Relationships among speech threshold, loudness discomfort, comfortable loudness, and PB max in the elderly hearing impaired.

The purposes of this study were (1) to determine the effect of the severity of hearing loss on the most comfortable loudness level (MCL) and the loudness discomfort level (LDL), and (2) to assess the efficacy of obtaining maximum intelligibility (PB max) at MCL and/or LDL. One hundred twenty-nine ears were tested from seventy-four elderly subjects having mild to moderate sensorineural hearing losses. The results showed that mean MCLs and LDLs remained fairly constant as spondaic thresholds increased from 5 to 55 dB HTL. The data also exhibited considerable intersubject variability and indicated that MCLs and LDLs could not be closely predicted from threshold. Thus, for most clinical purposes MCL and LDL must be measured directly. This study also indicated that measuring speech intelligibility at MCL approximated PB max (+/- 12 percent) only about two-third of the time. Thus, decisions concerning auditory functioning may frequently be inaccurate if intelligibility is measured only at MCL. Neither can LDL be the single intensity at which speech intelligibility is measured, at least with elderly patients, since one in ten scores did not closely approximate PB max. Consequently, we concur with previous investigators who recommend generating an entire intelligibility function. The present findings also suggest that hearing aid users may not receive optimal benefit if their hearing aid is adjusted to MCL, and that improved intelligibility may be achieved a higher volume control settings. The hearing aid evaluation process should investigate this possibility.