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Denny F
 
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Ric Oliva" wrote in message
...
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?


The term bit "rate" does contribute to the confusion. I think bit "depth"
would be better.

The quick answer is sampling rate (rate makes sense here) is directly
related to frequency response. Bit depth is directly related to dynamic
range.

According to the theory, your sampling rate needs to be twice the highest
frequency you want to record. So theoretically, 44.1 gives you 22kHz
response, which is beyond human hearing. In practice, the actual top end
limit will be somewhat lower due to analog filtering required to keep the
clock noise out of the audio. But still, anything over 44.1 is probably
superfluous rather than "better."

Each sample has to reflect the amplitude of the signal at that sample. That
value is stored in a digital "word." We're talking about storing the value
in either a 16-bit or 24-bit word. The more bits, the better the
resolution, which in audio is refered to as "dynamic range."

Another question - if I'm recording a project to audio CD, is it better to
just record at 16/44 since that's what the CD will be anyway, and I can

save
system resources? or should I do 24/48 and then dither it down,

essentially
changing what I originally heard? I read in the ProTools book by Berklee
Press that its best to record on LE using 24/44 since you won't hear much
difference between the 48k and 44.1k. Any insights into this?


24/44.

While your finished product can sound just fine to the vast majority of ears
at 16-bit depth, 24 is still worthwhile for recording, applying effects
(transforms) and mastering. The reason is that the greater dynamic range of
the 24-bit depth manifests itself in a lower "noise floor." This extra
"room" at the bottom of your dynamic range is valuable because each time you
perform any kind of transform to your audio signal(s), you'll add a bit of
noise due to rounding errors. A greater bit depth makes these errors
smaller, and when you resample or dither your final, mastered recording to
16-bit, most of those rounding errors will hopefully live in those truncated
bits.

That's not to imply that you can't do a fair number of transforms on a
16-bit file without seriously degrading it. But there is at least a good
argument for using greater bit depths for recording/editing. Moreso than for
higher sampling rates, anyway.

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Denny Fohringer
Itinerant guitarist
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Lessons and music:
http://surf.to/dennyf
Bands:
http://bluepearlband.com http://doubletakeband.com
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