An image processing approach to frequency tracking [application to sonar data]

A method for characterizing a signal´s narrowband content is presented. The scenario of interest is one in which the narrowband components are nonstationary, but persist for long periods of time, such as is found in many passive sonar and vibration analysis applications. This so-called frequency tracking problem-generally treated as a one-dimensional problem-is seen to reduce to that of extracting line structures from gray-scale images called spectrograms. Accordingly, the frequency tracking method presented is simply a line extraction technique based on standard image processing and machine vision methods and tuned to the type of line features and noise background present in spectrograms. Initial experiments using real sonar data indicate that the method outperforms currently used methods and has comparable computational cost