Recognition of digits in different types of noise by normal-hearing and hearing-impaired listeners

The objective of the study was to examine the ability to understand digits in different types of noise. Adaptive speech-in-noise tests were developed that measure the speech-reception-threshold (SRT.) i.e. signal-to-noise ratio that corresponds to 50% intelligibility. Digits were presented in continuous noise, 16-Hz interrupted noise, and 32-Hz interrupted noise. Also the standard Dutch triplet SRTn test in continuous noise was included. Results for forty-two ears of normal-hearing and hearing-impaired adult participants are presented. The ratio between the standard deviation in SRTn values between subjects and the measurement error determines the efficiency of the tests. A high efficiency could be achieved by using triplets instead of digits, or by using 16-Hz interrupted noise instead of continuous noise, because this resulted in a large spread in SRT, values. The simple calculation method of averaging presentation levels was highly efficient. The digit SRT, test in 16-Hz interrupted noise was very efficient in discriminating between normal-hearing listeners and hearing-impaired listeners, and might be used to screen for hearing loss as measured by pure-tone audiometry.