Multispectral and multiangle measurements of acoustic seabed backscatter acquired with a tilted calibrated echosounder.

A multispectral and multiangle analysis of seabed backscatter intensity has been conducted using data from a calibrated single-beam echosounder (SBES) with five frequency channels deployed over four homogeneous areas with different sediment types in the Bay of Brest (France). The SBES transducers were tilted at incidence angles from 0° to 70° to record the seafloor backscatter angular response at discrete frequencies ranging from 35 to 450 kHz. The recorded backscatter levels were analyzed for their angular dependence (average backscatter strength versus frequency and angle) as well as for their sample statistical distribution. The angle and frequency dependence of the seafloor backscatter obtained using a calibrated SBES can potentially be used to calibrate multibeam systems, and it can also help in elucidating the physical processes of backscatter controlled by the interaction between the acoustic wave characteristics and the sediment properties. Backscatter measurements for each area showed a consistent frequency dependence with little variation between the four sediment types.