Subject: Re: Frequency response was Re: [linux-audio-user] Audiophile CD's
From: Paul Winkler (pw_lists_AT_slinkp.com)
Date: Mon Jan 28 2002 - 20:22:55 EET
On Mon, Jan 28, 2002 at 10:18:07AM -0600, Ben Saylor wrote:
> I'm not sure how much greater than 2b f has to be, but apparently others
> have determined that 44.1khz or 48khz is high enough to reproduce
> frequencies up to 20kHz.
That's interesting, hadn't thought of it that way. I was always told
that 44k was chosen as a reasonable practical minimum that allows an
analog antialiasing filter to begin rolloff at or near 20 kHz and
reach infinite attenuation at the nyquist frequency.
I've always wondered why it's 44.1 and not 44 or 45 or whatever. I
just did a google search on this, and apparently it's because this
sampling rate became common when the only recording devices that could
handle that high of a rate was a VCR outfitted with an external PCM
encoding device. The 44100 rate somehow correspond in some way (don't
ask me) to the standard frame rates of the beta-format VCRs available
at the time. So it was a temporary convenience, with which we will
have to maintain backwards compatibility for quite some time to come!
The 32 KHz rate you see sometimes was chosen to allow slightly longer
recording times while providing enough high end for the 15 kHz
bandwidth of FM radio. 48 KHz was, like 44.1, chosen because of
compatibility with video devices.
--paul winkler home: http://www.slinkp.com music: http://www.reacharms.com calendars: http://www.calendargalaxy.com
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