The Topas parametric sub-bottom profiler family is based on low frequency sound generation due to non-linear interaction in the water column from two high intensity sound beams at higher frequencies.

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The resulting signal has a high relative bandwidth (~80%), narrow beam profile (close to the transmitted high frequency signals) and no side lobes. All these features results in very high spatial resolution in the sediment profiles. The narrow beam also results in lower received reverberation levels and thus higher penetration.