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Why do different sonar frequencies serve different purposes in undersea exploration?

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In undersea exploration, different sonar frequencies are utilized because the physical properties of sound in water—specifically attenuation and resolution—vary significantly with frequency. Researchers select specific frequencies to achieve different scientific objectives.12

High Frequencies (100 kHz or more): These are used in side-scan sonar to measure the texture of the seafloor. High-frequency, short-wavelength sound waves provide better resolution and reflect more effectively from small targets, allowing for detailed imaging.21
Medium Frequencies (approx. 12 kHz): These are typically employed for depth sounding to measure the distance from the surface to the ocean floor.2
Low Frequencies (3.5 kHz to less than 100 Hz): These are used to map the thickness of sediments in ocean basins. Because low-pitched sounds are absorbed and converted to heat more slowly than high-pitched sounds, they can penetrate deeper into the seafloor to reveal subbottom structures.21

Ultimately, the choice of frequency balances the need for detail against the distance the signal must travel, as higher frequencies are absorbed by seawater much faster than lower frequencies.12