The Weber test is a rapid clinical screening procedure used to detect asymmetrical (unilateral) hearing loss. This simple assessment utilizes a vibrating tuning fork to evaluate bone conduction, where sound vibrations travel directly through the skull bones to stimulate the inner ear. By bypassing the outer and middle ear structures, the Weber test helps determine if a hearing deficit is due to sound transmission issues (conductive loss) or sound processing issues (sensorineural loss).
Preparing for the Test
The necessary equipment for the Weber test is a tuning fork, typically one with a frequency of 512 Hz. This frequency is preferred because it balances maintaining the tone for a sufficient duration and minimizing tactile vibration that a patient might mistake for sound. Lower frequencies, such as 256 Hz, tend to produce a strong vibration sensation that can confuse the test results.
The test environment must be quiet so the patient can clearly perceive the bone-conducted sound without interference from ambient noise. The patient should be sitting comfortably and instructed on the task before the procedure begins. The examiner must explain that they will place a vibrating instrument on the head and that the patient needs to report where they hear the sound loudest: in the left ear, the right ear, or equally in the center of the head.
Executing the Weber Test Procedure
The test begins with activating the tuning fork by holding the stem and striking one of the tines against a soft surface, such as the examiner’s elbow or the ball of their hand. Avoid striking the fork against a hard surface, as this can introduce non-harmonic frequencies that interfere with the purity of the tone.
Once the fork is vibrating, the examiner places the base of the stem firmly against the patient’s head at the midline. Common placement sites are the center of the forehead or the vertex (the very top of the head), equidistant from both ears. For optimal sound transmission, the examiner can gently apply counter-pressure with their other hand on the opposite side of the patient’s head.
The patient is given a few seconds to perceive the sound and is asked to immediately report where the sound is heard loudest. This phenomenon of the sound being heard louder in one ear is called lateralization. As soon as the patient provides their answer, the vibrating fork should be removed, and the result is recorded.
Understanding the Test Results
The interpretation of the Weber test is based entirely on the patient’s report of lateralization, which helps distinguish between two primary types of hearing loss. If the patient reports hearing the sound equally in both ears or in the center of the head, the result is considered normal. This finding suggests either that the patient has no hearing loss or that any existing hearing loss is symmetrical in both ears.
When the sound lateralizes (is heard louder) in the ear that has a hearing problem, this outcome suggests a conductive hearing loss in that ear. Conductive loss is caused by issues in the outer or middle ear that block the transmission of air-conducted sound. The sound seems louder in the affected ear because the blockage prevents environmental noise from reaching the inner ear, reducing the masking effect and allowing the bone-conducted sound to be perceived more clearly.
Conversely, if the sound lateralizes to the ear with better hearing, it suggests a sensorineural hearing loss in the opposite, poorer-hearing ear. Sensorineural loss involves damage to the inner ear structures, like the cochlea, or the auditory nerve itself. The sound is perceived louder in the unaffected ear because the damaged inner ear on the other side cannot effectively process the bone-conducted vibrations. The Weber test can detect a difference as subtle as five decibels between the bone conduction thresholds of the two ears.