Estimating the flight parameters of a moving airborne source using one hydrophone

Abstract

The low frequency tone noise of the turboprop aircrafts can be discovered more easily under water than the broadband continuum spectrum noise due to its higher intensity. Ferguson and Lo provided a method based on a single hydrophone for estimating the four flight parameters, including the source frequency, velocity, altitude and CPA time (the time when the source passes the closet point of approach), using the variation of the instantaneous frequency (IF) of a single tone over time [Ferguson and Lo, IEEE J. Oceanic Eng., 24(4):424–435 (1999)]. Therefore, the performance of their method is largely determined by the precision of the IF estimates, which were obtained by using the short-time Fourier transform (STFT). In this paper, the polynomial chirplet transform (PCT), which models the change of the IF over time as a polynomial, is used instead of STFT to provide more accurate IF estimates. Moreover, multiple tones are used to improve the precision of the flight parameter estimates. The performance improvement is demonstrated by simulations and an experiment carried out near the Sanya coast in May, 2018.