<prompt> Maximum hearing loss is caused byOssicular chain damageTympanic membrane perforationObliteration of oval windowBlockage of ear canal  <response>: 1. Complete obstruction of ear canal: 30 dB 2. Perforation of tympanic membrane. It varies and is directly propoional to the size of perforation: 10-40 dB 3. Ossicular interruption with intact drum: 54 dB 4. Ossicular interruption with perforation: 38 dB 5. Malleus fixation: 10-25 dB 6. Closure of oval window: 60 dB Ref: Dhingra 7e pg 31. 