Tuning Fork - Parts, Types, and Uses

Parts of a Tuning Fork

Types of Tuning Forks

"The most useful fork is the 512-Hz fork, but 1024 Hz and 2048 Hz may also be used. Typically, tuning forks for frequencies below 512 Hz, such as 128 or 256-Hz, are not used [for hearing tests] because the low-frequency vibrations may be felt rather than heard. This somatosensory stimulation may confuse the patient and compromise findings."

• K.J. Lee's Essential Otolaryngology, p. 2834

"The most commonly used forks are the 256 Hz and 512 Hz forks, as these give more reliable responses than the 1024 Hz fork."

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol 2

Uses of Tuning Forks

1. ENT / Audiology - Hearing Assessment

Rinne Test (512 Hz)

• Method: Vibrating fork placed against the mastoid process (BC), then held 2 cm from the ear canal (AC). Patient says which is louder.
• AC > BC (Positive Rinne): Normal hearing OR sensorineural hearing loss
• BC > AC (Negative Rinne): Conductive hearing loss (air-bone gap of ≥20 dB with 512 Hz fork)
• The threshold comparison method can also be used: hold fork near ear until inaudible, then place on mastoid - if heard again, BC > AC.

• Shambaugh Surgery of the Ear, p. 205

Weber Test (512 Hz)

• Method: Vibrating fork placed on the forehead, nasal dorsum, or mandibular symphysis (midline). Patient reports which ear hears it louder.
• Lateralizes to the affected ear: Conductive hearing loss on that side (typically ≥3-5 dB gap)
• Lateralizes to the opposite ear: Sensorineural loss on that side
• No lateralization (midline): Normal, or symmetric loss

• Shambaugh Surgery of the Ear, p. 205; Scott-Brown's Vol 2

Bing Test

• Method: Activated fork placed on mastoid, then the ear canal is occluded with a finger.
• If occlusion makes the sound louder → normal hearing or sensorineural loss (Bing positive)
• If occlusion produces no change → conductive hearing loss (Bing negative)
• Based on the occlusion effect: blocking the external canal increases bone conduction only when the ossicular chain is intact.

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol 2

Schwabach Test

• Compares patient's bone conduction to the examiner's (assumed normal).
• Vibrating fork placed on patient's mastoid; when patient can no longer hear it, placed on examiner's mastoid.
• Diminished Schwabach: Patient stops hearing before examiner → sensorineural loss
• Prolonged Schwabach: Patient hears longer than examiner → conductive loss

2. Neurology - Vibration Sense Testing (128 Hz)

• Method: Strike fork, place the flat base on bony prominences - great toe, medial malleolus, patella, anterior tibia, sternum, finger joints.
• Patient reports when vibration starts and stops.
• Timed vibration test: Apply 128 Hz fork, count seconds patient perceives vibration. Compare against normal or opposite limb.
• Diminished vibration sense suggests peripheral neuropathy (e.g., diabetes, B12 deficiency) or dorsal column disease.

"Vibration sense is tested by placing a tuning fork with a..." - Adams and Victor's Principles of Neurology, 12th Ed.

"Vibration is tested by placing a 128-cycles/sec tuning fork on the bony prominences of the extremities and asking the patient to identify when it stops vibrating." - Textbook of Family Medicine, 9th Ed.

3. Neurology - Temperature Sensation Testing

"Temperature sensation can be tested with a cool piece of metal such as a tuning fork." - Neuroanatomy through Clinical Cases, 3rd Ed.

4. Diagnosing Stress Fractures

How to Properly Activate a Tuning Fork

• Strike it lightly against a soft surface (elbow, thenar eminence, rubber pad) - never a hard surface.
• Striking on a hard surface produces harmonics/overtones that distort the pure tone and give unreliable results.
• The fork should generate sound only when brought close to the ear (approximately 70 dBA at the ear).

Summary Table