[vorbis] OGG Versus MP3

[Giuliano Pochini]

On 22-Mar-2004 Paul Martin wrote:
>> > IMHO it's a good idea to do so because we're usually not able to
>> > perceive phase differences at higher frequencies.
>>
>> Huh? I've always thought it was the _low_ frequences not sensible to
>> the phase information. Think of 5.1, 2.1, etc systems - they all use
>> that fact.
>
> Phase information at low frequencies is sensed to some extent. It's not
> as pronounced as within the speech band.
>
> Above about 12kHz, the wavelength of the sound in air is less than the
> distance between the ears, so phase discrimination is no longer as
> useful. Relative timings should still be important on impulsive sounds.

And low/very low frequencies have long wavelengths. A sine of 33Hz
is 10 meters long, so the sound that the ears receive is out of phase
of 7 degrees only. Furthermore low frequencies tend to bounce and
resonate easily against the walls of the room. All of this is true
for natural sounds. But a lot of music has artificially out of phase
low frq stuff and the ear if very sensitive to phase information in
the lower part of the spectrum. Also, if you don't save the phase,
you can delete surround information.

<p>
--
Giuliano.
--- >8 ----
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