Hearing Physiology

A 58-year-old male factory worker presents with progressive bilateral hearing loss over the past 10 years. He reports difficulty hearing high-pitched sounds and conversations in noisy environments. Audiometry shows a characteristic dip at 4 kHz bilaterally. Tympanometry is normal. He denies tinnitus, vertigo, or otalgia. Otoscopy reveals no cerumen impaction or tympanic membrane abnormality. What is the most likely mechanism of hearing loss in this patient?

A 72-year-old woman is evaluated for bilateral hearing loss that has worsened over the past 20 years. She reports difficulty understanding speech, especially in the presence of background noise. Audiometry reveals a gradual, symmetrical high-frequency sensorineural hearing loss affecting all frequencies, worse at higher frequencies. Bone and air conduction thresholds are equally elevated. MRI of the internal auditory canal is normal. What is the primary site of pathology in this patient's auditory system?

Which of the following structures in the inner ear is responsible for converting mechanical vibrations into electrical signals?

At which frequency does the basilar membrane show maximum displacement at the basal (stapes) end of the cochlea?