Tuning Forks: Frequencies and Clinical Uses

Two frequencies cover almost all bedside use, and they are not interchangeable.

128 Hz — vibration sense

Low frequency, long decay, and usually weighted with mass at the tines to sustain the vibration.

Used to test vibration sense over bony prominences — the medial malleolus, the first metatarsophalangeal joint, the styloid process. Loss of vibration sense is an early sign in peripheral neuropathy, which makes this fork routine in diabetic foot assessment.

Given diabetes prevalence in Singapore, a 128 Hz weighted fork earns its place in any general practice.

512 Hz — hearing

Higher frequency, unweighted, and the standard for Rinne and Weber tests distinguishing conductive from sensorineural hearing loss.

512 Hz is the accepted compromise: low enough to be felt as bone conduction, high enough to be heard clearly as air conduction. 256 Hz is sometimes used but is more easily felt rather than heard, which confounds the result. 1024 Hz decays too quickly.

Why the wrong fork misleads

Using a weighted 128 Hz fork for Rinne gives a stimulus the patient may feel rather than hear — so a "positive" result can reflect tactile perception, not hearing. Using 512 Hz for vibration sense gives a stimulus that decays too fast to assess threshold properly.

Practical points

• Strike on a firm but yielding surface — the heel of your hand or your knee. Striking metal or a table edge produces overtones and can chip the tines.
• Strike consistently. Amplitude affects the result, so a reproducible strike matters.
• Stainless steel holds pitch and can be disinfected. Aluminium is lighter and cheaper but less durable.
• Chipped or bent tines change the frequency. Retire a damaged fork rather than using it.

Forks are in tuning forks, with the wider set in neurological testing.

See also reflex hammers compared and the diagnostic kit guide.

Browse the range in our diagnostic equipment collection.