High and low notes

Fire studies examine alarm signals for at-risk groups
SSN Staff  - 
Saturday, September 1, 2007

QUINCY, Mass.--Two studies released July 26 appear to indicate that an alarm signal with a mix of high and low frequencies is the most effective in waking high-risk groups such as alcohol-impaired young adults and individuals with mild-to-moderate hearing losses.
The Fire Protection Research Foundation, an affiliate of the National Fire Protection Association, conducted the studies.
What might the implications of these studies be for manufacturers and installers of fire systems?
In an email interview, Kathleen H. Almand, executive director of the The Fire Protection Research Foundation, noted that most fire alarms today have a single high frequency sound, and said, "Manufacturers may use this information in the design of the next generation of alarms which may include new types of alarms incorporating these frequencies or developing systems which provide a louder sound or an alarm system which sounds throughout the house (which would then be louder at any given location)."
Alcohol impairment among young and middle-aged adults is a key factor in more than half of U.S. fire fatalities, according to the NFPA."Waking Effectiveness of Alarms for the Alcohol Impaired" examined the effect of alcohol consumption on the ability of 32 young adults, aged 18 to 26, to awaken to several auditory and alternative signaling devices. Two lower frequency alarm sounds (400 Hz and 520 Hz) were significantly more effective in waking participants than the higher frequency alarm sound (3150 Hz) used in most smoke alarms, the NFPA reported.
"Waking Effectiveness of Alarms for Adults who are Hard of Hearing," showed that auditory alarms--as opposed to alarm methods such as bed shakers, pillow shakers and strobe lights--are most effective for waking this demographic group.
It also found that "the standard audible emergency evacuation signal (a repeating pattern of three tones and a pause) with a lower pitch tone (520 Hz)" awakened significantly more participants than the higher pitched tone (3150 Hz) used in most alarms.