Re: [NTLK] Checking in / iPod Comments...

From: Marco Mailand (Newton2k1_at_mac.com)
Date: Tue Oct 30 2001 - 23:24:18 EST


Jon Glass wrote:

> I had a tape deck loose its azimuth
> setting, and one day, while adjusting it, I had a friend tell me that I was
> wasting my time, that it didn't change the way it sounded. ... I'm not sure if he
> just hadn't trained his ear, or was deaf of the ultra high frequencies that
> the adjustment to the azimuth modified. Weird is all I can say.

Indeed. However, adjusting the azimuth simply by listening the treble tones is not all. A small difference might

only be audible if the source sound would provide a means to hear differences in the phases too. That would be a point

source which had to be adjusted to sound from the exact middle.

Or another very simple method which we've used for the azimuth
adjustment at the time of tape recorded computer programs (Z80 based
robotron Z1013 single PCB computer). Our computer club boss recorded on
a high quality stereo cassette recorder white noise with opposite
phases. That was the normal noise on the right channel and the inverted
noise on the left channel. On our monoaural data cassette recorders we
had simply to adjust to minimum noise amplitude and had thus a very
quick and accurate means to have the right azimuth. Since everyone got a
cassette with 2min of this 'special' noise we had a really simple and
cheap tool.

I wonder which differences in hearing could be quantified with
measurements. Large phase differences is probably easy but I assume that
  the adaptive MP3 algorithms might produce amplitude errors which vary
with the dynamic situation of the source.

--
Marco

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