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Old November 16th 03, 04:59 AM
Peter Gemmell
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

Jay - atldigi wrote:
> In article >, "Ric Oliva"
> > wrote:
>>Ok, so I understand that 44.1k is 44,100 samples per second and 48k is
>>48,000 samples per second. Obviously 48,000 is better. I'm not exactly
>>sure what bit rate is though? CDs are 16 bit, DVDs are 24. What exactly
>>does that mean though?

> Article 1 and 2 deal with bit depth and dither, article 3 with sampling
> rates. Recording at wordlegths higher than 16 bit is helpful. In
> practice, 20 is almost always as good as 24 for recording since A to D
> converters don't have the dynamic range to capture 24 bits and the lower
> bits just contain the self noise of the box. For digital processing,
> however, you want to use longer wordlengths like 48 bit, or at the very
> least, 32 bit floating point.
> Most simply stated, wordlength (or bit depth) is dynamic range. Bit rate
> actually means something a little different, but we won't get into that
> right now as you obviously are asking about bit depth. For every bit you
> get about 6 dB (just over actually) of dynamic range. 16 bit CD has 96dB
> while 24 bit has 144. Extra bits do not add headroom; they add footroom.
> 0 dB FS (full scale) represents the same value in both 16 bit and 24 bit
> audio. The extra bits come into play at the bottom of the range. You are
> able to record smaller events - sounds at a lower level.
> In addition to dynamic range, it also means noise. in 16 bit, there is a
> noise floor of -96dB while 24 bit has a noise floor of -144 dB. 24 bit
> offers no additional accuracy in the top 96db of the dynamic range.
> Actually, an 8 bit recording is just as accurate as a 24 bit recording
> from 0dBFS to -48 dB. The -48 dB noise floor is quite obtrusive and the
> 8 bit recording certainly sounds worse, but those top 48 dB are just as
> accurate as a 24 bit recording. If you took a 24 bit file and added 96
> dB of noise, it would sound like an 8 bit file.
> Invariably any discussion of bit depths must eventually include dither.
> This, however, I'll leave to the tech talk articles I've pointed you to,
> or to a google search for the many posts that have appeared here in
> r.a.p. Be aware, however, that there are some common mistakes made
> quite often when discussing these subjects, so avoid the myths.
> Sometimes common sense tends to fail you until you understand how
> digital audio truly works, so some things that seem to make intuitive
> sense at first are actually technical rubbish.

So, what answer is correct? Whiteswan, Rick Powell, and Jay have given
three answers that sound good but are mutually exclusive. I've been at
this a few years and I still don't know what is right. Does 24 bit give
greater resolution than 16 bit or does it merely give a larger dynamic
range without a finer resolution?