displays are most often used to attract and direct a user's attention.
Typically, auditory displays convey caution, warning, or danger
information. Auditory displays can be powerful "attention getters,"
depending on the characteristics of the sound used and the surrounding
environment. Examples are fire alarms, burglar alarms, ambulance,
and police sirens. For these applications, auditory displays are
preferred because they need not be in the field of view to be used.
Generally, sound should be accompanied with visual indicators such
as flashing or strobing red lights for redundant sensory coding.
When designing auditory displays, loud (high decibel level) alarms
should be reserved for life-threatening, critical events and lower
levels used for less threatening alerts. Care must be taken in the
selection of tones, decibel levels, and alarm/alert rates. While
a powerful "attention getter," sound can also be a "task
interrupter" and nuisance. For this reason, it should be sparingly
smoke detector uses an auditory display. Placed appropriately,
it can warn inhabitants anywhere in a building or home of danger
before the sight of fire or smell of smoke becomes apparent.