Sound
An application should not convey important information by sound alone, because some users will not be able to hear or recognize it. The user may be deaf or hard-of-hearing or may simply be using the computer in a very noisy environment, such as a workshop, or in a very quiet environment where it is inappropriate for the computer to be making sounds.
Applications make sounds for a variety of reasons. There are four different types of sound:
- Important sounds, which convey information that is not presented visually and which is important to the operation of the application. Examples include an audio wave file with narrative instructions or a sound notifying the user that new mail has arrived.
- Redundant alerts, which accompany a visual presentation of information, yet serve an additional purpose of attracting the attention of a user who is not looking directly at the computer screen. An example is the optional beep that can accompany a message box.
- Redundant sounds, which repeat information already presented visually and are not required for proper operation of the application. An example is an error sound or beep that is heard when the user tries to move beyond the end of a list box.
- Decorative sounds, which enhance the appearance or presentation of an application, but are not required for its operation. Examples include the sound effects that accompany minimizing a window or activating a menu and background sounds and music used to establish a mood in many multimedia games.
The user who cannot hear redundant or decorative sounds is not disadvantaged, but the first two types of sound, important sounds and redundant alerts, do require special attention.
For redundant alerts, Windows 95 and other utilities have the capability to detect when the computer is making noise and to display a generic visual indicator to the user. This feature is referred to as "SoundSentry." This feature works reasonably well in cases where the sound is just a generic beep that is warning the user or trying to attract his or her attention. However, it is of limited use with applications that use different sounds to convey more complex information.
Conveying important sounds and complex information requires the cooperation of the application.