You cannot preview sound in Effect Options in PowerPoint

When you use the Effect Options to apply a sound to an animation, you cannot preview the sound. The speaker icon in this dialog box only allows you to adjust the volume.

If you want to preview a sound, use the Slide Show Preview or the Play button. To apply a sound to a custom animation and then preview the sound, follow these steps:

1. Click the Custom Animation task pane.
2. In the Custom Animation task pane, double-click the animation that you want to apply a sound to. Or, in the Custom Animation task pane, click the arrow to the right of the animation to which you want to apply sound, and then click Effect Options on the menu that appears.
3. In the Sound list, click the sound that you want to use, and then click OK.
4. If the AutoPreview check box at the bottom of the Custom Animation task pane is selected, the sound will play automatically when you preview the slide animations. To preview the slide animations, click Slide Show at the bottom of the Custom Animation task pane.
5. If the AutoPreview check box is not selected, click the Play button at the bottom of the Custom Animation task pane to preview the sound.