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Jay - atldigi
 
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article ,
wrote:

Peter Gemmell wrote:

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?


The way that finer resolution manifests is as a larger
signal to noise ratio. The noise is due to quantization and
the wider the sample, the lower the noise is relative to the
maximum representable signal. The noise is an approximately
random error of +-1/2 the value of the low order bit. It is
inescapable. It is intimately related to the dynamic range
because it determines how small the signal can be before it
loses signifigance relative to that error noise limit. The
ratio of how large a signal that can be represented to how
small a signal can be represented is the dynamic range.

In practice, I don't think that yet any front end to a 24
bit ADC is itself nearly as quiet as that quantization noise
so that you will see specifications, if they are honest,
that are signifigantly lower than the theoretical 144 dB SNR
that can be achieved with 24 bits.


Bob has it. Read his post and my post and you'll see that they are not
mutually exclusive.

White Sawn's satement seems to indicate that the extra bits are within
the same dynamic range, thereby giving you greater detail within that
range. You can't into the trap of viewing digital audio like it's
digital imagery. Unfortunately, 24 bits leaves the top 96db range of 16
bit alone, but lowers the noise floor and allows the recording of audio
events that are even smaller, at a lower level, i.e. below -96dB.

Rick understands that bit depth relates to amplitude and that DSP is
better with longer wordlengths. A small clarification is in order,
however. He seems to consider there to be extra headroom while
technically there is not, unless you change the zero reference. In other
words, increase the voltage that zero is referenced to. Nevermind
working at -10 or +4, you'll be using a new, nonstandard reference
voltage, and what about the analog electronics that probably can't
handle that voltage? You're asking for trouble for that reason and
several others (increasing the noise floor of the analog gear,
compatability, and more). Unless you want to do that, you really are
gaining what should be thought of as "footroom" more than headroom.

In practice some feel that you need to push a digital recording right up
to 0dB FS to "use all the bits". This really isn't as big an issue as
some would have you believe, as long as you use good gain stageing and
reasonable recording levels, especially with todays converters which
perform far better than much or the early crappy digital stuff. It
doesn't hurt to assumne that 24 bits gives you a little room to play
with, but unless you are recording a program with greater than average
dynamic range in a very quiet environment with excellent equipment and
minimal processing, you really aren't going to be able to take advantage
of those extra bits. Then again, they certainly don't hurt, and they
could help, so there's no reason not to. Still, it helps to understand
technically what's going on and when extra effort will pay off and when
if won't.

Some of these technical distinctions may not seem to matter much in
every day practice, but that's no reason to be uninformed. The lower
noise floor and extra dynamic range can really make a difference. Some
say it's "merely" dynamic range or "just" lower noise, like those things
are somehow unimportant and could hardly make a difference. It must be
something more esoteric that makes it sound better! Well, it's not.
Those things can be very important and it often does sound better. The
little details that were once buried below the noise floor may now be
audible, whether minute audio events or perhaps subtle overtones, and
the noise floor of the recording may be below your ability to hear it
anymore. That's not minced meat!

--
Jay Frigoletto
Mastersuite
Los Angeles
promastering.com
 
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