The warning should:
(1) long enough and loud enough to be heard
(2) be distinguishable from other sounds and other warnings (unique)
(3) demand attention
The warning should not:
(1) be annoying due to duration, loudness or other features
(2) be readily ignored due to habituation
(3) be easily missed or misunderstood
(4) have a high rate of false alarms (so it is disregarded)
The device emitting the warning should be:
(1) should be adjustable in sound volume and quality
(2) should be inspected regularly and maintained
(3) cost effective
(4) unaffected by environmental changes
(5) not subject to electromagnetic or other interferences
The warning system should be:
(1) monitored for effectiveness
(2) monitored for need
