Silencing narration on a main slide

I am personally a fan of the opt-in method of narration.

I provide a button for the learner to click on if they wish to have the slide narrated to them.

Personally, the easiest way to deal with this is to have two versions of that main slide. The first is where learners might see all the animation and hear a full introduction narration. When users click on the "return to main" option to make another selection (my example below was clicking on characters to hear from them), they return to a duplicate version with no animation or narration. Closed captions will work on your initial slide, and it's doubtful your learners will realize they are not returning to the same slide.

To give a more specific answer, I would like to see the Timeline of your 'main slide', because there are indeed multiple workflows possible. Since you are probably talking about slide audio, not any other type of audio, this workflow explained step by step and using micro-navigation may be the most appropriate, but I repeat, depends on the setup of the timeline:

http://blog.lilybiri.com/play-audio-once-on-first-visit

That particular action could also be used to jump over frames which are necessary on the first visit, hence the derived shared action explained in:

http://blog.lilybiri.com/advanced-to-shared-action-step-by-step-micro-navigation-showcase

I keep this shared action, because it can be used in many situations, in an external library to be able to import it directly in any project.

This approach has several advantages:

• You don't need 'two' slides which can mess up other settings and system variables like cpInfoSlideCount
• You can have CC since slide audio is used, which is the problem with other types of audio like 'Play Audio' or object audio.
• If you have effects, staggering of objects on that main slide which you want only to use on first visit, you'll skip over those initial settings as well.

I am assuming that your "main slide" is actually a Menu slide which has buttons or links that enable the user to jump to all the other slides for more information.

There are a number of ways you can achieve the results you describe, and each has advantages and disadvantages.  It's up to you to decide which one is best for your needs.

One solution is just to apply the audio to an object on the main slide instead of the slide itself.  The user will hear the audio when the object enters the timeline.  But if an object is hidden, any audio attached to it will not be heard.  So, the trick here is to use Advanced Actions to hide that object before the learner returns to the main menu slide.  One way to do that is to have the buttons that jump to the other slides execute an advanced action that hides the audio object as well as perform the jump to slide.  That way the object is already hidden by the time they get back. 

The disadvantage of this method is that it doesn't lend itself to use of Closed Captioning because CC text only appears for slide audio, not object audio.  But if you use a shape as the object that plays the audio, then you can make that shape look the same as CC text at the bottom of the slide.  If the text size and background colour of the object and CC are the same, most users would not notice.

If the initial explanatory audio takes up quite a bit of time, another way to achieve a similar result is simply to have two slides that look more or less identical.  The first slide is the one that has the slide audio telling the learner what to do.  The second slide looks the same but is much shorter (e.g. a few seconds) but has no audio.  The trick here is that your learners are returned to the second slide, not the first one.  That way they don't hear the audio.  The advantage of this method is that it doesn't require any advanced actions.  The disadvantage is that you have to make sure learners are not going to inadvertently encounter both slides one after the other.  So you need to make sure the first slide pauses and ensure the learner can only leave that slide if the click one of the buttons.

These are just a couple of ideas for you to try out.