Run Dolphin in windowed mode. At the bottom you should see a %; this represents the current speed of Dolphin's emulation. Anything less than 100% isn't fullspeed, in which case you may run into audio issues.
You can try the OpenAL backend and increase the Latency until it sounds fine. The audio will slowdown (to a certain extent) if the game slows down.
You can try the OpenAL backend and increase the Latency until it sounds fine. The audio will slowdown (to a certain extent) if the game slows down.