MLS IMPULSE RESPONSE MEASUREMENTS FOR UNDERWATER BOTTOM PROFILING Angelo Farina

This work describes the use of the MLS (Maximum Length Sequence) signal for the measurement of impulse responses, in alternative to the traditional techniques based on the use of impulsive sources. The mathematical theory for the generation of the MLS signal and for the deconvolution of the system’s impulse response are first described. Then a software implementation of the measurement method, based on the creation of plug-ins for a shareware waveform editor on a low cost PC is demonstrated. Some preliminary experiments conducted under controlled conditions show that the proposed technique produces images of the bottom profile with higher signal-to-noise ratio and better spatial resolution than those obtainable with the impulsive technique. Furthermore, the new technique seems superior also for some practical aspects connected with the very nature of the MLS signals, which makes it almost inaudible and makes the sound source barely localizable: this is very important for military applications