Frequency/Sample rate

Most audio files on the net are recorded at a 44 KHz sampling rate,
but it's mainly referred as "frequency." Now, humans can only hear up
to 20 KHz, so why would audio be recorded at 44 KHz (twice the audible
hearing range?) , one can notice the difference if the song
was downsampled to 22, so why not coin the standard frequency at 22
KHz instead of 44, why is the number doubled? Also, just where the
hell did the number 44,100 emerge from? Why not 40,000?

Nowadays, DVD-audio songs are recorded at 96/192 KHz, is there a
point?

And if this ain't the case, why would the sampling rate be called
"frequency?"

Industrial wrote:
) Do I understand correct: hz is one sine loop per second,

Hz is one <whateverper second.
Your heart beats at roughly 80 Hz.
The moon revolves around the earth at roughly 0.38 uHz (Microhertz)

) I generate a
) sine sweep from 0 - 20 KHz with a specified duration, when I view with
) an audio application and zoom 'till individual samples are visible, I
) notice that as frequency increases, the sine waves become shorter, and
) gradually begin to appear more triangular as the smaller sample
) interval makes a perfect, smooth sine shape impossible. Finally, when
) it reaches 20 KHz (20,000 sampling rate) the waves have reached their
) limit on appearing anything that resembles a sine, and is now a
) perfect triangle: one sample at the bottom, one at the top, and one at
) the bottom again, like /\/\/\/\/\/\/\/\/\/\. This would technically be
) the maximum, but instead, as I continue scrolling, I see the waveform
) look something like a private-case of sine waves. This time, a sine
) block composed of triangles. What you're saying is that beyond 22.05
) is a hack that simulates higher frequencies, but don't technically
) exist on a digital medium, like the waveform of the sine sweep I
) created?

Play your sample at half speed and listen to what happens when
you reach 11.025 Khz.

), one can notice the difference if the song was
)downsampled to 22,
)>
)You notice it because reducing the sampling rate to 22KHz
)actually reduces the top end to 11KHz which many people
)can detect.
)
) I don't follow. Why 11?

Because 11 is half of 22. See above.


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something
No I'm not paranoid. You all think I'm paranoid, don't you !
#ET

Earl Kiosterud wrote:
I notice that Audacity displays sample points connected with straight
lines. I don't think that's meaningful. editors show what a
post-filter, presumably at 20 KHz, would show, along with the sample
points.


That would be very presumptive of editing software. SForge shows
straight lines between samples - I would be most peeved if SF made an
arbitrary decision about a filter.

geoff

Arny Krueger wrote:
>
Phase linear response does not give sufficient audible advantages to
offset the difficulty of building loudspeakers that have it.

I want a phase-linear room.

geoff

"ChrisCoaster" wrote
Very simple. CDs have two channels of sound: Left, Right, A, B, 1, 2,
whatever you want to call them. L22kHz + R22kHz = 44kHz.

Absolutely not. Each channel is sampled at 44.1KHz.
There is no "L22KHz + R22KHz = 44KHz".

ChrisCoaster wrote:
) The audio CD sample rate is set at 44,000Hz(44kHz) for a simple
) reason: Two channels - Left, Right, A,B, whatever you want to call
) them. Each channel gets up to 22kHz.

Where/who did you get that ridiculous idea from ?


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something
No I'm not paranoid. You all think I'm paranoid, don't you !
#ET

ChrisCoaster wrote:
) Topic: If someone can explain the 44.x sampling rate of CDs to
) someone whose math skills are limited to adding/subracting whole
) numbers, it would be appreciated. My idea that 44kHZ was space enough
) to contain 22kHZ for two stereo channels was obviously wrong, and
) something I would like clarified/corrected after having believed it
) for 20 years now.

Easy:

If you have a sound with a frequency of 20kHz, that means that the wave has
to go through one complete cycle 20.000 times a second. That is: up *and*
down 20.000 times a second. To record that you need to record both the ups
and the downs, so that's 20.000 ups plus 20.000 downs, makes 40.000 samples
per second.

Why they went up from 40kHz to 44.1kHz is some weird technical reason,
explained in another part of this thread.


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something
No I'm not paranoid. You all think I'm paranoid, don't you !
#ET

Willem wrote:
ChrisCoaster wrote:
) Topic: If someone can explain the 44.x sampling rate of CDs to
) someone whose math skills are limited to adding/subracting whole
) numbers, it would be appreciated. My idea that 44kHZ was space
enough ) to contain 22kHZ for two stereo channels was obviously
wrong, and ) something I would like clarified/corrected after having
believed it ) for 20 years now.
>
Easy:
>
If you have a sound with a frequency of 20kHz, that means that the
wave has to go through one complete cycle 20.000 times a second.
That is: up *and* down 20.000 times a second. To record that you
need to record both the ups and the downs, so that's 20.000 ups plus
20.000 downs, makes 40.000 samples per second.
>
Why they went up from 40kHz to 44.1kHz is some weird technical reason,
explained in another part of this thread.

You are, I hope, joking. Cos that is total crap.

geoff

ChrisCoaster wrote:
If you have a sound with a frequency of 20kHz, that means that the
wave has to go through one complete cycle 20.000 times a second.
That is: up *and* down 20.000 times a second. To record that you
need to record both the ups and the downs, so that's 20.000 ups plus
20.000 downs, makes 40.000 samples per second.
>>
Why they went up from 40kHz to 44.1kHz is some weird technical
reason, explained in another part of this thread.
>>
>You are, I hope, joking. Cos that is total crap.
>>
>geoff- Hide quoted text -
>>
>- Show quoted text -

Alrighty geoff, then YU explain it. And remember, easy on the math!
>
'Cause at this point I'm about hit "Wiki" in my favorites.
-CC

Simple. To accurately recontruct a waveform, you need two samples of the
highest frequency specificied. Look up Nyquist Theory on you beloved Wiki -
even Wiki has that right !

Nothing to do with 20KHz worth or 'up' and 20KHz worth of 'down'.

geoff

Jul 15, 4:22*am, "Mr.T" <MrT@homewrote:
. My only point was
that *I think* 500dB or 1000dB SPL is still *theoretically* impossible in
air.
>
MrT.- Hide quoted text -
>
- Show quoted text -

Ask anyone who has been within 5-miles of a 1950s atomic bomb test.

-CC