A 42-year-old woman presents with bilateral hearing loss first noticed in her early 20s that has remained stable for 15–20 years. Her father, paternal grandfather, and two of her three children have identical hearing loss patterns. Audiometry shows normal thresholds at 250–500 Hz, moderate-to-severe loss at 1000–2000 Hz, and relative preservation at 4000–8000 Hz, creating a characteristic U-shaped cookie-bite pattern. The region marked **B** in the diagram represents the maximally affected mid-frequency thresholds at 1000–2000 Hz. Molecular testing confirms a heterozygous missense mutation in the TECTA gene. Which of the following best explains the pathophysiology of hearing loss at the frequency range marked **B**?