by the hydrophone in projection mode at a 1-meter distance is determined from hydrophone Frequency Response in projection mode as follows:

x/5 = 10127/20

x = 11.2 Pa


of BC 311 underwater/threaded hydrophones

The hydrophone is a piezoelectric transducer with sensing element made of ceramic piezoelectric materials. Sensing element and its inner supporting structure are firmly fixed in chloroprene rubber sound-transparent cap. Supporting casing is made of stainless steel, recognized for high strength, corrosion resistance, resistance to adverse environmental impacts and reliability in seawater. The hydrophone has no vulnerable metal parts.

Hydrophone BC 311 is a dynamic pressure transducer, it has even response curve throughout the whole range of the frequencies observed in any homogeneous medium, including air, sea and fresh water.


of BC 311 hydrophones

Hydrophone BC 311 is used to determine explosion pressure up to 1,000 kPa, pulse duration 2-5 ms (time sensitivity: around 0.1 ms).

Acoustic communication plays an important role in social life of whales. Ocean noise pollution (sonars, underwater blasts or water transport) is the main cause of marine mammals’ death since these factors are capable of injuring whales’ acoustic organs.

Acoustic research of marine mammals

Hydrophone BC 311 can be used as acoustic pressure primary transducer in the acoustic instruments and registration systems when observing marine mammals. Sound locators on the basis of Hydrophone BC 311 permit to detect vocalizing marine mammals, and to record sounds, produced by whales and dolphins.

This method is the most environmentally safe since sound locators located on sea-bed do not affect sea animals. Data obtained using such systems is sufficient for precise localization of any acoustic sources.

Research of acoustic field vector characteristics

using underwater/ threaded hydrophones BC 311

Nowadays application sphere of hydroacoustic research encompasses military use as well as the civil applications:

  • marine navigation safety control;
  • fishery and marine mammals industry;
  • mareographic research – seabed mapping;
  • exploration activities at ocean shelve;
  • localization of industrial noise sources, etc.

Let us consider the last item in more details.

Recently the use of complex recorders using vector-phase methods has become increasingly popular for the purposes of noise sources localization in hydroacostic field. The research of acoustic fields characteristics is based on methods of simultaneous recording of pressure field and pressure field gradient with the use of sound pressure transducers and vector transducers (oscillatory acceleration transducers, accelerometers, or seismoacoustic transducers) located at particular areas of the pressure field.

These methods are based on such basic notions as energy directional flux and velocity, energy density at a particular point of the environment, localization of energy flux (these notions have been thoroughly researched by theoretical physicist N. A. Umov, who has applied them to elastic body energy). In 1884 the notion of directional energy flux was introduced by J. Poynting, who used a directional vector notion in the description of energy propagation (this vector is commonly known as “Poynting vector”).

The structure of a combined hydroacoustic recorder is generally represented by a leak-proof sphere (its dimensions are negligibly small if compared to the wavelength). The sphere incorporates primary transducers: two hydrophones with external sensing elements used for pressure conversion (in this example – BC 311) and a triaxial vector seismograph used for recording of pressure gradient, oscillating velocity, etc. (in our case – seismograph BC 1313).

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