Prescribing Amplification for Children: Adult-Equivalent Hearing Loss, Real-Ear Aided Gain, and NAL-NL1

Abstract

This paper focuses on how the acoustical differences between the ear canals of adults and children affect amplification requirements and describes efficient strategies to allow for these differences when prescribing and verifying amplification. We will first summarize the problem for hearing assessment and then describe how adult-equivalent hearing loss can be calculated to circumvent this problem. Example cases demonstrate manual calculation and automatic derivation by using the NAL-NL1 software. The advantage of using real-ear aided gain prescriptions rather than real-ear insertion gain prescriptions for young children is explained. The practical benefit of deriving coupler gain targets to achieve the required real-ear aided gain by using individually measured real-ear-to-coupler differences is emphasized, together with a discussion on the practical issues relating to calibration and probe tube placement in measuring real-ear-to-coupler differences. Finally, an illustrative case exemplifies the derivation of individualized coupler gain targets by using the NAL-NL1 software system to achieve the required real-ear aided gain for a young child.