<prompt> Carharts notch in otosclerosis is observed at: Repeat1000 HZ2000 HZ3000 HZ4000 HZ  <response>: Ans: B 2000HZ Ref: Diseases of the Ear Nose and Throat by PL Dhingra 5th edn .2010.pg 97-100Explanation:Carharts notchCarharts notch is classically seen as a dip centered around 2 kHz range of hone conduction curve audiometery.This feature is seen in patients with otosclerosis.This notch will disappear after a succesful stapedotomyThere is also effective improvement in the patients level of hearing at 2 KHz frequency levels. 