Abstract
The effect of the frequency response of a hearing aid on the interrelationship among the most comfortable level (MCL), uncomfortable level (UCL) and speech discrimination score was studied in relation to hearing-aid fitting. Measurements of MCLs, UCLs and speech discrimination scores at the MCL were performed using three different low frequency cut-off slopes of the hearing aid. Twelve individuals with moderately severe sensorineural hearing losses served as subjects.
Low-frequency amplification resulted in elevation of both the MCL and UCL. The degree of elevation of the MCL was larger than that of the UCL. Therefore, low-frequency amplification provided wide audible areas to hearing-aid users. The results also indicated that low-frequency amplification provided good speech discrimination scores for nasals and voiced consonants. On the other hand, high-frequency amplification provided good discrimination scores for voiceless consonants.
Thus, the frequency response for widening the audible area is contrary to that for improving the intelligibility of voiceless consonants. This important problem must be taken into consideration in selecting the suitable frequency response of a hearing aid for an individual with hearing loss.
