AbstractThis paper assesses the waking effectiveness of strobe lights and pillow and bed shakers as smoke alarm warning devices and compares them to an auditory signal. The signals were activated at increasing intensity levels during slow wave (deep) sleep in two groups, (i) 38 adults aged 18-77 years with hearing loss of 25-70 dBA in both ears, and (ii) 32 young adults aged 18 -26 years impaired with alcohol at 0.05 blood alcohol content. Three quarters of both groups slept through the strobe light activated at above the intensity required by the standard whereas a 75 dBA 520 Hz square wave T-3 sound woke over 90%, and at a louder volume 100%. The pillow and bed shakers did not wake 17-20% of the hard of hearing participants at the intensity level as purchased. Hard of hearing participants aged ≥60 years were less likely to wake up to the bed shaker than those aged <60 years. The pillow and bed shakers tested were not an effective means of waking moderately alcohol impaired young adults from deep sleep, with 36%-42% not waking up at the intensity level as purchased. For both groups the pillow and bed shakers were less effective than the 520 Hz square wave T-3 sound at 75 dBA at the pillow. This study supports earlier research showing that when sleep stage is assessed strobe lights have poor waking effectiveness. The 520 Hz square wave sound was more effective than the non-auditory signals for both groups.
Conclusion
Strobe lights, presented alone, were not an effective means of waking either of the two population groups tested. Under the testing conditions three quarters of the people in the hard of hearing and alcohol impaired groups did not wake up to the lowest strobe light intensity, which was more intense than that required by NFPA 72. Thus it is not appropriate to recommend strobe lights, either alone or in tandem with the current high pitched smoke alarm, as an effective means of waking people whose hearing loss is less than moderately severe (i.e. hearing thresholds of less than 70 dBA) or who have even a low (0.05) blood alcohol level.
Under the testing conditions the pillow and bed shakers, presented alone, did not wake 17-20% of the hard of hearing participants at the intensity level as purchased (vibrating in intermittent pulses) and those hard of hearing participants who were aged 60 years or more were less likely to awaken to the bed shaker than those aged below 60 years. No age group differences were found for any other signal. The pillow and bed shakers tested were not an effective means of waking moderately alcohol impaired young adults from deep
sleep, either at the intensity level as purchased, or at higher intensity levels. At the intensity level as purchased 36%-42% did not wake up.
These studies add to previous research suggesting a low frequency square wave (with a fundamental frequency of 520 Hz or thereabouts) is the most effective alerting signal tested to date and would be an appropriate emergency alerting device for those with hearing loss within the range tested in this study. Further study should be undertaken with people with higher levels of hearing loss (including deaf people) to determine the best signals, or combination of signals, that will reliably awaken this population from deep sleep. This should include bed shakers, pillow shakers, low frequency square waves (beneficial for those with residual hearing) and perhaps could include strobe lights.
