Tuning Fork Tests

Tuning fork tests are a classic and essential method for assessing hearing, performed using a set of medical tuning forks. These tests are an integral part of the otolaryngological examination and serve both for rapid screening and, most importantly, for determining the type of hearing loss.

Tuning fork tests do not quantify the degree of hearing impairment. Their primary goal is to differentiate between conductive hearing loss (associated with impaired sound conduction) and sensorineural hearing loss (associated with dysfunction of the sound-perceiving apparatus).

Principle and Tools

The technique is based on comparing the patient’s perception of sound transmitted via two pathways:

• Air conduction (AC): Sound waves travel through the external auditory canal, tympanic membrane, and ossicular chain to reach the inner ear. This is the physiological route of sound perception.
• Bone conduction (BC): Vibrations are transmitted directly through the skull bones to the cochlea, bypassing the external and middle ear.

A set of tuning forks — most commonly C₁₂₈ (for vibratory sensitivity) and C₅₁₂ (for the Rinne and Weber tests, as its frequency falls within the human speech range) — is employed.

Core Tests and Interpretation

Several classical tests are used in combination to provide the healthcare professional with a comprehensive understanding of the auditory system’s status.

Rinne Test

• Procedure: The base of a vibrating tuning fork is placed on the mastoid process (to test bone conduction). Once the patient no longer hears the sound, the fork is moved in front of the external auditory canal (to test air conduction).
• Interpretation:
  • Positive Rinne (AC > BC): Air-conducted sound is heard longer than bone-conducted sound. This is considered normal or indicative of sensorineural hearing loss.
  • Negative Rinne (BC > AC): Bone-conducted sound is heard longer. This is a sign of conductive hearing loss.

Weber Test

• Procedure: The base of a vibrating tuning fork is placed on the midline of the vertex or forehead. The patient is asked which ear perceives the sound more loudly.
• Interpretation:
  • Sound is perceived equally in both ears: Normal hearing.
  • Sound lateralizes to the affected ear: The patient hears the sound better with the affected ear. This finding indicates conductive hearing loss on that side.
  • Sound lateralizes to the healthy ear: The patient hears the sound better with the healthy ear. This result suggests sensorineural hearing loss on the affected side.

Schwabach Test

• Procedure: The duration of bone-conducted sound perception is compared between the patient and the examiner (with normal hearing).
• Interpretation:
  • Shortened Schwabach: The patient hears the sound for a shorter duration than the examiner. This suggests sensorineural hearing loss.
  • Prolonged Schwabach: The patient hears the sound longer than the examiner. This is a sign of conductive hearing loss.

Clinical significance

Despite advances in audiometry, tuning fork tests remain indispensable for rapid bedside or outpatient hearing assessment. They allow healthcare providers to quickly obtain qualitative information about the nature of hearing loss prior to hardware-based evaluation. For example, a combination of a negative Rinne test and lateralization of sound to the affected ear in the Weber test is clearly associated with a conductive pathology. The results of tuning fork tests also aid in the accurate interpretation of audiograms and contribute to a comprehensive understanding of the patient’s auditory status.