Low Frequency Transducers Posted by Business Development Manager March 8th, 2018

Low Frequency Transducers

Low frequency transducers are chosen for applications requiring long transmission ranges. These include underwater communications networks and sonar arrays. (Defence Research and Development Canada (DRDC) describes the use of barrel stave transducers for sonar applications.)

In the right conditions, in an underwater environment, low frequency sounds can travel thousands of kilometers. Low frequency signals suffer less attenuation than high frequencies. This is illustrated by Stokes’ law of sound attenuation.

SX01
barrel-stave flextensional projector (SX01)

Technical Specification

RESONANCE FREQUENCY
1.6 kHz & 9.5 kHz

BEAM ANGLE RADIAL 3DB AT FR
Omnidirectional

BEAM ANGLE AXIAL 3DB AT FR
Omnidirectional

DEPTH RATING
150 m

TRANSMIT VOLTAGE RESPONSE TVR
125 dB re 1 µPa/V @ 1m

SX05
dual barrel-stave flextensional projector (SX05)

Technical Specification

RESONANCE FREQUENCY
1.3 kHz & 5.5 kHz

BEAM ANGLE RADIAL 3DB AT FR
Omnidirectional

BEAM ANGLE AXIAL 3DB AT FR
Omnidirectional

DEPTH RATING
150 m

TRANSMIT VOLTAGE RESPONSE TVR
121 dB re 1 µPa/V @ 1m

SX53
low frequency bender transducer (SX53)

Technical Specification

RESONANCE FREQUENCY
750 Hz

BEAM ANGLE RADIAL 3DB AT FR
Omnidirectional (@ 750 Hz)

BEAM ANGLE AXIAL 3DB AT FR
Omnidirectional (@ 750 Hz)

DEPTH RATING
2 m

TRANSMIT VOLTAGE RESPONSE TVR
110 dB re 1 µPa/V @ 1m

Flextensional Transducers

Flextensional transducers produce low frequencies from small packages. Sensor Technology Ltd. offers Class I barrel-stave (SX01) and Class III double-barrel stave (SX05) flextensional projectors. Both designs transmit at low frequencies. The SX01 has its first resonance at 1.6 kHz and the SX05 at 1.3 kHz.

Typically sought for their low frequency and high output levels (TVR > 120 dB) barrel stave projectors also provide a wide operating bandwidth. The two models listed here span nearly four octaves.

DRDC provides a good comparison of generic Class I and Class III barrel stave transducer designs.

Flexural Diaphragm (Bender) Low Frequency Transducers

Flexural diaphragm transducers, also known as bender transducers, offer low frequencies from small packages. They produce among the highest output power of any type of transducer of similar size. In fact, comparing radiated output power to either transducer volume or mass, flexural diaphragm transducers have been shown to outperform barrel stave projectors. (See “Bender transducer design and operation” by John L. Delany)

However, of all the low frequency transducers produced by Sensor Technology, this design suffers from the lowest depth ratings. Some bender transducers have a depth rating of only a few metres.