Time-Frequency Filtering Based on Spectrogram Zeros

For a proper choice of the analysis window, a short-time Fourier transform is known to be completely characterized by its zeros, which coincide with those of the associated spectrogram. A simplified representation of the time-frequency structure of a signal can therefore be given by the Delaunay triangulation attached to spectrogram zeros. In the case of multicomponent AM-FM signals embedded in white Gaussian noise, it turns out that each time-frequency domain attached to a given component can ve viewed as the union of adjacent Delaunay triangles whose edge length is an outlier as compared to the distribution in noise-only regions. Identifying such domains offers a new way of disentangling the different components in the time-frequency plane, as well as of reconstructing the corresponding waveforms.