Researchers at the Vanderbilt University in Tennessee, US, found that the voices of people who are suicidal become higher pitched.
The researchers also discovered that they use a narrower range of frequencies when pronouncing their vowels than people who are just depressed.
According to Mitchell Wilkes, an engineer at the university and one of the authors of the study, the reason for the voice changes may be stress-related.
"We find there's a noticeable difference between suicidal and normal, and normal and depressed people.
"In suicidal patients, the voice becomes slightly hollow and empty. You get this change in quality. They call it the voice from the grave."
He added: "A variety of changes can take place under stress - like muscle tone quality - that can affect the vocal chords.
"Also, you get changes in moisture and elasticity of the vocal tract."
The researchers carried out a series of interviews with 64 depressed patients and compared them with recordings of 33 others who were not depressed.
Of these, 22 patients made a serious attempt on their lives.
The researchers believe that the findings could help doctors and helpline operators to identify those people at risk of committing suicide.
"The goal is to have a diagnostic device for emergency rooms or that could be linked up to helplines," said Mr Wilkes.
"It could help volunteers on those phones answer the question: is this person in danger of committing suicide?"
The Samaritans in the UK welcomed the research. Emma Charvet, who works with the organisation, said such a device could be very helpful to those working on the helpline.
"If there is any way of finding out earlier the level of someone's risk of suicide, it would be a great help," she said.
The study is reported in the latest issue of New Scientist magazine.