Texas Fire Chief - Spring/Summer 2008 - (Page 35)

THE FOLLOWING IS AN EXCERPT FROM THE STUDY CONTAINING ITS CONCLUSIONS AND RECOMMENDATIONS: The main conclusions from this study are: 1. Under the testing conditions a 520 Hz square wave T-3 sound was the single most effective signal, awakening 92% of hard of hearing participants when presented at or below 75 dBA for 30 seconds and awakening 100% at 95 dBA. Both the 520 Hz square wave and the 400 Hz square wave were significantly more effective than the 3100 Hz pure tone T-3 sound, which awoke 56% at or below 75 dBA. In addition the 520 Hz square wave signal yielded the lowest hearing threshold when awake for this sample of people who were hard of hearing, from a set of eight alternative sounds with a range of pitch and patterns. 2. Under the testing conditions the bed shaker and pillow shaker devices, presented alone, awoke 8083% of the hard of hearing participants at the intensity level as purchased (vibrating in intermittent pulses). 3. 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. 4. Strobe lights, presented alone, were not an effective means of waking this population, with only 27% waking to the lowest strobe light intensity, which was more intense than that required by the standard (NFPA 72, 2002). 5. There was tentative evidence that people may respond differently to different types of signals, suggesting that a bedroom alarm “kit” that combined two types of sensory signals (i.e. an auditory signal plus a tactile signal) may be more effective than one signal. 6. The results in this study are likely to be overestimations of the proportion of the hard of hearing TEXAS FIRE CHIEF Spring/Summer 2008 population who may awaken to these signals in an unprimed, unscreened population, especially from deep sleep. Thus extrapolations of absolute intensities and percentages awoken in the study to the field should be made with caution. 7. It was found that, when a signal was presented at a level that caused awakening, most people awoke to the signal within the fi rst 10 seconds of the signal being on. Thus it seems highly probable that a T-3 signal that is alternatively ON for about 10-15 seconds and OFF for a certain period of time (possibly of the same duration) will be more effective than a continuous sounding T-3 signal. 8. Questionnaire responses indicated a high level of misplaced complacency among people who are hard of hearing in terms of their need for specialist alerting devices. In view of this, and the fact that many people are not aware of their hearing loss, it is desirable that any standard audible smoke alarm for the general population emit a signal that maximizes the chances of awakening for hard of hearing people (provided such a signal presents no increased risk to other sections of the population). Recommendations: 1. The technical feasibility of replacing the current high frequency smoke alarm T-3 signal with a low frequency square wave T-3 signal (with a fundamental frequency of 520 Hz or thereabouts) for the entire population should be investigated as a matter of priority. 2. A suitable ON duration of such a T-3 signal appears likely to be in the range of 10-15 seconds, with the OFF duration tentatively suggested to be of similar duration but further research is required to determine this. 3. For this population of people with mild to moderately severe hearing loss, the single best emergency alerting device is a low frequency square wave auditory signal. This is superior to bed shakers, pillow shakers and strobe lights presented alone. Ideally this square wave signal should be as loud as possible. There is tentative evidence that combining a low frequency square wave with a tactile device may provide additional waking effectiveness. 4. Any recommendations for the use of strobe lights, presented alone, as an emergency alarm to awaken sleepers who are hard of hearing or of normal hearing should be withdrawn as soon as possible. 5. Further study should be undertaken with people with hearing loss ranging from moderate to profound (i.e. 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 could include strobe lights. In such research it would also be of interest to test bed shakers (vibrating in intermittent pulses) in an under-the-pillow placement. 6. Research on the efficacy of a range of different signals and signal combinations in different populations (e.g. with and without hearing loss) should also be conducted in a large number of home environments where the participants were not primed to expect a signal during the night and unscreened for factors such as medication or prior alcohol consumption. 7. There should be further investigation of an appropriate means of standardizing the measurement of the intensity of bed and pillow shakers and this should inform a new standard. 35

Table of Contents Feed for the Digital Edition of Texas Fire Chief - Spring/Summer 2008

Texas Fire Chief - Spring/Summer 2008 Contents Executive Director’s Report Region Realignment Map Above and Beyond 2007 Conference Highlights ‘Service Above Self’ Texas Commission Implements Southwest Fire Rescue Conference Program Membership Application Who Are Those Guys? Alarms for the Hearing Impaired Recent Calls Index to Advertisers

Texas Fire Chief - Spring/Summer 2008

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