[DECtalk] Intelligibility/Listenability criteria

Blake Roberts beroberts at hughes.net
Sun Jul 21 09:46:45 EDT 2019


Don,
For me, whether a speech synthesizer is tolerable or not depends on a few factors.
1. How realistic the voice sounds, naturalness.
2. Whether the synthesizer can handle the amount of text given to it by the screen reading software  without crashing.
3. If I can listen to the synthesizer for a long period without getting ear fatigue.

Let me provide two  examples. Years ago I purchased AT&T voices from nextup.com for use with the the TextAloud program. Since AT&T voices are SAPI5 compatible, I chose to use them with my screen reader. That was a mistake. The voices are so large in size that they would consistently crash after being my JAWS screen reader voice for a minute or two. To me, the AT&T voices I purchased also sound monotone, so I could not tolerate listening to AT&T voices for hours on end in any event. I think there is a newer version of the AT&T voices from Wizard Software which NextUp does not have access to/does not sell. I can only share my perspective based on the voices which I have.

On my Windows 10 system at home, I prefer either Eloquence or Microsoft Mark. When I am using JAWS Professional Edition on my work laptop, I prefer Microsoft Mark or the Vocalizer British English Vocalizer voice Malcolm although I happen to reside in the U.S. Malcolm sounds natural, does not crash and I enjoy listening to him for hours.

These are my thoughts. I know that some people evaluate a synthesizer voice on how fast it can talk. I do not use that criteria myself as an end-user because I prefer slow or medium speed. If a voice is set too fast, I cannot understand it.
Blake
 

----- Original Message -----
From: mattias jonsson <mj at mjw.se>
To: DECtalk <dectalk at bluegrasspals.com>
Sent: Sun, 21 Jul 2019 06:40:35 -0400 (EDT)
Subject: Re: [DECtalk] Intelligibility/Listenability criteria

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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