is used for measurements by being immersed into water on a cable
of BC 311 hydrophones
of BC 311 underwater/threaded hydrophones
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.
Example of threaded hydrophone installation
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.
BC 311 HYDROPHONES OPERATION IN RECEIVER MODE
Frequency response characteristics of hydrophones BC 311 in receiver mode are shown in the chart.
BC 311 HYDROPHONES: OPERATION IN PROJECTION MODE
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.
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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