Subject: Re: 4 Hz modulation energy From: Erick Gallun <gallun(at)BU.EDU> Date: Thu, 24 Mar 2005 10:55:56 -0500Arthur, I would recommend first extracting the envelope by using either a halfwave rectification (i.e., replace all the negative values in the time waveform with zeros) or a Hilbert Transform and then lowpass filtering the waveform at around 50 Hz (the lowpass is optional if you only care about the 4 Hz component). Once you have the envelope, simply do an fft (making sure that your frequency resolution is at least 1 Hz) and look for the energy around 4 Hz. If any of these steps don't seem obvious too you, let me know and I can send you some Matlab code. Erick Gallun Postdoctoral Fellow Hearing Research Center, Boston University http://people.bu.edu/gallun At 03:30 PM 3/24/2005 +1100, Arthur Choi wrote: >Dear all, > > Could anybody tell me the method and the calculations on obtaining "4 > Hz modulation energy" for a speech signal? > >regards >Arthur