Sound effects can be effective if applied wisely to PowerPoint slide transitions. For example -- a presentation that is about the increasing sales figures might be effective with a cash register sound effect on a slide transition.
There is also an option to Loop Until Next Sound which you can apply to the slide transition. In my opinion, this should be used only sparingly, and only in certain situations (such as a presentation for small children). The sound effect will keep repeating until another sound effect is reached, and could be very distracting to the audience. A single sound effect will certainly make your point.
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