Dichotic listening to speech: background and preliminary data for digits, sentences, and nonsense syllables.

Three tests of dichotic listening utilizing speech signals as stimuli are included on the VA-CD Tonal and Speech Materials for Auditory Perceptual Assessment, Disc 1.0. They include a dichotic monosyllabic digits task, a dichotic synthetic sentences task, and a dichotic nonsense syllable (CV) task. Since the materials were specially recorded or created and recorded for use on the VA-CD, normative data were collected at nine universities/medical centers in the United States involving 120 young listeners. Data revealed that these listeners had little difficulty correctly identifying digits or synthetic sentences when they were presented at 50-70 dB HL in a dichotic format requiring two responses to each trial. At the same presentation levels and under two onset-time conditions (0- and 90-msec onset stagger), correct responsiveness was less frequent when the stimuli were dichotic CVs. However, scores fell in ranges consistent with previous studies and useful for seeking lesion effects. Although careful definition of stimuli, standardization of materials, and the relative stability offered by audio compact disc technology were prime reasons for making the VA-CD, another goal was to offer the clinician-researcher a range of difficulty among the procedures on the disc. Data from the normative trials using dichotic speech signals suggest that the goal has been accomplished.