The Bing test is one of several well-known subjective hearing test procedures that use certain tuning fork tests to detect whether a unilateral sound conduction or sound perception disorder is present when hearing is diminished. The Bing test uses the difference in hearing sensation between bone and airborne sound when the external auditory canal is alternately closed and reopened.
What is the Bing test?
Like all tuning fork tests, the Bing test is relatively simple to perform. If a unilateral hearing loss is suspected, the Bing test can be used to identify whether there is a conductive or a sensorineural problem. The Bing test is usually performed using the Rydel and Seiffer tuning fork, which was designed specifically for tuning fork hearing tests and for neurological vibration tests. Like all tuning fork tests, the Bing test is relatively simple to perform. If a unilateral hearing loss is suspected, the Bing test can be used to identify whether there is a conductive or a sensorineural problem. The tuning fork is struck and the foot of the fork is held firmly on the bony process of the temporal bone behind the auricle (processus mastoideus) and the external auditory canal is alternately closed and opened again with the finger. If there is no change in the hearing sensation between the briefly closed and opened auditory canal, a conductive disorder is present. If the sound of the tuning fork is heard significantly louder when the ear canal is closed, a sound perception disorder is present in the ear concerned. Since normal-hearing persons experience the same qualitative effect at an overall higher volume level, the hearing ability must be tested before the Bing test, e.g. by means of a sound audiogram, in order to avoid misinterpretations. The Bing test was originally known as faux bing. When the foot of the vibrating tuning fork is placed on the center of the skull of a patient with a unilateral sound conduction disorder, the patient hears the sound louder in the disordered ear. If the normal-hearing ear is now additionally closed with the finger, the sound does not move to the other side to the “healthy” ear, whose ear canal is now closed with the finger, but the patient still hears the sound louder with the ear with sound conduction disturbance.
Function, effect and goals
When checking hearing disorders, it is not only a matter of how much the hearing sensation is reduced, but in terms of subsequent targeted therapy or technical support for hearing, the distinction between conductive and sensorineural disorders is enormously important. A sound conduction disorder is present when a link in the transmission chain in the “mechanical” part of the auditory organ, which includes the outer ear and the ossicles of the middle ear, exhibits functional disorders. A sound perception disorder is present when, in the “electrical” part of the hearing process, which includes the conversion of the mechanical sound waves into electrical nerve impulses in the inner ear, the transmission of the signals to the CNS, and the further processing of the signals in the CNS, one of the components has a functional disorder. A sound that reaches the ear mainly through the skull bone is called bone or structure-borne sound. Like sound transmitted through the air and external auditory canal, it causes the eardrum and ossicles to vibrate. In this case, however, part of the vibrational energy is reflected back outward by the eardrum, resulting in an overall attenuation of loudness. If the external auditory canal is closed, the part of the sound radiated from the eardrum into the auditory canal is reflected back onto the eardrum (in this case by the finger). The patient or subject now hears the sound transmitted by structure-borne sound much louder. The Bing test takes advantage of this phenomenon, also known as the occlusion effect. The Bing test is used in patients with unilateral hearing loss and provides clarity as to whether a sound conduction or sound perception disorder is present. Behind the auricle of the ear with the hearing loss, the foot of the struck tuning fork is held firmly on the bony process of the temporal bone (mastoid process) and the external auditory canal is closed and reopened several times with the finger.If the patient does not feel a difference in the loudness of the sound between the occluded and unoccluded phases of the ear canal, there is a sound perception disorder. The sound perception disorder can have several causes, either there is a disorder of the sensory cells in the cochlea in the inner ear, so that the mechanically arriving sound is not properly translated into electrical nerve impulses, or the transmission line, the auditory nerve (vestibulocochlear nerve), has a disorder, or the signals cannot be properly processed in the brain into corresponding auditory impressions.
Risks, side effects, and dangers
All known tuning fork procedures for testing hearing – including the Bing test – are performed non-invasively and completely free of chemicals or drugs. In addition, the Bing test causes no pain and is free of side effects. There are no known risks or dangers. The results of the Bing test, which are rather qualitative due to their subjectivity, can be supplemented by an objective procedure with quantitatively comparable values. These are impedance measurements of the eardrum. The most important procedure is tympanometry, in which the external auditory canal is closed and a test tone is emitted into the auditory canal. The reflection of the eardrum is then measured at different pitches, intensities and at different pressures in the external auditory canal from slight overpressure to slight underpressure. In this way, the different values between body sound and airborne sound can also be quantitatively evaluated. It remains to be stated that the subjective Bing test, as well as the other tuning fork tests, can provide important qualitative information about the presence of a sound conduction or a sound perception disorder, but that further objective diagnostic procedures with quantifiable parameters are recommended in case of positive findings.
