[vorbis-dev] Psycho-acoustics research

[Segher Boessenkool]

> My idea so far is to record several speakers producing minimal pairs
> (such as 'zip' and 'sip') and to compress the sound under different

Those are not minimal combinations; minimal combinations are
"two letter" sounds, like "zi" and "ip".

> compression schemes (Ogg, MP3, GSM, etc) at varying levels of
> compression, then play them back on decent audio equipment for
> listening tests to see if listeners can still distinguish important
> parts of the sounds in the recordings. In particular, I'm interested
> in looking at the nature of degradation when the compression ratio is
> particularly high: what phonemes become more difficult to distinguish
> soonest, as the compression ratio goes up?  And then, if possible, I'd
> like to come up with an analysis of *why* those particular sounds are
> poorly recreated, as opposed to others.  My guess is that fricative
> sounds (/f/, /v/, /s/, /z/) will "degrade" first because they contain
> larger amounts of white noise, which is often poorly handled by
> compression.

In my experience, Vorbis is worst with plosive sounds.  But different
codecs have their own problems.  And it varies with listener, too.

> A couple other people in my classes are interested in working with me
> on the project - one has more math background, one is willing to
> administer perception tests on a group of people.  I have the

Group of people is a good idea.

> linguistics background.  We have until the end of April to do the
> project, and the exact idea should be decided on by the end of this
> week.
> 
> I'd like to know if there's something I could do that would be more
> helpful than academic. So... got any ideas for a project within this
> scope that would directly benefit Ogg Vorbis development? Changing
> topics is possible, though it would be preferable for it to have a
> strong linguistic element so I can use the project for both classes.

Vorbis is not a speech codec, so this won't directly help Vorbis.
But it might certainly be helpful by giving further insights in what
we do and don't do well, right now.

Good luck with your research, and have fun!

<p>Segher

<p>--- >8 ----
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