Trough-shaped curve in audiometry is seen in

Trough shaped curve (B-type) in audiometry is seen in secretory otitis media. Type A -Normal tympanogram. Type As- Compliance is lower at or near ambient air pressure. Seen in fixation of ossicles, e.g. otosclerosis or malleus fixation. Type Ad- High compliance at or near ambient pressure. Seen in the ossicular discontinuity or thin and lax tympanic membrane. Type B - flat or dome-shaped graph- No change in compliance with pressure changes. Seen in middle ear fluid or thick tympanic membrane. Type C- Maximum compliance occurs with negative pressure in excess of 100 mm H2O. Seen in a retracted tympanic membrane and may show some fluid in middle ear. Ref: Dhingra; 6th Edition; pg no 24