Subject: Re: Frequency response was Re: [linux-audio-user] Audiophile CD's
From: Paul Winkler (pw_lists_AT_slinkp.com)
Date: Mon Jan 28 2002 - 19:49:01 EET
On Mon, Jan 28, 2002 at 03:16:04AM -0500, Jason wrote:
> True, but I'm not convinced that that necessarily means that everything we
> hear is heard that way because our brains are constantly summing a bunch
> of sine waves.
That's actually surprisingly close to how it works, IIRC. The ear is
sort of like a massive parallel bank of very narrow-band filters
feeding amplitude sensors. FFT, in other words.
> However, I can tell the difference between a 16k sine wave and a 16k
> square wave, and I can honestly say that the 16k square wave sounds like a
> square wave, and not simply "different" from the sine wave- It's a pretty
> easy test to execute, I suggest everyone
> interested sampling frequencies conduct it at several different sampling
> rates, it was a bit of a revelation for me- Which means
> that either a.) you can hear much higher frequencies than 20kHz, and your
> brain simply ignores them when they aren't associated with a lower
> fundamental frequency (frankly, that seems a bit unlikely) or b.) The
> brain doesn't process timbre by performing lightning quick FFT on the
> input
> from the audio nerves.
Well, this is very interesting because b) contradicts everything I've
read about how hearing works. I would very much like to experience
this for myself, it would change my understanding quite a lot. So I'd
like to ask you a bit about how you executed this test.
* Did you do a blind test? i.e. was there any way for you to know
which signals were which?
* How did you generate and play back the 16 kHz square wave? Did you
use an analog tone generator, or a digital system with extended
response? If digital, what did you use to generate the test signal,
and what did you do about aliasing?
* Do you know for sure that the playback system doesn't produce
distortion below 20 kHz when faced with harmonic content at 32 kHz and
above? How can this be verified? I don't know how to do this on my own
system...
--paul winkler home: http://www.slinkp.com music: http://www.reacharms.com calendars: http://www.calendargalaxy.com
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