control image visibility

I currently have the "Next" button configured to appear when the audio finishes by setting the "transition in" to the length of the audio clip. But if the student goes back to the page, I don't want him to have to wait for the audio finishes again before he can move on. How do I fix it so that the "Next" button transitions in after the audio only the first time the slide is shown?

Thanks in advance for your help.

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