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Re: [css3-speech] voice-pitch

From: Alan Gresley <alan@css-class.com>
Date: Fri, 15 Jul 2011 00:57:52 +1000
Message-ID: <4E1F03F0.2060306@css-class.com>
To: Daniel Weck <daniel.weck@gmail.com>
CC: www style <www-style@w3.org>, fantasai <fantasai.lists@inkedblade.net>
On 14/07/2011 3:26 AM, Daniel Weck wrote:
> On 13 Jul 2011, at 17:56, Daniel Weck wrote:
>> Okay, let me publish an update to the pitch properties, where the
>> CSS notation is aligned with SSML's calculation method. I will then
>> ask the CSS syntax / parsing gurus to review the correctness of the
>> prose. :)
> Could you please review the updated prose:
> http://dev.w3.org/csswg/css3-speech/#voice-props-voice-pitch
> The pitch-range definition of percentages is identical:
> http://dev.w3.org/csswg/css3-speech/#voice-props-voice-pitch-range
> Thank you very much! Daniel

In regards to the semitone value.

   | <semitones>

   | Specifies a relative change (decrement or increment)
   | to the inherited value. The syntax of allowed values
   | is a <number> followed immediately by "st" (semitones).
   | A semitone is half of a tone (a half step) on the
   | standard diatonic scale. As such, a semitone doesn't
   | correspond to a fixed frequency: the ratio between
   | two consecutive frequencies separated by exactly one
   | semitone is the twelfth root of two
   | (approximately 1.05946).

The above does not quite sound correct. Part of what the WD says above 
concerning the 'twelfth root of two' [1] is actually the ratio scaling 
of the 'chromatic scale' [2] with has all steps a semitone apart and an 
even ratio increase/decrease in hertz. The 'diatonic scale' does not 
have this even scaling and it only has seven steps 'T-T-S-T-T-T-S'.

I also don't understand what the WD means by the part which says 'a 
semitone doesn't correspond to a fixed frequency'?

[1] http://en.wikipedia.org/wiki/Twelfth_root_of_two
[2] http://en.wikipedia.org/wiki/Chromatic_scale
[3] http://en.wikipedia.org/wiki/Diatonic_scale

Alan Gresley
Received on Thursday, 14 July 2011 14:58:24 UTC

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