Adding Audio Controls

Hello! I'm new to Storyline so forgive me if this question is really elementary. I'm designing a module on building accessibility into e-learning material so I've created audio narration for all of my slides. However, I know that not all learners want to listen to the narration so I've also added some user controls. 

On the slide master, I've added a audio on and audio off button which actually changes the state of the PlayAudio variable. When a new slide is presented, the audio will play/not play depending on what the user selected (default is to play audio). Since the audio buttons are on the master, the user can change their mind on any slide by selecting/deselecting the audio option (which will change the state of the variable). HOWEVER, the change is manifest when the module advances to the next slide.

My question (sorry about the long intro) is how I can keep the user-choice functionality (that changes the PlayAudio variable for the entire module) but also provide the learners an opportunity to play/stop the media immediately without having to wait until the next slide to see the changes? Some of my users are complaining that they like the audio buttons but say they don't work. They do work...you just don't see the effect until the module advances.

Does that make sense? Is there a better way to do this?