The new ES333-7C and ES333-7CD are the first 333kHz transducers from Simrad of Norway. This new frequency has been introduced because different species and sizes exhibit different backscattering characteristics at different frequencies.

By combining data from this additional high frequency with the information obtained from other Simrad transducer frequencies (multifrequency studies), scientists will benefit from a more complete image.

"In order to observe smaller objects a higher frequency is required. This is because the wavelength of the sound needs to be similar to the dimensions of the backscattering object,” said Lars Nonboe Andersen of Simrad's Fishery Research department. “As the frequency increases, the wavelength decreases. Thus, this new frequency will aid the study of much smaller objects and species of marine life.”

The ES333-7C is made for mounting close to the sea surface on the vessel hull or on a drop keel. The ES333-7CD can be installed at depths down to 1,500 metres, for example on AUVs, towed bodies, or at the sea floor.

“Increased frequency causes higher “absorption” of the sound in the water, which results in decreased operating range. In order to benefit from the higher frequency you may sometimes want to move the transducer closer to the targets, so we decided to develop two versions of the new transducer, one for traditional use at sea level or just below and another for submerged applications," Mr Andersen said.

Simrad has used its composite materials to ensure its new transducers are able to operate over a large bandwidth. This enables the use of short pulses (high range resolution), without “ringing” or other deterioration of the pulse, which may affect the quality of the data gathered.