The audio will playback faster or slower with clip speed, but only up until a certain point. After that the audio is muted and the waveform is dimmed. You can play up to 3.5 times faster or10 times slower, before it is muted. Outside of that range the audio is unintelligible and is muted.
I believe you can also separate the audio from the video, so for example if you gave a long explanation over one part, which was followed by silence while you waited for something to happen on screen, you could decouple audio+ video, accelerate the video, then overlay the part of the audio you want, and cut out the silent audio.