Evaluating performance with high-frequency emphasis amplification.

Hearing aid fitting for individuals with high-frequency impairment has been difficult because of the limited gain available at those frequencies. Special high-frequency emphasis hearing aids have been developed in an attempt to alleviate this problem. The insertion-gain responses and changes in speech-recognition performance (in quiet and in noise, aided and unaided) were measured for a commercially available high-frequency emphasis hearing aid, using two types of speech materials (nonsense syllables, monosyllabic words). The maximum obtainable gain observed for high frequencies approximated that prescribed by the NAL-R method, but was considerably lower than that prescribed by other common prescriptive methods. Furthermore, modest improvements in speech recognition were found. When evaluating individuals with high-frequency impairment, speech materials administered in noise appeared to be the most sensitive indication of improved speech recognition. Special high-frequency emphasis speech materials (CUNY NST) were no more sensitive to improvements in performance than conventional clinical word lists (NU6).