The Logic Off Topic list

--- In logic-ot@y..., "Mark Lennox" <mark@e...> wrote:
> 
> > > I know most people cant hear above say 17kHz or so, and thus the
> argument
> > > for 96kHz sampling rate seems ridiculous.
> 
> j.offerman@i...>;  wrote
> > You are mixing up two *very* different things: 17kHz refers to the
> > highest frequency people can hear, whilst the 96kHz refers to the
> > frequency at which the sound is sampled by digital recorder.
> >
> > I.e. a 96kHz digital recorder samples the frequency of the sound 
that
> > is being recorded 96.000 times per second. This has *nothing* to 
do
> > with the actual frequency range of the sound being recorded.
> 
> sorry Jim, I should have been more specific, I was commenting on 
the fact
> that 44.1kHz recordings can only reproduce tones up to 22.05kHz, 
then I was
> making the comparison that humans can only actually hear up to 20 
odd k
> theoretically (and I made a guesstimate of 17k practically - due 
to  rock
> concerts, traffic, computer whine etc...). Then the fact that the 
higher
> tones cant be heard anyway makes sense, however...
> 
> I made a half-assed guess at beat frequencies generated by high 
order
> harmonics interacting but Lennart pointed out quite rightly that 
such tones
> are produced from perception through a non-linear medium rather than
> superposition in a linear medium (ie. air). Thus to properly 
reproduce these
> beat frequencies you DO need to record as high as you can go.
> 
> The only problem then is how to reproduce these tones. Most titanium
> tweeters I have seen spec sheets for only reproduce up to maybe 30 
or
> 40kHz - how do the higher frequencies get reproduced?

There is a difference between 'reaching' 40kHz and 'reproducing 
correctly' at 40kHz. My Dynaudio tweeters go up to 45kHz +/- 3dB,
 :-). It's not so much those beat frequencies, but more about impulse 
response distortion. Remember that 40kHz is only 1 octave above 20kHz 
and only 2 octaves above 10kHz. The second harmonic of a frequency is 
essential for the human ear; the brain and human 'hearing' experience 
even harmonic distortion as pleasant. Odd harmonic distortion the 
human ear does not like, :-). So the higher the frequency the better.
That's why certain amps have such a high bandwidth. You should know 
that, :-), as a music consultant. And everything in the signal chain 
should be distorted as less as possible.
Yoonchi.