Tuning fork and tests
- 1. Types Of Tuning Fork Tests & Clinical Findings
- 2. Tuning Fork The tuning fork is a device, usually made of steel, magnesium or aluminum that is used to tune musical instruments or by singers to obtain certain pitches. The tuning fork is set into vibration by holding the stem in the hand and striking one of the tines against a firm but resilient surface. 512 Hz is an ideal tuning fork. ◦ Tuning forks of lower frequency produce more bone vibration. ◦ Tuning forks of higher frequency have shorter decay time and are difficult to activate for them to be heard with a moderate or severe sensorineural impairment.
- 3. Principle of Tuning Fork The sound can be transmitted to cochlea in 2 ways: Air conduction (AC): Transmission of sound to the cochlea via external air and middle ear. Measures function of conducting pathway and cochlea. Bone conduction (BC): Transmission of sound to cochlea via vibration is skull (mastoid) bone, bypassing the external and middle ear. Measures function of cochlea only.
- 4. Types Of Tuning Fork Tests Nature Of Tuning Fork Tests Rinne test Compare air conduction & bone conduction test Weber test Bone conduction test Absolute Bone conduction (ABC) Bone conduction test Schwabach’s test Bone conduction test Bing test Bone conduction test Gelle’s test Bone conduction test
- 5. Rinne Test Method The clinician strikes a tuning fork and places it on the mastoid bone behind one ear. When a patient can no longer hear the sound, signal to the clinician. Then, the clinician moves the tuning fork next to ear canal. When a patient can no longer hear that sound, once again signal the clinician. Clinician ask whether the sound was louder at the beginning (bone conduction) or whether it became louder (air conduction). Clinician compares air conduction and bone conduction of same ear.
- 6. Rinne Test Results Test Normal Hearing Conductive Hearing Loss Total Hearing Loss Rinne AC > BC Positive Rinne or Sensorineural Hearing Loss AC < BC Negative Rinne AC = BC Mild CHL BC+ (heard from opposite ear) AC- (sound cannot be heard) False Negative Rinne
- 7. Weber Test Method The clinician strikes a tuning fork and places it on the middle of your head. Clinician note where the sound is best heard: ◦ The left ear. ◦ The right ear. ◦ Both equally.
- 8. Weber Test Results Normal hearing: Equal sound in both ears. Conductive loss: Sound to be heard best in the abnormal ear. Sensorineural loss: Sound to be heard best in the normal ear. Test Normal Hearing Conductive Hearing Loss Sensorineural Hearing Loss Weber Sound is heard at midline Sound is heard better in bad ear. Sound is heard better in good ear.
- 10. Schwabach’s Test The clinician strikes a tuning fork and places it on the mastoid bone of the patient. When patient raises hand that he has stopped hearing sound fork is placed at mastoid bone of clinician. Compare bone conduction of patient to the bone conduction of the clinician. Test details Interpretation Clinician and patient hear the fork for same duration Normal/ Conductive hearing loss Patient hear the fork for shorter duration Sensorineural hearing loss
- 12. Absolute Bone Conduction (ABC) Test Method Examiner closes the test ear by gently pressing the tragus against ear canal. Foot piece of vibrating tuning fork is kept over mastoid bone and patient listens to the fork till sound disappears completely. Immediately same fork is transferred over mastoid bone of the clinician and simultaneously ear canal is closed by pressing the tragus.
- 13. Absolute Bone Conduction (ABC) Test Results Test details Result Interpretation Clinician listens longer than patient ABC reduced SNHL Clinician listens equal to that of patient ABC normal Normal Patient listens longer than clinician ABC lengthened CHL
- 14. Bing Test Method This is like ABC test, but the external ear canal is alternately closed and opened by pressing and releasing the tragus. The vibrating fork is placed over the mastoid process and when it ceases to be heard the examiner’s finger is used to occlude the external auditory canal preventing sound from escaping via the external canal. Test details Result Interpretation Positive Bing test Louder when occluded Normal or SNHL Negative Bing test No change CHL
- 15. Gelle’s Test Method In this test, the air pressure in the external canal is varied using a Siegle’s speculum. The vibrating fork is held in contact with the mastoid process. In stapes fixation no alteration in the hearing threshold is evident. Siegle’s speculum
- 16. Gelle’s Test Result Test details Result Interpretation Positive Gelle’s test Decreased hearing Normal or SNHL Negative Gelle’s test Normal hearing Ossicular chain fixation (otosclerosis) or discontinuation
Editor's Notes
- #7: Normal hearing: air conduction time that is twice as long as the bone conduction time. Conductive hearing loss: the bone conduction is heard longer than the air conduction sound. Sensorineural hearing loss: air conduction is heard longer than bone conduction, but may not be twice as long.