[ntp:questions] Accuracy of audio tones via VOIP

John Hasler jhasler at newsguy.com
Tue Jul 9 22:00:23 UTC 2013

Robert Scott wrote:
> That does not sound too encouraging for the pitch accuracy of tones
> transmitted over Skype.  Of course you would never notice it in normal
> speech, which is, I guess, all that Skype is targetting.  But for
> calibrating to the standard frequency tones from NIST (500 Hz and 600
> Hz), it probably is not trustworthy, right?

The waveform at your end of a Skype connection is not the one
that started from the other end.  It is something that the hardware at
your end generated based on instructions from the other end.  It is
intended to be close enough for you to not hear much difference.

Landline long-distance usually goes over packet-switched networks as
well these days.  Unless your call to NIST is local you probably aren't
hearing the tones they sent.

John Hasler 
jhasler at newsguy.com
Dancing Horse Hill
Elmwood, WI USA

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