Selecting voiceover narration to change playback rate with Javascript?

Hi all,

I am trying to add a feature to our Captivate lessons that allows users to change the playback speed to .75x, 1.5x and 2x. This feature would ideally affect both the speed of the slide and the voiceover, though I would be satisfied if it just affected the speed of the voiceover narration. I have tried following this thread for guidance, but when I try to select all audio on the page, nothing returns:

https://community.adobe.com/t5/captivate/variable-audio-speed-options/td-p/10534223

I combed through the published HTML file to see if I could find how exactly the audio is being played for each slide, but oddly enough I couldn't find any elements for audio. This might be because it's contained within an iFrame? I also tried looking into the Fast Forward function that Captivate has, but it mutes the audio. 

For reference, we don't have computer-generated audio -- we had someone record our script and we put the .mp3 files into the lessons. 

Is there any way to select the audio object so that I can set the playBack property in Javascript? Or are there any other routes I can take to achieve this effect? Thank you for any guidance.