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Re: [css3-speech] voice-pitch

From: Daniel Weck <daniel.weck@gmail.com>
Date: Thu, 14 Jul 2011 19:53:09 +0100
Cc: Alan Gresley <alan@css-class.com>, fantasai <fantasai.lists@inkedblade.net>
Message-Id: <545038E2-169F-45BB-AC7F-F60FCDB92D81@gmail.com>
To: www style <www-style@w3.org>
FYI, I sent an email to the Voice Browser mailing list:


Regards, Daniel

On 14 Jul 2011, at 18:12, Daniel Weck wrote:

> On 14 Jul 2011, at 15:57, Alan Gresley wrote:
>> | <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'.
> The formulation can be improved indeed (lifted straight from the SSML specification, by the way).
> The prose is meant to remind readers that the concept of "semitone" in CSS-Speech is the same as the concept of "semitone" in the diatonic scale. And of course, the definition of "semitone" is the same in both the diatonic and chromatic scales.
> Because each and every "step" (interval) on the equal temperament chromatic scale is exactly a semitone, perhaps we should refer to this instead of the diatonic scale. At any rate, we can definitely improve the prose.
>> I also don't understand what the WD means by the part which says 'a semitone doesn't correspond to a fixed frequency'?
> Well, a semitone interval cannot be translated into an equivalent pitch difference without referring to a specific base/starting frequency. In other words, the Hertz value corresponding to a semitone step is defined relatively to an initial pitch, thus why a semitone does not correspond to a "fixed" frequency.
> If you have better wording in mind, please propose! :)
> Many thanks!
> Regards, Dan
Received on Thursday, 14 July 2011 18:53:40 UTC

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