ANSI/ASA S3.41-1990 (R2008)

Vendor Note: There has been growing interest in the development of an international audible signal which, when heard, would unequivocally mean evacuate the building immediately. Consequently, an international standard, ISO-8201, entitled Audible Emergency Evacuation Signal was approved by ISO and published in December, 1987. This ANSI standard is written to conform with the international standard. In searching for an appropriate audible signal, it was considered that levels of background noise and frequency patterns are so variable, particularly in industry, that no signalling device would be able to penetrate all background noises and frequency patterns. For this reason it seemed prudent to select the kind of sound best able to penetrate audibly a particular background noise pattern in a given building and then to make that sound unique and understandable by imposing on it a standard recognizable pattern of on and off times. Frequently it will be found that whatever sounding device is already in place in the building is there because it has been shown to be successful in penetrating the background noise inside that building. Consequently, all that will be needed in many cases is to impose a standardized temporal pattern on the existing sounding devices. For new buildings a signal should be selected which can penetrate the background noise inside that building and then impose the standardized temporal pattern on that signal. An additional advantage of using a standardized temporal pattern as the distinguishing characteristic of the audible emergency evacuation signal is that the temporal pattern can be applied to visual and tactile signals to aid those who have impaired hearing. Visual and tactile signals incorporating the temporal pattern can also be applied in areas where the background noise is so intense that no signal is capable of penetrating audibly.

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