I understand all that, but what I don't remember is why there
is a 4KHz low-pass filter on voice lines. I know I've read the
reason before but I just can't recall what it was. Was it
simply arbitrary? A 4KHz upper limit is obviously sufficient
for voice quality. Did someone just pick that
It's the average frequency of human voice. if you look at a conversation on
a osciliscope, it averages out to 4k, so you double that and get the 8k
sample rate.
--
RFC 1149 Compliant.
""John Neiberger"" wrote in message
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> I understand all that, bu
27/02/2002 05:15 pm -
"John Neiberger"
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27/02/2002 03:17 pm
Please respond to "John Neiberger"
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Subject:Re: Re: Sample Rate [7:36566]--long reply [7:36566]
I understand all that
>All right, John--
>
>A couple of years ago (discreet cough), Cisco gave away copies of books as
>promos. One was _IP Telephony_ by Gorlaski and Kolon (McGraw Hill, 2000).
>GOOD BOOK. On pp 77-78 is an explanation of the Nyquist rate and voice
>sampling:
Well, if it comes from MANY years ago, bef
Two questions to prolongue the distraction:
1. If a 4KHz signal is sampled at 8Khz, it is sampled twice per cycle. Once
in the positive half and once in the negative. Doesn't this mean that the
value is dependant totally on the point at which it is sampled (and if you
sample it as it passes zero
The first question is pretty interesting. It seems that if you took a
1Hz signal and sampled it twice per second but you kept sampling the
points where the level was zero, it does at least seem possible.
However, that would only be with sine waves, not complex waves.
Still, it's an interestin
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