Sound intensity required for waking up

The response of sleeping subjects to sound stimuli whose intensity increases with time is analysed, using a random walk model with varying upper boundary developed in a previous paper. The data came from an experiment carried out by Ball and Bruck to compare the response time of sleeping subjects to three different auditory stimuli. The sound intensity increased steadily with time and the young adult subjects (seven males and seven females) were tested when sober and with blood alcohol levels of 0.05 and 0.08. The analysis revealed that alcohol had a very significant effect in slowing down the response of all subjects. It also revealed that sober females responded at lower sound intensities than sober males and were less affected by alcohol than males at the same blood alcohol concentration. The great advantage of using the random walk model is that it allowed the estimation of the high percentiles of the probability distribution of the sound intensity required for waking up, for each combination of gender, type of auditory stimulus and alcohol level. It also allowed the estimation of the proportion of subjects in each category that would not wake up at the maximum realisable sound intensity of 95 dbA. The analysis underscores the severity of the danger of not being sober or even low alcohol consumption for sleeping subjects in a fire and points to possible improvements in the type of sound used in fire alarms.