Principle: This test is useful in identifying unilateral hearing loss. A patient with a unilateral conductive hearing loss (CHL) would hear the tuning fork loudest in the affected ear. Weber test is lateralized to better ear.Masking opposite ear with Barany’s noise box to prevent transcranial transmission of sound.On application of vibrating tuning fork to deaf side the sound is transmitted to the non-test ear by bone and patient perceives this bone conduction and presumes that it is perceived by test ear, thus interpreting it as BC > AC.Īssociated conditions: Congenital causes, Skull fracture, Meningitis, Mumps, Acoustic neuroma This is seen when a patient has severe SNHL on test side and normal hearing on non-test side. Test of duration should be performed to confirm. Note: Sometimes, in testing for loudness AC = BC can be noted and this may indicate mild CHL. Ask the patient if loudness of AC or BC is greater?.Ask if he can still hear the sound or not?.After the patient signals, quickly bring the tuning fork in the position to test AC.Ask patient to signal as soon as he ceases to hear the sound.Since, the cochlear mechanism is same for both the routes, Air conduction (AC) tests the whole ear (conductive and senorineural component) while Bone conduction (BC) tests only the senosrineural component. Bone conduction (BC): Transmission of sound to cochlea via vibration is skull bone, bypassing the external and middle ear.Air conduction (AC): Transmission of sound to the cochlea via external air and middle ear.The sound can be transmitted to cochlea in 2 ways:
Principle of Air Conduction (AC) and Bone Conduction (BC) Tuning forks of higher frequency have shorter decay time (how fast the tuning fork loses vibratory energy) and are difficult to activate for them to be heard with a moderate or severe sensorineural impairment. Tuning forks of lower frequency produce more bone vibration. Why tuning fork of 512 Hz is ideal for hearing tests? Strike the junction of superior 1/3 and inferior 2/3 of the prongs (area of maximum vibration) on a rubber pad or elbow.Hold the stem of the tuning fork between the index finger and thumb of your right hand without touching the prongs.Principle of Air Conduction (AC) and Bone Conduction (BC).Why tuning fork of 512 Hz is ideal for hearing tests?.
0 kommentar(er)
