Apparatus and method for detecting sonar signals in a noisy environment

A sonar system, comprising:

• a sonar receiver and transmitter, or transceiver, for transmitting sonar signals and receiving sonar echoes over a range of operable sonar frequencies;
• dynamic selection means frequency, further comprising:
• means to periodically measure ambient noise levels for a plurality of frequencies within a range of available frequencies;
• means to dynamically select, from the plurality of measured frequencies, a sonar transmission frequency within the range of available frequencies which has an ambient background noise level that is lower than a predetermined threshold level, or that is lower than the other measured frequencies within the range of available sonar frequencies;
• and
• means to change the sonar transmission frequency to the selected sonar frequency,
• whereby, the sonar transmission frequency is dynamically changed on a periodic basis in response to changes in ambient background noise to avoid frequencies with high noise levels.