Effects of Adding Monaural and Binaural Noise to a Dichotic Listening Task

Abstract

The Dichotic Digits Test (DDT) evaluates central auditory nervous system (CANS) dysfunction. The DDT is widely used in audiology clinics worldwide, because it is clinically efficient and has good sensitivity and specificity for CANS lesions. However, the DDT shows a strong ceiling effect, which can mitigate its ability to detect subtle CANS dysfunction. This study examines the effects of adding monaural and binaural speech-spectrum noise to the DDT, in an effort to make the test more challenging to the CANS and thereby reduce the observed ceiling effect. Effects of monaural and binaural noise on different DDT scoring indices, including Individual Ear Percent Correct Scores, Combined Total Percent Correct Scores, and Dichotic Difference Scores, as well as noise effects on the Right Ear Advantage for speech, are investigated here. Statistically significant differences on all indices were found between monaural and binaural noise-added conditions, suggesting a possible advantage for binaural listening in noise. These preliminary findings suggest that adding noise to tests of dichotic listening and assessing dichotic listening patterns in noise could add sensitivity to evaluations of CANS integrity and function. Keywords: binaural hearing, ceiling effect, central auditory processing, dichotic listening, neuroaudiology, Right Ear Advantage, speech-in-noise