Amplification characteristics of the Hearing Aid Program in AirPods Pro 2

The AirPods Pro 2® (Apple Inc., Cupertino, CA, USA) recently received regulatory approval in Japan as a Class II medical device incorporating a self-administered hearing assessment feature ("Hearing Check") and a hearing assistance program ("Hearing Aid Program"). Unlike conventional prescription hearing aids fitted using prescriptive algorithms such as NAL-NL2 and DSL v5, the amplification characteristics of the AirPods Pro 2 Hearing Aid Program are automatically determined by proprietary algorithms based on device-derived thresholds, and internal processing parameters are not publicly disclosed. To characterize the level-dependent real-ear insertion gain (REIG) generated by the AirPods Pro 2 Hearing Aid Program across representative audiometric profiles and to compare its gain characteristics with NAL-NL2 and DSL v5 prescriptive targets.

Five representative audiometric profiles (30-dB flat, 50-dB flat, low-frequency hearing loss, gradually sloping high-frequency loss, and steeply sloping high-frequency loss) were selected from an independent dataset obtained using the AirPods Hearing Check. These profiles were sequentially programmed into the device for real-ear measurements in 10 adult volunteers (10 right ears). REIG was measured using the International Speech Test Signal at input levels of 50, 65, and 80 dB SPL in a calibrated sound-treated booth. Measured REIG was descriptively compared with prescriptive targets calculated from the same device-derived thresholds.

REIG varied according to audiometric profile and input level. Gain generally increased toward mid- and high-frequency regions relative to low frequencies. Insertion gain progressively decreased as input level increased, with marked attenuation at 80 dB SPL. Compared with prescriptive targets, measured REIG was generally lower and showed less pronounced frequency-specific gain variation.

The AirPods Pro 2 Hearing Aid Program exhibits nonlinear, level-dependent amplification with moderate frequency shaping and attenuation at higher input levels. Its gain characteristics differ from conventional prescriptive targets, suggesting emphasis on listening support and output control rather than strict prescriptive matching. Further studies are needed to clarify the clinical role of consumer-oriented hearing devices.