Acoustical correlates of near-term suicidal risk

In the course of many years of clinical work in emergency rooms and office consultation with suicidal patients, clinicians have often successfully predicted suicidality based on the vocal patterns of the patients, independent of the content. Vocal sound and clinical substance reciprocally augmented each other in determining the near-term risk [M. K. Silverman and S. E. Silverman, ‘‘From sound to silence: A preliminary investigation of the use of vocal parameters in the prediction of near-term suicidal risk,’’ submitted to J. Med. Psychotheraphy]. Vocal patterns heard as representing a ‘‘hollow,’’ ‘‘toneless’’ sound were designated unanimously as the most compelling feature in suicidal voices. Motivated by qualitative descriptions of experienced clinicians, a quantitative study was carried out that investigated the acoustic correlates of near-term risk. The audio tapes selected for this research were suicide notes left on tapes donated by survivors, recordings of several patients who had been hospitalized, and recordings of 911 suicide in progress calls. This research is concerned with realistic speech data encountered in real-life situations due to the inability to study suicidal behavior in any kind of controlled setting. To compensate for spectral variability introduced by different recording environments, robustness techniques such as long-term mean removal and frequency warping were utilized. The relative significance of resonant frequencies and frequency bands in terms of their ability to predict the near-term suicidal risk was evaluated. Preliminary results suggest that the frequency spectrum patterns of the suicidal voice may have utility in the assessment of near-term risk.