Presbycusis Older Adult

A 72-year-old man presents to the ENT clinic with a 5-year history of progressive difficulty understanding speech, particularly in noisy environments. His wife reports he often asks people to repeat themselves, especially when they speak quickly. Audiometry shows bilateral symmetric sensorineural hearing loss with high-frequency predominance. Tympanometry is normal. The pattern shown as **A** in the diagram is most consistent with presbycusis. Which of the following is the MOST COMMON pathophysiologic mechanism underlying this patient's presentation?