Re: Let's build a speakwrite!

From: John Woodgate (jmw_at_jmwa.demon.contraspam.yuk)
Date: 02/26/05 

Date: Sat, 26 Feb 2005 08:49:26 +0000

I read in sci.electronics.design that Rich Grise <richgrise@example.net>
wrote (in <pan.2005.02.26.04.59.18.45961@example.net>) about 'Let's
build a speakwrite!', on Sat, 26 Feb 2005:

>The attention-getter for me was that for a particular phoneme, it made
>absolutely no difference which volunteer spoke the phoneme, the baby was
>responding to the phoneme. The pitch and timbre of the voice didn't make
>any difference - it was the relationship between the formant
>frequencies. Maybe "formant frequencies" is a misnomer

I don't think it is. Look at spectrograms of different vowel sounds.

>- it's more like
>which harmonics are there -

They give timbre.

>but the point is, the spectrum should have
>the same _shape_ for a given phoneme, when you bandpass filter it to,
>say, 300 Hz - 3 KHz, which, according to the 1963 Radio Amateur's
>Handbook, is where all of the information in voice is anyway.

It isn't. 300Hz is perhaps OK, although some male formats go down much
lower; the ear/brain regenerates the fundamental pitch from the
harmonics. But 3 kHz is only OK for vowels. You can't distinguish 'f'
from 'th' with only 3 kHz upper band limit. Consonants are most
important for intelligibility, and their spectra go up to 8 kHz at
least, although you can usually get by with a 6.3 kHz upper band limit. 

-- 
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk