Cellphones and Audio (was Ghost Click, though I got no idea why)

Jay Ashworth jra at baylink.com
Thu May 3 15:01:01 UTC 2012

----- Original Message -----
> From: "Adam Atkinson" <ghira at 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:


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'.  :-)

-- jra
Jay R. Ashworth                  Baylink                       jra at baylink.com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
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