Subjects exhibiting a behavior pattern (type A) previously found to be associated with a high prevalence and incidence rate of clinical coronary heart disease (CHD) and patients suffering from clinical coronary heart disease were subjected to a specially designed "voice analysis" test. Approximately 84% of the type A subjects and 76% of the patients with CHD responded to this test in a manner that allowed their differentiation from well subjects exhibiting a behavior pattern (type B) previously found to be associated with a low prevalence and incidence rate of CHD.
Friedman M, Brown AE, Rosenman RH. Voice Analysis Test for Detection of Behavior PatternResponses of Normal Men and Coronary Patients. JAMA. 1969;208(5):828–836. doi:10.1001/jama.1969.03160050082008