The Weber test is a rapid, non-invasive clinical screening method used to assess hearing symmetry between the left and right ears. This simple examination relies on the principle of bone conduction, transmitting sound vibrations directly through the skull to the inner ear. By bypassing the outer and middle ear structures, the test provides a quick snapshot of how sound is perceived by the inner ear and auditory nerve. It offers important initial clues about the presence and general nature of a potential hearing loss.
How the Weber Test is Performed
The procedure for the Weber test requires a tuning fork, typically calibrated to 512 hertz (Hz). This specific frequency is preferred because it offers the best balance between maintaining an audible tone and minimizing the tactile vibration the patient feels, which can sometimes be confused with sound. To begin the test, the clinician strikes the tuning fork to initiate a vibration, usually against a firm surface.
After activation, the base of the vibrating tuning fork is placed firmly on a central, midline point of the patient’s head. Common placement sites include the center of the forehead, the top of the head (vertex), or the bridge of the nose. These midline locations ensure that the bone-conducted sound waves are delivered equally to the cochlea of both ears through the skull. The patient reports where they perceive the sound: either in the middle of their head or louder in one ear than the other.
Understanding the Test Results
The fundamental concept in interpreting the Weber test is sound “lateralization,” which describes the patient’s perception of the sound being louder in one ear. The possible outcomes of the test fall into three distinct categories. A normal finding, or one consistent with symmetrical hearing loss, occurs when the patient reports hearing the sound equally in both ears, or perceiving it as coming from the middle of the head.
The other outcomes involve lateralization, where the sound is perceived as louder in the right or left ear. This asymmetrical perception of the bone-conducted sound indicates a possible hearing imbalance between the two ears. The direction of this lateralization—to the right or to the left—is recorded and used as a key piece of diagnostic evidence.
Differentiating Hearing Loss Types
The primary utility of the Weber test is its ability to distinguish between the two main categories of hearing loss: conductive and sensorineural. Conductive hearing loss is caused by a problem in the outer or middle ear that prevents sound from reaching the inner ear efficiently, such as fluid buildup or a perforated eardrum. Sensorineural hearing loss, conversely, is related to damage in the inner ear, specifically the cochlea, or the auditory nerve itself.
When the Weber test results lateralize, the pattern of sound perception provides a specific clue to the type of loss. In a unilateral conductive hearing loss, the sound will lateralize to the impaired ear. This is often explained by a masking effect: the conductive problem blocks environmental noise from reaching the inner ear, making the bone-conducted sound appear relatively louder in the affected ear because it is not competing with external sounds.
Conversely, in a unilateral sensorineural hearing loss, the sound lateralizes away from the impaired ear, meaning it is heard louder in the unaffected ear. This is because the damaged cochlea or nerve in the impaired ear is less capable of perceiving the sound stimulus, even when delivered by bone conduction. The Weber test is frequently performed in conjunction with the Rinne test, which compares air and bone conduction in a single ear, to confirm the type and location of any identified hearing impairment.