Cochlear implant-mediated perception of nonlinguistic sounds

The overwhelming majority of test measures to assess cochlear implant (CI) candidacy, efficacy, and progress are based on speech perception. Nonlinguistic sounds, such as alerting and nonspeech human generated sounds, have received comparatively little attention, despite their central importance for daily living and environmental sound awareness. The purposes of this study were to develop and validate a beta test measure of nonlinguistic sound perception and to assess performance in CI users.

A beta test of nonlinguistic sound perception, referred to as the NonLinguistic Sounds Test (NLST) was developed. The NLST consists of 50 sound tokens distributed over five categories (animal, human nonspeech, mechanical/alerting, nature, and musical instruments). Both closed-set (category identification) and open-set (token identification) nonlinguistic sound perceptions were examined. Twenty-two postlingually deafened CI users (mean age, 59.4 +/- 10 yrs) were evaluated using common speech perception test measures (Hearing In Noise test and Consonant-Nucleus-Consonant words) and the NLST following a pilot study in which nonlinguistic sound tokens used were selected or eliminated.

The NLST was easily administered to all 22 CI subjects. An overall token identification score of 49 +/- 13.5% correct was obtained across all five categories. CI users were able to identify the correct category for 71 +/- 11.5% of tokens. A moderate correlation between speech perception and accuracy of nonlinguistic identification was found (r = 0.519, p = 0.016).

The results suggest that nonlinguistic sounds are difficult for CI users to perceive. The categorization and identification scores suggest that sounds with harmonic structure or sounds with repetitive temporal structure are easier for CI users to perceive. A further developed clinical version of the NLST may be a useful clinical test to measure CI performance and progress, and perception of nonlinguistic sounds should receive greater attention during postimplant auditory rehabilitation.