The performance of methods based on the fractional Fourier transform for detecting marine mammal vocalizations

The analysis of cetacean vocalizations is considered using Fourier-based techniques that employchirp functions in their decomposition. In particular, the paper considers a short-time methodsbased on the fractional Fourier transform for detecting frequency modulated narrow-band signals,such as dolphin whistles, and compares this to the classical short-time Fourier methods. The fractionalFourier technique explored computes transforms associated with a range of chirp rates andautomatically selects the rate for the final analysis. This avoids the need for prior knowledge of signal’schirp rate. An analysis is presented that details the performance of both methods as signaldetectors and allows one to determine their detection thresholds. These thresholds are then used tomeasure the detectability of synthetic signals. This principle is then extended to measure performanceon a set of recordings of narrow-band vocalizations from a range of cetacean species