A sox Question about the silence Module

["Martin McCormick" <martin.m@suddenlink.net>]

	I am not new to sox but I am asking to see if I have
missed something because a sox script I am using is mostly
working but not quite.

	I am attempting to remove long silent pauses in a
recording of people talking and what is supposed to happen is
that sound is recorded during voice or noises and the recording
should continue for a short period of time after the noise so as
to smooth out what one hears and make the conversation sound
more normal.  I test the script with a recording of 3 beeps with
dead silence in between of periods ranging from 4 or 5 seconds up
to a minute.  The silence parameters are such that one should
hear 3 beeps, each a half-second apart in the processed output.

	For those familiar with an electronic voice operated
relay or VOX, the delay is set to 1/2 second and there is where
the trouble is.  

	To get this effect, one sets a line of sox script as follows:

#! /bin/sh
sox -t .wav input.wav -t .wav output.wav silence -l 1 0 '-39d' -1 0.5 '-45d'

The field containing 0.5 which is the second-to-the-last  field
is the only thing that does not work.  The script records while
there is sound but the 0.5 seconds of blank recording after the
sound doesn't happen.

	What you hear are 3 beeps with a tiny gap in between that
never changes no matter what one sets that second-to-the-last
field to.  If you set it to a negative number, sox exits with an
error so it is reading that value, but there is no vox delay so
the actual recordings of conversation can sometimes sound a bit
odd as nobody seems to ever take a breath. One can set that
duration field to just about any number of seconds, minutes or
hours and all the silence in the 3 beeps recording is still just
a slight gap between each beep.  It never varies.

	Maybe one of you tried a script like this and got it to
work and can tell us what is wrong as I have been messing with
this script for a couple of days.

	The manual pages for sox and soxeffects state that the -l
flag is supposed to further smooth out the sound by recovering a
little bit of the silence that was there before the next sound.
It seems to also have no effect.

	Thanks for any good ideas.  It is almost good but not
quite.

Martin McCormick
WB5AGZ