1.6.3 Using sound effects to good effect
Sound effects can communicate information in a variety of ways. In particular, they can do the following.
Reinforce the visual component of the UI. Thus turning a page on the screen could be accompanied by an appropriate sound. This could be taken even further in a children's program about animals, which could include sounds of lions roaring and elephants trumpeting.
Confirm the successful completion of an operation. For example, when my mobile telephone succeeds in connecting to the network, it beeps.
Attract attention. For example, a warning sound might be used to draw the user's attention to an error message displayed on the screen.
As these examples suggest, sound effects usually reinforce other types of output.