This comes up all the time in the Mission Scripting forums. The issue is that Artemis is designed to play monophonic audio files, but by default Audacity saves stereophonic audio files. Artemis plays stereo files at half speed.
Re-save your audio as mono and it will sound right.
"Damn the torpedoes! Four bells, Captain Drayton!"
(Likely actual words of Admiral David Farragut, USN, at the battle of Mobile Bay. Four bells was the signal for the engine room to make full steam ahead).