Re: [Harp-L] home recording

[harp <harp@xxxxxxxxx>]

Hi Larry,

These numbers, whether 44, 33, 44.1, 24, etc. all refer to the number of
THOUSANDS of samples taken of an analog audio waveform per second during
the analog-to-digital conversion that takes place in every modern audio
recording and reproducing device.  For example, 44.1 kHz = 44,100 cycles
per second.  Early on in the move from analog to digital recording there
was a LOT of debate about how finely you have to sample analog audio in
order to fool the human psycho-auditory system (the combination of our ear
drums, nerves and what our brain does during the process of sound
perception) into thinking that the diced up step-wise reproduction of a
sound was equivalent to the smooth analog wave produced by nature.  This
guy named Harry Nyquist came up with a rate, now known as the Nyquist Rate
which says, if you want to reproduce a frequency of whatever, then you
have to sample at a frequency of at least two times the original.  When
manufacturers were coming up with the standard for Compact Disks, they
settled on a sampling frequency of 44.1 kHz.  Seems logical - most audio
systems need to pass from some lower frequency, say 20 Hz up to 20 kHz.
Humm - 20 kHz x2 = 40 kHz.  A little extra headroom plus a little fudging
for some of those psycho-auditory characteristics I mentioned earlier and
bingo - 44.1.

What happens if you under-sample, say at 24 kHz?  Short answer is you
start perceiving artifacts.  But unless you are in a quiet room with a
really good system, you probably will never hear it. (Audio purists, feel
free to flame away).

As for 33 kHz, never heard of it, but I have a Zoom, and perhaps for some
reason it is one of the settings - I will have to check.  Frankly, people
who write standards for stuff frequently put in all sorts of corner cases.
 Then the industry settles around some common numbers and people move on.
Don¹t know, but if I was guessing, I would say that is what the deal is
with 33.

Brad

On 12/6/13, 8:16 PM, "Richard Hunter" <turtlehill@xxxxxxxxxxxxx> wrote:

>Larry Sandy wrote:
><Our sound department supervisor recently presented a talk on recording
>and related topics.  He said about 33 bit sampling was <enough and that
>44 bit samples were superfluous.  I'm confused. Maybe he was actually
>discussing another topic.  I understood bit sampling to mean the number
>of digital samples during one cycle on the waveform monitor.  I think
>most in attendance were lost right after his introduction.  Home
>recording is an interesting topic so please keep it going.
>
>Larry, I have never heard of 33-bit and 44-bit sampling.  Most pro audio
>is originally recorded with a bit depth of 24 bits, which is reduced to
>16 bits for commercial CD releases.
>
>I think your sound department supervisor was referring to the sampling
>RATE, i.e. how frequently the audio stream is sampled.  44.1 kHz, 48 kHz,
>or 96 kHz are the industry standards here.  The only device I've ever
>seen with a 33 kHz sampling rate was the Zoom PS-02, which I would not
>describe as a CD-quality recording device. The point is moot, anyway,
>since I doubt that a 33 kHz audio interface is now for sale anywhere in
>the world (unless somebody is blowing out a supply of PS-02s somewhere--I
>sold one a while ago).
>
>Given that there are no audio interfaces out there that work at 33 kHz, I
>have no idea how your sound department supervisor formed his opinion.
>But like I said, it doesn't matter if he's right or wrong, since as a
>practical matter almost nobody reading this will ever see or hear a
>device that records audio at less than a 44.1 kHz sampling rate.
>
>Thanks, Richard Hunter
>
>author, "Jazz Harp" (Oak Publications, NYC)
>Latest mp3s and harmonica blog at http://hunterharp.com
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