Could anybody tell me a method to calculate the "4 Hz modulation energy" for a speech signal?
I get some details : 4 Hz modulation energy: Speech has a characteristic energy modulation peak around the 4 Hz syllabic rate . We use a portion of the MFCC algorithm  to convert the audio signal into 40 perceptual channels. We extract the energy in each band, bandpass filter each channel with a second order filter with a center frequency of 4 Hz, then calculate the short-term energy by squaring and smoothing the result. We normalize each channel's 4 Hz energy by the overall channel energy in the frame, and sum the result from all channels. Speech tends to have more modulation energy at 4Hz than music does.