[DECtalk] Intelligibility/Listenability criteria

[mattias jonsson]

my favorite voices: vocalizer swedish alva for swedish,vocalizer evan us english


Den 21 juli 2019 10:18:11 skrev Damien Garwood <damien at daygar.plus.com>:

> Hi Don,
> Here are my criteria:
>
> 1. Understandability
> As a screen reader user who has to listen to speech synthesis on a 
> constant basis while using a computer, understandability is first and 
> foremost. If the synthesiser can't be understood, then you're not going 
> to get the feedback you need. In my opinion, ESpeak ticks every box, 
> except this, so I can't use it.
> 2. Responsiveness. Again, because the speech is reading everything for 
> me, I don't want a synthesiser that acts sluggishly with any kind of 
> latency, whether that be a second, or 50 milliseconds, whether through 
> lack of performance optimisation or through audio silence. When I press 
> a key, I want instant feedback. This automatically rules out most 
> natural-sounding synthesisers.
> 3. Accuracy: It needs to be able to read text accurately for the 
> language it is designed for. It's not enough simply to have a phonetics 
> dictionary, but it also needs to be able to distinguish between words 
> (Present noun versus present verb, for instance).
> 4. Flexibility: The voice timbres should be available to the user, and 
> for the most part should adjust smoothly to the change. This is 
> important if a user has specialist needs and cannot use the synth in its 
> default state. Speed and pitch are definitely a must. Again, this rules 
> out natural synths, since due to the nature of recorded samples they 
> start to begin to sound unnatural if you attempt to adjust the speed and 
> pitch. The bigger the change, the more unnatural.
> Like Jason, I also prefer formant synths. My favourite by far is 
> Keynote, which to me is the most understandable, but I do love DECTalk 
> for its flexibility. I also like Eloquence and the synthetic version of 
> Orpheus.
> Cheers,
> Damien.
>
> On 21/07/2019 05:53 am, Don wrote:
>> Hi,
>> 
>> Perhaps a bit off-topic for this list... if so, my apologies.
>> 
>> I'm looking for opinions as to how one evaluates the "effectiveness"
>> of a particular synthesizer.  Said another way, how one decides that
>> synthesizer A is "better" than synthesizer B.  Ideally, criteria that
>> would allow you to rank a set of them!
>> 
>> I've been auditioning various synthesis devices and techniques
>> to try to come to my own conclusions on this.  Then, hopefully,
>> work backwards to come up with some objective criteria by which
>> they could each be "scored" (even if that was done using bogus
>> rating units).
>> 
>> "Intelligibility" is, of course, the prime issue.  "Listenability"
>> coming into play for any prolonged use.  Finally, "naturalness"
>> when it comes to extended use.
>> 
>> For example, the old Votrax units were intelligible -- once you
>> learned their "accent".  But, listenability was rather poor... you
>> quickly developed ear fatigue.  And, the idea of naturalness was
>> never even considered!
>> 
>> With gobs of resources (hardware, software, processing power), you
>> can achieve quite acceptable results.  This seems to be the approach
>> most "modern" synthesizers -- and techniques -- adopt.  The real problem
>> lies with limited resources attempting to handle unconstrained input.
>> (If you know what you're going to be asked to speak, it's really easy to
>> come up with a good presentation!)
>> 
>> Limiting the user's exposure to the synthetic voice can reduce ear fatigue.
>> So, dealing with it for 10 minutes might be tolerable while 2 hours
>> would be torture.
>> 
>> But, having to face the prospect of completely unconstrained input can
>> tax even that brief usage.  "Dr. Jones' car -- bearing the license plate
>> FTDKTR -- has been parked in front of his house on Jones Dr. since 12:34A
>> this morning when his Polish butler finished polishing it."  Imagine you
>> have no other way of inspecting the input text...
>> 
>> So, what makes a synthesizer "tolerable" or "intolerable"?  What is the
>> "threshold of pain" when it comes to tolerating an underperforming
>> synthesizer?
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