AudioBanter.com - View Single Post - Reducing noise but keep speech

On Sat, 04 Oct 2003 01:03:58 GMT, (gmc) wrote:
You might also try a passband filter - eg brickwall out everything
except from 400Hz up to 2000Hz -get rid of some of the extraneous that
way..

This could be done relatively quickly in Sound Forge. It never hurts
to try different ideas. However, in my experience, if you set the
high frequency limit this low it will badly distort certain speech
sounds. "S"s suffer in particular. Cutting out the high frequency
components of an "S" make it sound more like a "th"... suddenly
everyone is talking with a lisp! When recording texts for use as
telephone announcements we used to limit the upper frequency to 4000Hz
in preperation to resample to 8kHz (T1 voice data rate is 8,000
samples/second). Depending on who was doing the voice, I would still
occasionally notice lisping.

Charlie Hubbard