Line Array Hydrophone: Continuous and Discrete

BII's continuous/discrete line array hydrophones are designed for use in detection and search of sound sources underwater, passive SONAR, listening systems, near-field measurement and calibration.
BII-7021 and BII-7021Q are discrete linear array to support Digital or FFT Beamforming, and can be used as broadside and endfire array. The narrow beamwidth along the length provide direction information of the sound sources and reject the unwanted noises coming from other directions; the omnidirectional response cross the length covers large area to search. Two or four line arrays can be used to set up "T" or "+" type cross array functioning as a Target Angle Estimation System with Mills Cross techniques which provides accurate bearing information of sound sources.
BII-7022 averages sound pressures along the Line Array, and support built-in amplitude shading/weighting.
BII-7023 integrates the sound pressures along its surface and support amplitude shading/weighting. The integration of the sound pressures along a line can be used in measurement of acoustic radiation field, trouble-shooting, maintenance and development of transducers and arrays, and researches in theoretical acoustics such as boundary element acoustics, Green's function, Helmholtz integral and Rayleigh's integral, etc...
The body of BII-7020 series is streamlined hemispherical domes which minimize the drag forces and the hydrodynamic noise caused by the hydrophone in motion or the flow past the hydrophone.
For the array less than 15kHz, please refer to BII-7010 hydrophone or BII-7140 Hydrophone to set up discrete array.

BII-7020 Series Line Array Hydrophone

Suggested Application
Towed Array, Sonobuoy, PAM System Tracking of Acoustic Tags Direction-finding Sonar System Target Angle Estimation Systems Locating Marker/Pinger/Beacon/Transponder	Near-field Calibration and Measurement Hydrophone Calibration Trouble-shooting, Maintenance and Development of Transducers and Arrays Acoustic Pipeline Leak Detection Directional Communication
Related Products
BII-7010 hydrophone Low Noise Broadband Hydrophone	BII-7140 Hydrophone Acoustic Element for Array/Streamer/Beacon

Specification

Sensitivity Loss over Extension Cable (dB) = 20*log[Ch/(Ch+Cc)]. Ch: Hydrophone Capacitance; Cc: Capacitance of Extension Cable. Cable is of 100pF/meter roughly. Valid for hydrophone without preamplifier.

Line Array Hydrophone	BII-7021Q	BII-7021	BII-7022	BII-7023
Signal Processing:	None	None	Averaging of Sounds	Integration of Sounds
Operating Frequency:	1Hz to 10 kHz	1Hz to 25 kHz	1Hz to 160 kHz	1Hz to 160 kHz
Array Element Quantity:	Discrete, N; N ≤ 32.	Discrete, N; N ≤ 32.	Continuous	Continuous
Signal Output:	N	N	1	1
Element Spacing d:	≤ λ/2, Bespoke.	≤ λ/2, Bespoke.	0 mm	0 mm
Acoustic Aperture:	Φ31.8xL (mm): L=(N-1)*d	Φ24xL (mm): L=(N-1)*d	Φ9.5xL (mm)	Φ9.5xL (mm)
Beam Pattern:	Toroidal Shape	Toroidal Shape	Toroidal Shape	Toroidal Shape
Beam Steering:	Electronic or Software	Electronic	Mechanical or Manual	Mechanical or Manual
Along-length Beam Width:	No Shading: 2*arcsin(1.4*λ/(PI*L))	No Shading: 2*arcsin(1.4*λ/(PI*L))	No Shading: 76200°*kHz*mm/(f*L)	No Shading: 76200°*kHz*mm/(f*L)
Cross-length Beam Width:	Omnidirectional	Omnidirectional	Omnidirectional	Omnidirectional
Voltage Sensitivity: (Without Shading)	-189.4 dB V/μPa	-191.5 dB V/μPa	-200.0 dB V/μPa	-200.0 dB V/μPa
Output Type:	Differential	Differential	Differential	Differential
Element Capacitance:	2.6nF	3.7nF	0.225nF/mm*L	14.4nF*mm/L
Diameter ΦD:	Φ42mm	Φ33mm	Φ21mm	Φ21mm
Length (mm):	L+20	L+20	L+20	L+20
Cable:	Shielded Cable Bundles, Twisted Pairs.	Shielded Cable Bundles, Twisted Pairs.	Shielded Cable, Twisted Pair.	Shielded Cable, Twisted Pair.
Transmitting Sound:	No	No	No	No

Maximum Array Length:	Maximum array length BII can manufacture is 1.5m.
Shading/Weighting:	1. Default: No (Blank) 2. Dolph-Chebyshev (DC) 3. Binominal (BN)
Side Lobes:	1. No Shading: ≤-13.4 dB; 2. Dolph-Chebyshev: ≤-40.0 dB; 3. Binominal: No Side Lobe.
Receiving face:	Cylinder
Signal Conditioning:	Hydrophone Preamplifiers Not included, order separately. Signal Filter Not included, order separately.
Operating Depth:	300m, Maximum
Information:	Acoustic Components and System: Installation/Mounting, Ordering, Wiring, Array & Aperture Design and much more.

Technical note: for long line array, to avoid high pull force acting on the underwater connectors and the array cables, a reinforced rope with high pull strength shall be used along the array, and the array cables are tied on the reinforced rope with soft cotton rope (avoid scratching or damaging cable jacket). Make sure that ONLY reinforced rope withstands high pulling force during field operation. BII does not sell reinforced rope and soft cotton rope, which are usually available at buyer's local stores.

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