----- Original Message -----
From: "Adam Atkinson" <ghira@mistral.co.uk>
Jay Ashworth wrote:
Now, those codecs *are* specially tuned for spoken word -- if you try to stuff music down them, it's not gonna work very well at all...
It was claimed to me many years ago that the 4kHz cutoff used in POTS serves women and children less well than it does adult males. I have never been aware that I have any greater problems understanding women or children on the phone than I do men, but my hearing is not great. I can't hear the difference between G.711 and G.729, for example, but some people can.
Googling "PCM adult male voice", "4kHz adult male" and similar isn't finding me anything. Was I told nonsense?
No, you weren't. A 4khz channel is generally good from 3-400hz up to about 3.4khz, and if you look at spectrograms of the various categories of voices you can see the differences, though they're not always as clear cut as you might expect: http://www.dplay.com/tutorial/bands/index.html In general, though, intelligibility comes from the higher frequencies, and 3.4kHz is *usually* high enough. What might be the case is that you'd have more trouble *distinguishing* amongst women, or between women and children, because the tones necessary for that are more located above the cutoff frequency. In short: it depends a lot on what you mean by 'serves well'. :-) Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://baylink.pitas.com 2000 Land Rover DII St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274