Saclant Undersea Res. Ctr., Viale San Bartolomeo 400, La Spezia, Italy
The detection of transient signals by linear transform based detectors is investigated. The wavelet transform and the short-time Fourier transform are mainly considered. The wavelet transform is used here in its suboptimal time-frequency interpretation and is realized by a bank of nonorthogonal ``constant-Q'' filters. First, the performance of the wavelet detector is compared (by Monte Carlo simulations operating on synthetic data) to the performance of the short-time Fourier transform detector (STFT), the Wolcin detector, the matched filter detector, and finally the energy detector. The performance of the wavelet (``constant-Q'') detector and the STFT detector is shown to be almost comparable (however, the wavelet detector performs better with signals of wider bandwidths) but they are worse than the performance of the matched filter detector. The Wolcin detector, in this application, does not give the expected results and has poor performance, even for narrow-band signals. Then, the comparison of the performance of all the detectors is performed for real propagated transients (the same as those used in Monte Carlo simulations) transmitted by a sound source and received on a towed array in a deep water environment. The same conclusions as on synthetic data have been derived.