This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Otosclerosis, Subject name: ENT
"Boiler's notch" is suggestive of ? 
Select and explain. 
A. Conductive Hearing Loss, B. Noise Induced Hearing Loss (NIHL), C. Both 1 and 2, D. Normal Finding
B: Noise Induced Hearing Loss (NIHL)
Answer: B: Noise Induced Hearing Loss (NIHL) 
Explanation: Boiler notch/Acoustic dip is seen in Noise induced hearing loss NIHL Boiler notch at 4000Hz Notch is seen in BC curve AC curve notch are insignificant Maximum seen at 3000-6000Hz Sound causing maximum NIHL 2000-3000Hz Stereocilia of Outer hair cells are first to be affected