This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hearing Loss, Subject name: ENT
[{'content': "What should be the loss of hearing at least for Weber's test to lateralise? \nSelect and explain. \nA. 5 db, B. 10 db, C. 15 db, D. 20 db", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. a (5 db). (Ref. Diseases of ENT by PL Dhingra, 2nd ed., 26; 3rd ed., 30)# Lateralization of sound in Weber test, a tunning fork of 512 Hz implies a conductive loss of 15-25 dB in ipsilateral ear or a sensorineural in contralateral ear.# However as less as 5 db hearing loss can cause lateralization of Weber's test.# A negative Rinne's test indicates a minimum air-bone gap of 15-20 db. TestNormalConductive deafnessSensorineural deafness1Rinne's testAC > BC (Rinne +)BC > AC (Rinne -)AC > BC2Weber's testNot lateralisedLaterlized to poor earLateralized to better ear3ABCSame as examinersSame as examinersReduced4Schwabach's testEqualLengthenedShortened", 'role': 'assistant'}]