People likely to commit suicide have a distinctive tone of voice
A subtle change in the sound of someone's voice is the first sign that they are serious about committing suicide. The change is so distinctive that psychiatrists plan to use the sound change as an early warning system to separate those who are seriously suicidal from those who are merely depressed.
The idea that the voice might contain vital clues about someone's mental health came when Stephen Silverman, a psychiatrist at Yale University, noticed he could often sense from a patient's voice whether they were likely to attempt suicide in the near future.
To find out if this observation had any practical use, Silverman teamed up with Mitchell Wilkes, an electronics engineer based at Vanderbilt University in Nashville, Tennessee.
Wilkes recorded a series of interviews with 64 depressed patients and compared them with recordings of 33 others who weren't depressed. In total, 22 patients made a serious attempt on their lives.
He then compared the recordings with the subsequent history of the patients. "In suicidal patients, the voice becomes slightly hollow and empty, you get this change in quality," he says. "They call it the voice from the grave."
Wilkes found that two factors helped him discriminate between those who were at high risk of committing suicide and those at low risk. First he noticed that people who are truly suicidal use a narrower range of frequencies when pronouncing their vowels than people who are just depressed. The voices of suicidal people also become higher pitched. "We find there's a noticeable difference between suicidal and normal, and normal and depressed people," he says.