This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: ENT
Tone decay test is done for: 
Select and explain. 
A. Cochlear deafness, B. Neural deafness, C. Middle ear problem, D. Otosclerosis
B: Neural deafness
Answer: B: Neural deafness 
Explanation: (b) Neural deafness(Ref. Anirban Biswas, 5th ed. 56)Tone decay is a function of nerve fatigue.If the nerves are fatigued the patient stops hearing a sound given to him continuously before the completion of 1 minute.A tone decay of more than 30dB is suggestive of retrocochlear or neural deafness