From: zerobeat@intacc.uucp (Ferenc Szabo)
Subject: Re: 8bit vs 16bit?
Date: Fri, 9 Oct 1992 22:02:57 GMT
Organization: Inter/Access' Matrix BBS

In article <718220794.880000.D_NIBBY@UNHH.UNH.EDU> D_NIBBY@UNHH.UNH.EDU (Dana   Nibby) writes:
>
> Can anyone tell me what the difference is in sound quality between 8bit
>and 16bit? I understand about sampling rate, and that if the rate is too low,
>aliasing/clipping occurs. I've asked this question before and gotten no respon.
>  
>  People tend to say, "Well, 16bit sounds better." Gee, well, in what respect?
>Is 8-bit sound tinny, whereas 16-bit sound is warmer? For example, does an
>Ensoniq ESQ-1 sound tinny/weak because it has an 8-bit processor?
>How does 8-bit/16 bit sound compare to what you hear on vinyl? I mean, what
>are the fequency limits of vinyl? And if anything much past 8-bit is useless
>for vinyl... In other words, is 8-bit sound good enough for vinyl records?
>Can a comparison even be made here? Can *someone* out there help me
>understand the difference between 8-bit sound and 16-bit sound? Is 8-bit
>sound 'fuzzy', etc. etc.

Actually, you don't fully understand sampling rate by your above
statement in the first paragraph.  But I'll talk about sampling
resolution (# of bits):

First, a brief binary lesson...... The term 'BIT' is a short 
way of saying 'BInary digiT'.  A binary digit can only have two
'states' or 'amounts'- 1 or 0.  A 1 bit 'word' can therefore only
describe two states.  A 2 bit 'word' can describe four states:
       
                                   00
                                   01
                                   10
                                   11

In other words, there are four different combinations of ones and
zeros if you are talking about 2 digits.

In a 3 bit word, you can have eight different combinations of
ones and zeros. In a 4 bit word you have sixteen different
combinations.  The formula for figuring out the numbers of 
combinations (aka 'the decimal equivalent') is:

                     d=2^b 
      in other words:d=2 to the power of b
    where...    d is the decimal equivalent
                b is the number of bits

so an 8 bit word can represent 256 different states
   a 16 bit word can represent 65,536 different states.

Quite a huge difference between 8 and 16 bit.

______________________________________________________________

So what exactly is digital sampling then?

Digital sampling is representing the analog waveform with a number.
(In a pistachio shell).  An analog waveform is a continous
smooth line (sort of infinite resolution).  To represent such
a waveform perfectly would therefore require an 'infinite bit'
sampler (running at infinite speed too).  But since our
ears can't tell the difference past a certain point, it becomes
feasable (and economically possible) to represent the waveform
with a less than ideal resolution.  16 bits seem to be good
enough for most humans on earth.  8 bits is not simply
'half as good' as 16 because of the of the non-linearity
of the resolution scale.  Remember 16 bits = 65,536 states
and 8 bits = only 256 states.

On your average computer screen, drawing circles and diagonal
lines looks really crappy because of the low resolution.  The
slanted lines exhibit obvious 'stepping'.  This is precisely
what happens to audio at lower sampling rates...you can actually
hear the stepping.  But what does it SOUND like???  8 bit sounds
very grainy with a touch of distortion.  Remember this is
independant of the sampling RATE.  Lower rates aliasing noise.
Aliasing is where the frequencies in the audio that are higher
than half the sampling frequency get folded back mathematically.

If you have a sampling rate of 30Khz, then frequencies over
15 Khz get aliased.  A 16Khz frequency would be folded back
and become 14 Khz, since 16K is 1K ABOVE the maximum it becomes
1K BELOW the maximum.  This effect can be kinda neat for
some things (my SQ80 can do really cool aliasing), but generally
makes things sound crappy because the audio now contains frequencies
that are totally enharmonic.

Well, there are lots of ways to make 8bit sound decent (Emulator II)
and other ways to make a low sample rate sound decent (Roland S50,
S330, S550, W30 all @ 30Khz).  But thats another lesson.

ferenc


Newsgroups: rec.music.synth