Audio wavelength disappears when creating a trigger

I have inserted a .wav audio in my Storyline project. As usual, I can see its duration (wavelength) on the timeline. However, when I create a trigger on the corresponding audio icon (play media when user clicks), the wavelength disappears and is replaced by a speaker icon. This prevents me from seeing the duration and syncing it with the rest of the items on the slide. What can I do? 

Edit: This is in relation to an exercise where students here an audio that I place at some point in the timeline (maybe at the very beginning) and then I leave an audio icon so that they can listen to it again.

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