Outer hair cell damage compresses dynamic range, causing recruitment and distorted loudness perception

Evidence

For a sensorineural impairment, the type of attenuation depends on whether the inner or outer hair cells are damaged. If the inner hair cells are damaged, the attenuation is not dependent on the sound level. However, if the outer hair cells are damaged, the resulting attenuation of sound is more prominent at low input levels. This is because when the outer hair cells are damaged, the input-level-dependent amplification provided by them does not function properly. Consequently, loud sounds may be heard normally, but quiet sounds are attenuated. This phenomenon is called recruitment. Due to recruitment, a change in SPL translates into an abnormally large change in loudness. Moreover, the range of sound pressure levels from the hearing threshold to the loudness discomfort level is decreased. Consequently, dynamic changes in sound level are overemphasized, and sound is often perceived to be either too loud or too quiet. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2655

Categorization

• DEFINE: Defines recruitment as the phenomenon where quiet sounds are attenuated but loud sounds are normal due to outer hair cell damage.
• XREF: Connects to complaints about hearing aids overcompensating for loud sounds — the loudness discomfort level shrinks precisely because recruitment overemphasizes dynamic range. — connects to: Noise-induced hearing loss begins with impairment of outer hair cells; Outer-hair-cell damage destroys the cochlea’s compressive nonlinearity, which hearing aids try to rebuild.; Fiber-type-specific damage produces distinct loudness perception abnormalities. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 737 (+4 more)
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2655

Broader Connections

• Outer hair cell damage widens critical bands and worsens speech-in-noise #expands (0.85) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2670
• Loudness recruitment shrinks dynamic range while preserving overall loudness #expands (0.80)
• Loudness growth mirrors basilar membrane input-output functions #qualifies (0.70)