Abstract
The TCIF algorithm [S. Fulop and K. Fitz, J. Acoust. Soc. Am. 119, 360–371 (2006)] was applied to a narrow band projector from the Shallow Water 2006 Hudson Canyon experiment. To observe Doppler shifts near CPA, short overlapping FFTs were formed from the measured time series data. The appearance of a secondary Doppler component indicates that the source was wobbling or fishtailing during the tow event. Analysis indicated the source was moving back and forth with amplitudes of about 6 in., at a rate of 1–2 cycles/s. Detecting these source dynamics required a basic FFT length less than 18% of the variable period and signal-to-noise ratio greater than 18 dB. Narrowband filtering the data significantly reduced interference from outside the band of interest. The FFT lengths were so short the frequency bin spacing was much greater than the wobble frequency variation, yet TCIF permitted the source wobble period to be observed. [Work supported by IR&D.]
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