[colug-432] 24-bit Sound Input

[Dave Maxwell]

On Sun December 13 2009, vince at planetvince wrote:

> 2.  Audacity has a auto level function I've used.
> It looks at the entire file and then adjusts the level to the max with no
> clipping. Possibly this will eliminate the 24/16 bit issue.
>
> v

That is normalization and it should almost always be the final step of 
processing a given bit of audio.  It doesn't solve the issue because 16 bit 
audio at 44 or 48 kHz is a final destination format at "CD quality".  To get 
CD quality a given piece must be sampled such that the loudest peak in the 
piece is also the loudest sample that it is possible to take but no louder.  
In practice, this can't be accomplished.   You want that because you want the 
widest possible variation between the loudest and softest samples in your 
recording.  This is called "dynamic range".

That is why I would play a record side a time or three to get as close as I 
could before actually recording.  If however, I record and edit in 24 bit and 
set my levels such that I'm consistently hitting around 75% then I'm assured 
that I'm taking advantage of an amount of dynamic range that easily exceeds 
that possible in a 16 bit recording.  And I wouldn't need to be fiddly about 
it.  I only have to be consistently using in excess of 16 bits while sampling 
the audio.  If I normalize that THEN downsample to 16 bit I'll have a 
recording that will have both a reasonable filesize and excellent audio 
quality. 

In analog terms, a 24 bit/=>48kHz recording is pretty like using 1-inch audio 
tape at a fast speed.  If then master that down to an audiocassette, I'm 
assured of taking advantage of the maximum a Phillips cassette can offer.  
This is why a cassette you used to buy would pretty much always sound better 
than dubbing one off your friend's copy.

Normalizing by itself doesn't create information.  Dynamic range is one analog 
measure of a recording's information content or the ability of your playback 
equipment to reproduce it.

Dave
-- 
Old MacDonald had an agricultural real estate tax abatement.