Serous Otitis Media Type B Flat Tympanogram Middle Ear Effusion

A 5-year-old boy presents with poor academic performance, inattention in class, and speech-language delay. His parents report he frequently asks for TV volume to be increased. Otoscopy reveals bilateral dull, retracted tympanic membranes with yellow-amber discoloration and visible air-fluid levels. Tuning fork testing shows Weber midline and Rinne negative bilaterally. Pure-tone audiometry demonstrates bilateral symmetric mild-to-moderate conductive hearing loss with an air-bone gap of 28 dB, worse in low frequencies, and normal bone-conduction thresholds. The pattern marked **A** in the audiogram and tympanogram—bilateral mild conductive loss with type B flat tympanograms—is diagnostic of which condition?