You really can tell how tired someone is by listening to his voice. So says a new study by Australian acousticians Adam Vogel, Janet Fletcher and Paul Maruff in a The Journal of the Acoustical Society of America.
The researchers took 18 healthy adult volunteers (ll male and 7 female) between the ages of 18 and 28, and had them go through a battery of speech exercises every few hours for twenty-four hours straight. The participants were asked to read some text, count from one to 20, tell an amusing or happy story for a minute, sustain vowel sounds and quickly recite the days of the week.
As the subjects grew more tired, their speech patterns changed. In the reading task, for example, pause length increased and speech rate decreased as fatigue set in. The sustained vowel tests demonstrated a decrease in tone variation and an increase in pitch variation with increasing tiredness.
The researchers are hoping to use this information to gauge the tiredness of essential personnel working long shifts. And in case you were feeling sorry for the study participants, they got to spent the intervening hours sitting around watching movies.