Tuning Fork Tests
Purpose
Tuning forks were used to test hearing long before the development of the audiometer. Four of the more well known of these tests are the Schwabach, Weber, Boing and Rinne tests. All are still used and can also be done audiometrically
Materials: Set of Tuning Forks
Procedures/Instruction
Schwabach Test
The Schwabach Test is a technique for estimating a patient's hearing sensitivity by bone-conduction. The frequency of the tuning fork used for this test is chosen based on the frequency at which hearing loss is suspected. The tuning fork is struck and placed on the mastoid of the patient. The patient informs the clinician when the tone is no longer heard. The clinician then places the fork on his or her own mastoid process to determine the presence of the tone. If the tone is still present, the clinician determines how long he or she perceives the tone beyond that of the patient. To correlate the findings of this test with the pure-tone audiogram, the clinician must know the decay rate of the tuning fork in use. If the tone decays at a rate of 5dB per second and the clinician has perceived the tone for 6 seconds longer than the patient, it can be determined that the patient has a 30dB HL hearing loss, assuming that the audiometric thresholds for the clinician are at 0 dB HL.
There are three basic outcomes to the test, assuming the examiner has normal hearing. First, the patient could have normal hearing by bone conduction. Second, the patient could hear the tone longer than the examiner indicating a conductive hearing loss. Finally, the patient could have a sensorineural hearing loss if he or she hears the tone for a shorter time period than the examiner. The Shwabach test is rarely used to identify hearing loss due to the wide availability of clinical audiometers. Results from the test should be interpreted with caution.
There are three basic outcomes to the test, assuming the examiner has normal hearing. First, the patient could have normal hearing by bone conduction. Second, the patient could hear the tone longer than the examiner indicating a conductive hearing loss. Finally, the patient could have a sensorineural hearing loss if he or she hears the tone for a shorter time period than the examiner. The Shwabach test is rarely used to identify hearing loss due to the wide availability of clinical audiometers. Results from the test should be interpreted with caution.
Weber Test
The Weber test is used to determine the presence of a conductive component in the case of unilateral hearing loss. The test is based on both the occlusion effect and the Stenger effect. For this test, a low-frequency tuning fork is struck, and the base is placed on the forehead or frontal sinuses. The patient is instructed to tell the examiner in which ear the tone is heard. It is important to instruct the patient that he or she might hear the tone in the better ear, the worse ear, or possibly somewhere else in the head.
For patients who have a conductive hearing loss in one ear, an occlusion effect is created in that ear, causing a higher sensation level. When the tuning fork is placed onto the forehead, a tone of the same intensity and phase is presented to both ears simultaneously. Due to the Stenger effect, the patient hears the tone only in the ear with the higher sensation level. Because the occlusion effect creates a higher sensation level, the patient reports hearing the sound in the ear with the conductive hearing loss.
For patients who have a sensorineural hearing loss in one ear, there is no occlusion effect. The patient has a higher sensation level in the opposite ear and will report hearing the sound in that ear, again due to the Stenger effect. Another way to say this is that the tone will localize to the ear with the conductive component or to the ear with the better sensorineural reserve. In some cases, patients are unable to differentiate in which ear the sound was heard, and the test outcome is equivocal.
Finally, patients with normal hearing, as well as some with bilateral sensorineural hearing loss, may report hearing the tone in both ears or "all over" the head.
For patients who have a conductive hearing loss in one ear, an occlusion effect is created in that ear, causing a higher sensation level. When the tuning fork is placed onto the forehead, a tone of the same intensity and phase is presented to both ears simultaneously. Due to the Stenger effect, the patient hears the tone only in the ear with the higher sensation level. Because the occlusion effect creates a higher sensation level, the patient reports hearing the sound in the ear with the conductive hearing loss.
For patients who have a sensorineural hearing loss in one ear, there is no occlusion effect. The patient has a higher sensation level in the opposite ear and will report hearing the sound in that ear, again due to the Stenger effect. Another way to say this is that the tone will localize to the ear with the conductive component or to the ear with the better sensorineural reserve. In some cases, patients are unable to differentiate in which ear the sound was heard, and the test outcome is equivocal.
Finally, patients with normal hearing, as well as some with bilateral sensorineural hearing loss, may report hearing the tone in both ears or "all over" the head.
Bing Test
the Bing test is based on the occlusion effect. In the case of normal hearing or sensorineural loss, the patient will perceive a bone-conducted signal as louder when the ear canal is closed versus open due to the occlusion effect. If there is a conductive loss where the breakdown in function causes an occlusion effect in either or both ears, no difference will be detected between open versus closed ear canal conditions because the disorder itself is already causing an occlusion effect.
To perform the test, instruct the patient that you will place the tuning fork behind her or his ear on the mastoid process. Tell the patient that after the tuning fork is on the mastoid, the patient should indicate whether he or she hears a tone. Then, the patient must tell you when the tone has "stopped" or is no longer perceived. When the patient indicates that he or she no longer perceives the tone, gently close the opening to the ear canal. ask the patient to inform you if the sound is heard again, in either ear. Alternatively, the base of the vibrating tuning fork can be placed on the patient's mastoid process while the clinician presses the tragus down to occlude the ear canal opening as the tines are vibrating. In this case, the patient makes the subjective indication whether the tone is "louder" when the ear canal is closed versus open.
A positive Bing test result occurs if the patient perceives the tone again or louder when the ear canal is occluded. In this case, it is likely that there is no conductive component because the patient does not perceive the tone again, or perceives no difference, with the ear canal occluded. In this case, there is likely a conductive hearing loss because the disordered middle ear system was already resulting in an occlusion effect prior to manual occlusion of the ear canal.
To perform the test, instruct the patient that you will place the tuning fork behind her or his ear on the mastoid process. Tell the patient that after the tuning fork is on the mastoid, the patient should indicate whether he or she hears a tone. Then, the patient must tell you when the tone has "stopped" or is no longer perceived. When the patient indicates that he or she no longer perceives the tone, gently close the opening to the ear canal. ask the patient to inform you if the sound is heard again, in either ear. Alternatively, the base of the vibrating tuning fork can be placed on the patient's mastoid process while the clinician presses the tragus down to occlude the ear canal opening as the tines are vibrating. In this case, the patient makes the subjective indication whether the tone is "louder" when the ear canal is closed versus open.
A positive Bing test result occurs if the patient perceives the tone again or louder when the ear canal is occluded. In this case, it is likely that there is no conductive component because the patient does not perceive the tone again, or perceives no difference, with the ear canal occluded. In this case, there is likely a conductive hearing loss because the disordered middle ear system was already resulting in an occlusion effect prior to manual occlusion of the ear canal.
Rinne Test
The Rinne test is useful for differentiating between normal hearing or sensorineural loss and conductive hearing loss. In patients with normal middle ear function and normal hearing sensitivity or sensorineural hearing loss, the patient will perceive a bone-conducted signal as softer than the same air-conducted signal as softer than the same air-conducted signal as softer than the same air-conducted signal from the tuning fork. This is because air conduction is more efficient than bone conduction. In the case of a conductive hearing loss, the patient will perceive the bone-conducted signal as louder because the pathology causing the hearing loss has created a less efficient system for transmission of the air-conducted signal.
To perform the test, strike a low-frequency tuning fork and place it about 2 inches from the ear canal of the patient. Ask the patient if the tone is perceived by instructing the patient to, "Raise your hand as long as you hear the tone." When the patient's hand is lowered, place the base of the tuning fork on the mastoid process of the patient. Ask the patient, "Do you hear the tone again?" If the tone returns, the test is considered a negative Rinne result, indicating a conductive component. If the tone is no longer present, the test is considered a positive Rinne result. This is consistent with the absence of a conductive hearing loss. Another method for performing this test is to hold the tuning fork near the ear canal for a given period of time and then move the fork to the mastoid process. In this case, the patient should respond by indicating in which case the tone was louder. If the tone is reported as louder while the tuning fork is held near the ear canal, this is a positive Rinne because the signal should be more efficiently perceived via air conduction. This condition is consistent with either normal hearing sensitivity or a sensorineural hearing loss. If the tone is reported as louder while the tuning fork is placed on the mastoid, this a negative Rinne result because the occlusion effect caused by the pathology is causing the signal to be perceived more efficiently via bone conduction.
To perform the test, strike a low-frequency tuning fork and place it about 2 inches from the ear canal of the patient. Ask the patient if the tone is perceived by instructing the patient to, "Raise your hand as long as you hear the tone." When the patient's hand is lowered, place the base of the tuning fork on the mastoid process of the patient. Ask the patient, "Do you hear the tone again?" If the tone returns, the test is considered a negative Rinne result, indicating a conductive component. If the tone is no longer present, the test is considered a positive Rinne result. This is consistent with the absence of a conductive hearing loss. Another method for performing this test is to hold the tuning fork near the ear canal for a given period of time and then move the fork to the mastoid process. In this case, the patient should respond by indicating in which case the tone was louder. If the tone is reported as louder while the tuning fork is held near the ear canal, this is a positive Rinne because the signal should be more efficiently perceived via air conduction. This condition is consistent with either normal hearing sensitivity or a sensorineural hearing loss. If the tone is reported as louder while the tuning fork is placed on the mastoid, this a negative Rinne result because the occlusion effect caused by the pathology is causing the signal to be perceived more efficiently via bone conduction.
Interpretation/Site of lesion
TestWeber
Bing Rinne |
OutcomeSound lateralized to midline of both ears equally
Better Ear Poorer Ear Positive (occluded louder) Negative (no difference) Positive (Air > Bone) Negative (Bone > Air) |
Site of LesionNormal (or sensorineural loss)
Sensorineural loss Conductive loss Normal or sensorineural loss Conductive loss Normal or sensorineural loss Conductive loss |
Management
References/Works Cited
Gelfand, Stanley A. Essentials of Audiology. Thieme, 2016.
DeRuiter, Mark, and Virginia Ramachandran. Basic Audiometry Learning Manual. Plural Publishing Inc., 2017
DeRuiter, Mark, and Virginia Ramachandran. Basic Audiometry Learning Manual. Plural Publishing Inc., 2017