Patent ID: 6879544
Filing Date: 2005-04-12
Classification: G01V

Abstract:
1. A method of detecting manatee vocalizations, comprising the steps of: detecting sounds in an underwater region; generating a digital representation of said sounds; filtering out sounds at unwanted frequencies from said digital representation, wherein filtered data in a frequency range of interest is maintained; forming a plurality of overlapping time-windowed portions of said filtered data; estimating, for each of said plurality of overlapping time-windowed portions, a power spectrum for frequency bins in said frequency range of interest; normalizing, for each of said plurality of overlapping time-windowed portions, each said power spectrum for each of said frequency bins thereof using an average of power spectrums calculated over a plurality of said frequency bins, wherein a normalized spectrum value is defined for each of said frequency bins and wherein each said normalized spectrum value associated with broadband noise has a value that is less than each said normalized spectrum value associated with narrowband tones; providing a lowest resonant frequency of interest associated with manatee vocalizations, wherein said lowest resonant frequency has harmonics associated therewith; filtering out, for each of said plurality of overlapping time-windowed portions, normalized spectrum values indicative of narrowband tones that occur (i) in windows of frequency bins encompassing frequencies lower and higher than each of said lowest resonant frequency and said harmonics thereof and (ii) with a specified degree of variance with respect to frequency separation therebetween, wherein a resulting number of said normalized spectrum values indicative of narrowband tones are maintained; assigning, for each of said plurality of overlapping time-windowed portions, each said normalized spectrum value from said resulting number thereof to a frequency-based harmonic set, each of which is defined by a base frequency and resonances thereof; and applying, for each of said plurality of overlapping time-windowed portions, a scoring routine that uses each said normalized spectrum value in each said harmonic set wherein a manatee vocalization is indicated when a threshold score is achieved across at least a portion of said plurality of overlapping time-windowed portions.