Mid-frequency Active Sonar Sound

Description

Image of the USS Cowpens CG-63 in dry dock. The hull mounted mid-frequency sonar is in the bulbous projection at the bow. Photo by the U.S. Navy, public domain.

Mid-frequency active (MFA) sonars are used by navies around the world primarily to detect submarines. The U.S. Navy classifies MFA sonars as those that emit frequencies between 1 kHz and 10 kHz while some other countries classify MFA with different frequency ranges. One modern U.S. hull-mounted MFA sonar, the SQS-53C, is used on many U.S. Navy destroyers and frigates. The active sonar projector array is arranged in a curved geometry permitting a variety of transmit beams (for more about projector arrays see Technology > Projector Array). The SQS-53C sonar operates at 2.6 kHz and/or 3.3 kHz and often at a nominal source level of 235 dB (1µPa at 1m).

A sonar waveform with three sonar pulses. One pulse is a frequency modulated pulse (FM) and two are continuous wave pulses (CW), a 1 kHz bandwidth from 3 to 4 kHz and duration 2.5 sec. Image from Naval Information Warfare Center Pacific, Technical Report 6843, Figure 1. Note that the data in this figure is for illustrative purposes only and does not represent any real-world sonar signal.

MFA sonars produce a variety of sonar pulses which, for example, could be a single frequency tone (continuous wave), multiple frequency tones, or a frequency modulated pulse (upsweep or downsweep). Each sonar pulse type is designed for specific situations such as detecting movement or detecting an object in a reverberant environment.

Mid-frequency active (MFA) sonar signal transmitted during the Southern California (SOCAL) Behavioral Response Studies. Sound provided by Dr. Brandon L. Southall, Southall Environmental Associates.

Mid-frequency active (MFA) sonar signal recorded at a range of 1 km from the sound source during the Southern California (SOCAL) Behavioral Response Studies. This is what the signal would sound like to animals at a distance of 1 km from the transmitting vessel.Sound provided by Dr. Brandon L. Southall, Southall Environmental Associates.

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