adamdea;578475 Wrote:
> I think the point that was being made [and at this point I pause to
> stress that it is not my point but i am telling you what i think the
> point is]
> was that if you isolate the recording of a quiet sound maxing 7 bits
> above digital noise floor, then this would be the same as a 7 bit
> recording of this sound alone using the full dynamic range of the 7
> bits. You may say that all 16/24 bits represent the quiet sound, but
> there are only 7 bits worth of possible values representing this quiet
> sound [I am not quite sure this is the case]. If the quiet sound had
> been made much louder then it would have had the benefit not only of
> being at a higher level but having been captured with greater
> precision.
>
> If you assumed that the analog sytem would be able to resove that low
> level noise with infinite resolution (on the assumption that analog
> recording works like an optical zoom rather than a digital zoom
> [provocative or what]) then the analog recording of this sound would be
> better.
OH - and I thought you were about to understand! :-)
1) all 16/24 bits represent the quiet sound, same as they do a loud
sound. The fact that several of them are zero makes no difference
except to the SNR. You have to stop thinking about "bits" as things in
their own right. They aren't - they are just part of a "word" that
represents the level (loudness) of something when you add ALL of the
bits together.
2) You also have to leave behind the digital photography analogies
because they aren't helping you to understand at all. In photography
each pixel is equivalent to a sample and has a bit-depth. BUT and it is
a MASSIVE "But"... when you look at a digital image you see all the
"samples" at once fixed in time, whereas in audio the sound is produced
by a variation in amplitude over time - that's all sound is! So in
audio, it is the change over time that matters. This is why pictures
get "blocky" when you zoom in - eventually you can see individual
samples - which make no visual sense in isolation.
There is NO equivalent to this in audio - without special tools (DSP)
you can't alter the timeframe in which you hear the sounds - and the
sounds themselves change (in pitch and duration) if you try. You can't
hear a single audio sample - in isolation it has no "sound". You can
see a pixel.
3) I don't think you've grasped the meaning of precision vs resolution
yet. In your 7-bit example, there are NOT only 7-bits worth of values
to represent the sound... 7-bits is just what it takes to represent the
LOUDNESS of THAT sound. The fact that the higher bits have zeroes in
them doesn't mean anything for the quality of the sound other than it
is quiet so you have more chance of hearing the noise floor intrude
into it.
If the quiet sound was made louder it would be captured with the same
precision, but a greater SNR.
{upper case for emphasis]
IN LINEAR PCM, RESOLUTION IS A FIXED PRODUCT OF BIT-DEPTH. It does not
vary with volume.
In lossy compression (MP3 et al) bit-depth...and thus
resolution...varies.
4) Your optical vs digital zoom analogy is not provocative - merely
wrong :-)
Analogue sources do NOT have infinite resolution. Nor do our ears, in
fact - but that's way OT.
Tape is limited by several things, including the tape speed, tape
width, tape head gap and magnetic particle size, all of which culminate
in a finite resolution. Likewise, vinyl is ultimately limited by the
physics of both the cutter head, the replay stylus, the pressing
process and the material properties of the final vinyl - all of which
limit the accurate recording of tiny (quiet) details.
I'll casually ignore the fact that most vinyl is cut from digital
masters in the last 20+ years... :-)
Replaying quiet sounds is NOT the same as recording with less bits!
Try the SB volume control - as you wind the volume all the way down the
sound doesn't get nasty & grittier like a pixellating image - it gets:
1) quieter
2) noisier
3) eventually some of the quietest parts will no longer be audible...
just like they would with any analogue source... this is simply because
they are too quiet to be heard, both in relation to the noise floor and
to the loudest parts.
--
Phil Leigh
You want to see the signal path BEFORE it gets onto a CD/vinyl...it
ain't what you'd call minimal...
Touch(wired/XP) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF
Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x
LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend
Supertweeters, Blue Jeans Digital,Kimber Speaker & Chord Interconnect
cables
Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything.
------------------------------------------------------------------------
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View this thread: http://forums.slimdevices.com/showthread.php?t=82050
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