Intelligibility of Long-Distance Emergency Calling.

OBJECTIVE This study examined the identification of emergency calling across distance without electronic assistance, as in the event of an electric grid black-out or being stranded in the wilderness. METHODS Fifteen participants were callers and forty-one participants were recorders. Ten callers underwent an hour-long training in how to produce vocally healthy loud phonation, as well as, yodeled calls. Outdoors, the callers individually called out a set of single and multisyllable words, either yodeled or nonyodeled. Recorders and sound level meters were placed at four distances from the caller and were asked to select the called word as part of a closed-set identification task. RESULTS Distances greater than 100 m had significantly reduced call identification. Caller sex did not yield statistically significant differences in call identification at any distance. Participation in training only yielded a statistically significant difference in call identification at 170 m. For distances greater than 25 m, multisyllabic words were significantly better identified than single syllable words. Nonyodeled calls had a higher score by a statistically significant amount for ranges above 50 m than yodeled calls. Yodeled calls were found to have a greater sound level than nonyodeled calls at greater distances. The study results were consistent with the inverse square law. CONCLUSIONS Even a small amount of training can provide improvement in identification at long distances. Multisyllable words provide better identification than single syllable identification at distances beyond 25 m. Future research is recommended, focusing particularly on the amount of training necessary to improve identification and environmental effects on identification.