You may want to try to use signal-correlated noise. ITU-T recommends on using Modulated Noise Reference Unit (MNRU) for this (please google it). I guess it is also available in ITU-T's standard tools library (?) (dont have refs at the moment). However, it is quite easy to implement it in Matlab. Signal correlated noise also affects the spectral envelope of the signal. As a matter of fact various researchers have endeavored to model its effect using measures such as cepstral deviation etc. Another way to induce spectral distortion in to the signal is to treat it with a codec (after all thats what codecs are good at (among other things)). Signal correlated noise is a feature of waveform codecs
(such as u-law compander etc).
----- Original Message ----
From: Faten B.A. <fatenpesq@xxxxxxxxx>
Sent: Wednesday, March 5, 2008 11:48:19 PM
Subject: [AUDITORY] speech degradation in a GSM network transmission
I want to introduce some artificial degradation to a speech signal in order to simulate speech degradation in a GSM network transmission.
The addition of a background noise seems to be simple but I don't know which type or noise distribution I have to use.
I want also introduce frequency degradation and I have no idea about the way this must be done.
Can anyone advice me or send me some documentations about this topic?