There's no automated way to ensure that an automated slide show matches the length of an audio track but you can adjust the length of time an image is displayed for (before transitioning to the next one) via the displayTime configuration option (in JuiceboxBuilder-Pro's 'Customize -> AutoPlay' section) and the time it takes for one image to transition to another via the imageTransitionTime option ('Customize -> Main Image').
You should hopefully be able to change the length of time your slideshow plays for with these options.

Here are a couple of tips for anyone looking to do this...

(1) Just in case your slideshow time does not exactly match the length of the audio track, you might like to enable audio looping (so that the audio track starts again after finishing) by setting loopAudio="TRUE" ('Customize -> Audio').

(2) If you want to prevent the user from interrupting the flow of the slideshow (for example, by manual navigation to an image) or pausing the audio track (which would break the synchronization of the AutoPlay and Audio), then you will need to:

• Set AutoPlay and Audio to start on load: autoPlayOnLoad="TRUE", playAudioOnLoad="TRUE"

• Disable keyboard controls: enableKeyboardControls: "FALSE"

• Hide AutoPlay, Audio and navigation buttons from the Button Bar: showAudioButton="FALSE", showAutoPlayButton="FALSE", showImageNav="NEVER", showNavButtons="FALSE" (or just hide the entire Button Bar by setting buttonBarPosition="NONE")

• Prevent thumbnails from being displayed: showThumbsButton="FALSE", showThumbsOnLoad="FALSE"

• Disable image click functionality: imageClickMode="NONE"

Important Note:
Unfortunately, very recently, desktop browsers have started to block the autoplay of audio (and video).
Firefox, from version 66 onwards, now blocks the autoplay of audio (and a click is required from the user to start the audio).
Likewise, recent versions of Chrome, Opera and Safari also now block the autoplay of audio.
playAudioOnLoad continues to work only in Edge and Internet Explorer 11.

Here are the release notes for Firefox 66 where this change of behavior was first noted: https://www.mozilla.org/en-US/firefox/6 … easenotes/

I have contacted the developers to let them know of this and a note regarding this change should be added to our online support documentation in the next website refresh.

Unfortunately, there is nothing that can be done from within Juicebox to override this new browser functionality.
If a user want to allow the autoplay of audio in a browser, then the browser's settings need to be changed by the user.
Please see this web page for more information regarding Chrome, Firefox and Safari.
Chrome: https://developers.google.com/web/updat … cy-changes
Firefox: https://support.mozilla.org/en-US/kb/block-autoplay
Safari: https://webkit.org/blog/7734/auto-play- … for-macos/

As unfortunate as it is, there is nothing that can be done from within Juicebox to force audio to autoplay in modern browsers any more.