[Asterisk-Users] Re: IVR GSM voice prompt quality

[John Fraizer]

Nik Martin wrote:

> With an app like audacity (open source sound editor) it's very easy to apply
> a high pass filter (start at 80-100 Hz or so) to make the files more audible
> on the 15kHz bandwidth of analog phone circuits
> 
15Khz of bandwidth?  Um, just currious.  Which telco would this be that 
is passing 15Khz of bandwidth?  The last I checked a typical analog 
circuit passed 300Hz - 3Khz (at least, that's what they're supposed to 
do).  That's 2.7Khz of bandwidth.  Where is the extra 12.3Khz of 
bandwidth that you mention coming from?

John