Clinical Importance of Sound-Field Speech Recognition Test for Measurement of Hearing Aid Benefit

Abstract

Background and Objectives Although sound-field speech recognition test is an essential evaluation method to verify the benefit of hearing aids, the aided sound-field speech recognition test has not been used as a standard audiometric protocol. This study investigated whether a traditional measure of unaided speech recognition measured at an individual’s most comfortable level (MCL) can predict aided speech recognition performance and the benefit of hearing aids.Subjects and Method One hundred twenty-one ears (72 adult hearing aid users) with moderate, moderately severe, and severe degrees of hearing loss were tested. The word recognition score (WRS) and sentence recognition score (SRS) were measured at MCLs using earphones (earphone WRS and earphone SRS). From the sound-field speech audiometry, both unaided and aided WRS and SRS were evaluated at an average conversational speech level (at 65 dB SPL) using a loudspeaker (located at 0° azimuth, 1 m). This study determined the differences between earphone scores (at MCL) and aided recognition scores (at 65 dB SPL), which is known as earphone to aided difference (EAD). Also, the hearing aid benefit was simply derived by differences between the unaided and aided scores, both measured at 65 dB SPL.Results The differences between the unaided and aided scores were significantly lower with a higher degree of hearing loss, yet the earphone scores measured at MCLs did not differ across varied hearing loss. More than half of the tested ears had the EAD of greater than ±10%. The ears with a higher degree of hearing loss tended to have +EAD (earphone score>aided score), whereas the ears with less hearing loss showed -EAD (earphone score≤aided score). The earphone score measured at MCLs was not a predominant contributor to predict either aided performance or hearing aid benefit.Conclusion Clinicians should not assume that the unaided speech recognition score measured with earphones at MCL can accurately predict aided speech recognition or the benefit of hearing aids. Instead, it is crucial to directly assess aided sound-field speech recognition performance at a conversational speech level.