Bug #9515


Text to Speech plugin - "More Slowly" checkbox not working

Added by scott voth over 6 years ago. Updated about 6 years ago.

Reporter Feedback
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WordPress Plugins
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Hi Ray - Thanks for activating. Samuel is reporting that the checkbox "More Slowly" is not slowing down the speech when he checks it. Can you take a look? Site is

We had to deactivate one plugin (media element html5) to get some pages to show the change - maybe another plugin is causing troubles? The checkbox is in the footer of each page.

here is a link to the original request -

Actions #1

Updated by Raymond Hoh over 6 years ago

  • Target version set to Not tracked

Hi Scott,

I tested the "More Slowly" checkbox and it is working for me in Firefox, Chrome, Edge and IE11.

Does Samuel have any other steps to duplicate the bug? Also what browser is he testing with?

Actions #2

Updated by scott voth over 6 years ago

Hi Ray - I think he is using Chrome, but I can ask. But even for me, it does not seem to work on a Mac. (I've tried Firefox and Chrome.) I went to my wife's PC and there - success - it is definitely working. But on my Mac, I cleared cache - but it doesn't seem to slow down.

Actions #3

Updated by Raymond Hoh over 6 years ago

Hi Scott,

I don't have a Mac, so it's hard for me to debug the issue. Is Samuel also experiencing the problem on a Mac?

Did your custom plugin work on a Mac before we added to the Commons?

Actions #4

Updated by scott voth over 6 years ago

Yes, it was working on a Mac when I made the changes. I believe Samuel is using a Mac too, but I will ask him and get back to you.

Actions #5

Updated by scott voth over 6 years ago

  • Assignee changed from Raymond Hoh to Boone Gorges

Thanks Ray - It is hard to debug if it is working on Windows and you don't have a Mac

Boone - can you take a look?

Actions #6

Updated by Boone Gorges over 6 years ago

  • Status changed from New to Reporter Feedback

The issue seems to be that the RseponsiveVoice.js library uses the SpeechSynthesisUtterance API when the browser makes it available. In the case of certain Apple platforms, the API is there, so ResponsiveVoice.js uses it. But the library appears to be written in such a way that the `rate` option works only when the non-SpeechSynthesisUtterance fallback is used.

It's difficult for me to debug this further, because the ResponsiveVoice.js library is minimized, and they don't provide an uglified version in the plugin or on their website. I'd suggest that the user open a request with the vendor so that their team can have a look at it.

Actions #7

Updated by scott voth about 6 years ago

Hi - I finally got a reply from responsiveVoice team:

We have recently added a few more parameters such as rate, pitch and volume. You can adjust them with

[responsivevoice_button rate="1" pitch="1.2" volume="0.8"]

The development team has also provided us with a link to the non-minified version of ResponsiveVoice.js (here: but you might find that not all voices allow for rate/pitch changes, and we unfortunately cannot share how our backend works for fallback.

Hope this helps!

Kind regards,
ResponsiveVoice Support



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