Tests for bone conduction TestPrincipleMethodImpressionBing test Examines the effect of occlusion of ear canal on hearing Tuning fork placed on mastoid while examiner alternatively closes & opens the ear canal by pressing on the tragus inwards Patient hears louder when ear canal is occluded & softer when ear canal is open - Normal persons or sensorineural deafness ( Bing + ve )No change on ear canal opening or occlusion - conductive deafness ( Bing - ve )Gelle's test Examines the effect ofincreased air pressure in ear canal on hearing Placing a vibrating fork on mastoid while changes in air pressure in ear canalare brought about by siegel's speculum Positive - normal persons or sensorineural deafnessNegative - ossicular chain fixed or disconnected(Refer: PL Dhingra, Textbook of Ear, Nose, Throat, 6thedition,pg no: 21,22,23)