Maximum hearing loss is caused by

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.