Patent US 5,776,055

An apparatus and method are described for detecting and measuring the physiologic response of a subject to chemical intake to determine impairment due to alcohol, inhalant, illicit drug or prescription medication. The method includes transducing a set of words spoken by the subject into electrical signals which are amplified and frequency band-limited and then Fast Fourier Transformed to obtain the frequency spectra of the speech. The ratio of speech energy in a first bandpass region with respect to energy in another bandpass region which may include the first region is computed and utilized to produce an output signal which is a measure of the subject's degree of chemical impairment.