Tuning Fork Tests and Otosclerosis

A 32-year-old woman presents with three months of progressive left-sided hearing loss and low-frequency tinnitus. She reports improved hearing in noisy environments. On examination, the left tympanic membrane shows a subtle pink blush over the promontory. Bedside tuning fork tests with 512 Hz fork show: Weber test lateralizes to the left ear; Rinne test shows bone conduction perceived longer than air conduction on the left (BC>AC), while air conduction is perceived longer than bone conduction on the right (AC>BC). Pure-tone audiometry reveals a 25–30 dB air-bone gap on the left with a characteristic dip at 2 kHz on bone conduction (Carhart notch). The audiogram pattern shown in **C** is most consistent with which diagnosis?