Which of the following best describes insertion loss?

• A. The decrease in natural amplification of the ear when the external auditory canal is closed off
• B. The difference between coupler gain and real-ear gain
• C. The variation in signal reaching the hearing aid microphone
• D. Real-ear aided response minus real-ear unaided response

Answer: (A)

Insertion loss is the reduction of the ear’s own natural amplification that occurs when the external auditory canal is occluded, such as when a plug or earmold fills the canal. When the canal is open, the ear canal and pinna contribute some amplification through their resonances; blocking the canal reduces that natural amplification, especially at higher frequencies. This is what insertion loss describes. The other options talk about different measurements: the gap between coupler gain and real-ear gain relates to how device measurements compare to standardized conditions, not the ear’s own amplification; variation in signal reaching the hearing aid microphone isn’t about the ear’s natural amplification; and real-ear aided minus real-ear unaided describes the device’s gain (insertion gain) rather than the ear’s loss when occluded.