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From: "Ronald C.F. Antony" <rcfa+logicaudio@...>
Date: Fri Feb 15, 2002 5:01pm
Subject: Re: [LUG] Re: [GEN] 24 bits vs. 96K

 >> Bit Rate determines dynamic range.  You will definitely hear mor of
 >> the soft
 >> sounds, and really loud sounds without compression when you use 24 bits
 >> instead of 16.  It is certainly a much more audible difference.
 >
 > I disagree with this. Bit depth has nothing to do with dynamic range.
 > Bit
 > depth has to do with resolution. A 16 bit converter and 24 bit converter
 > will clip at exactly the same point (provided they are accurately
 > calibrated). The difference is the quality of the quiter bits, providing
 > a more accurate depiction of the instrument being recorded.

Sounds like you have a different definition of "dynamic range" than
everyone else I know. More resolution in the Y-axis is the same
as "dynamic range". The point being, that you can *expand* a signal
until you have the same crappy definition for quieter bits as in a
standard 16-bit recording, and at that point 0dB will be a much
higher absolute SPL.

What is "accurately calibrated" is open to discussion. Since we do
not record absolute SPLs (otherwise we'd not have gain faders on
our preamps, and neither pads on the microphones, etc.) there is
now "absolute" standard for calibration.

Thus you can, depending on your equipment and gain settings, record
in 24-bit such that the least significant 16-bits end up with the
exact same values as a 16-bit recording, and what you get is 8-bit
worth of headroom, which corresponds to a factor of 256 on linear
scale, which I think corresponds to 24dB headroom, i.e. expansion
of the dynamic range.

To illustrate this in the graphical domain: if you go from a monitor
with a resolution of 640*480 pixels to one of 1280*960, you either
quadruple the resolution of the same image, or you can fit four times
as much information at the same resolution as before. It is the
combination dpi (dots per inch) setting and screen size which determine
which of the two (or what combination) is the case. The audio
equivalent to this are the SPL and gain settings in relation to the
bit depth.

Resolution and dynamic range are the flip sides of the same medal.

Ronald
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