In PowerPoint 2013, on the Playback tab, just choose Play Across Slides (and skip the next steps). In 2007, go to Animations tab> Custom Animations in 2010, on the Animations tab, click Animation Pane. The Custom Animation pane opens with your sound file listed.
In PowerPoint 20, you need to click the Audio Tools Playback tab and choose Automatically from the Start drop-down list. (You see a sound icon, which you can drag off the slide if you don’t want it to appear during your presentation.)
In PowerPoint 2007 – 2013, go to Insert tab> Media Clips group> Sound/Audio. In PowerPoint 2003, choose Insert, Movies and Sounds, then choose one of the options, such as Sound From File.
