Development of the ORCA Nonsense Syllable Test

Abstract

Many new processing features in hearing aids have their primary effects on information located in the high frequencies. Speech perception tests that are optimized for evaluating high-frequency processing are needed to adequately study its effects on speech identification. The goal of the current research was to develop a medium for evaluating the effects of high-frequency processing in hearing aids. A list of 115 consonant-vowel-consonant-vowel-consonant nonsense syllables with American English consonants in all word positions was created in an open-set phoneme identification format. The source material was spoken by a male and a female speaker. A custom computer program was developed for administration of the test and automatic analysis of the test results. Nine normal-hearing listeners were employed in the collection of the normative data. The test was presented to the listeners in quiet (at 68 dB SPL), in noise at five signal-to-noise ratios (SNRs; -10, -5, 0, 5, and 10), and in a low-pass filter condition with cutoff frequencies at 500, 1000, 1500, 2000, and 4000 Hz. The data were examined to evaluate the psychometric properties of the test for different phoneme positions and phoneme classes. In addition, a shortened version of the test was developed based on the data from normal-hearing listeners. The test-retest reliability was verified at 0 dB SNR. The full and shortened versions of the test were repeated in 10 hearing-impaired listeners at their most comfortable listening level in quiet and in noise at various SNRs. The availability of high-frequency output was verified with acoustic analysis. The performance intensity functions for both versions of the test (i.e., male and female speakers) showed expected monotonic growth with SNR and cutoff frequencies. High reliability was seen between test and retest identification scores in normal-hearing and hearing-impaired listeners. The current nonsense syllable test provided a reliable and efficient means for phoneme identification testing.