# obtaining “4 Hz modulation energy”

Could anybody tell me a method to calculate the "4 Hz modulation energy" for a speech signal?

Thanks.

EDIT

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.

• Can you give a reference as to where this terminology is used? Does this help? – Peter K. Apr 25 '13 at 19:48
• I already checked this link but it did not give me a big push – Maystro Apr 25 '13 at 19:56
• Does my additional information start "pushing" ? :-) – Peter K. Apr 25 '13 at 20:00

So, what that means is you need to take your speech $s[n]$ and find the envelope:
$$e[n] = \left | s[n] + j{\bf H}\left[s[n]\right] \right |$$
where ${\bf H}$ is the Hilbert transform of your speech signal.