AM-FM Demodulation of Spectrograms using Localized 2D Max-Gabor Analysis
Tony Ezzat, Jake Bouvrie, Tomaso Poggio · 2007
We present a method that de-modulates a narrowband magnitude spectrogram S(f, t) into a frequency modulation term cos(Φ)(f,t)) which represents the underlying harmonic carrier, and an amplitude modulation term A(f,t) which represents the spectral envelope. Our method operates by performing a two-dimensional local patch analysis of the spectrogram, in which each patch is factored into a local carrier term and a local amplitude envelope term using a Max-Gabor analysis. We demonstrate the technique over a wide variety of speakers, and show how the spectrograms in each case may be adequately reconstructed as S(f, t) = A(f, t)cos(Φ(f, t)).