Audiometry
What is Audiometry?
Audiometry is essential test for tinnitus patients. In patients who suffer from Meniere's disease hearing loss is one of the basic criteria. For vertigo or dizziness sufferers it is important to identify any ear disease.
Audiometry Testing
The testing of hearing ability shows parameters of symmetry versus asymmetry, air conduction versus bone conduction, speech recognition in every ear and the dynamic of hearing level over time.
Sometimes it is possible to find improvement: in patients after acute acoustic trauma, treated ear infection, stapedectomy in otosclerosis sufferers or patients with Meniere's disease who received effective treatment for decreasing the amount of fluids in their internal ear.
Audiometry tests
Audiometric tests are commonly used to diagnose the patient's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguished speech from background noise.
Audiometry can do two more tests: (I) Acoustic reflex. (II) Otoacoustic emissions.
On the basis of audiometric tests the clinicians can diagnose hearing loss or some diseases of the ear.
Hearing test
The use of an audiogram is important part, but not the only parameter.
Threshold of audibility
The basic parameter for the assessment of hearing is the determination of the threshold of audibility. It means: the minimal level of sound required to be just audible.
Noise hazards
This parameter may vary for the same patient within a range of up to 5 dB from test to test, but it is an additional and useful tool in the follow up of the potential noise hazards due to exposure to noise.
Medical history
The first stage in the hearing test is to obtain information about the patient's past medical history.
It means that in addition to the auditory aspects, also other health conditions, which may be relevant to hearing loss detected by an audiometric test.
Hearing loss
The common location of the hearing loss is bilateral. Variations in every ear are possible finding in many patients.
Wax in the external ear canal can also cause a pseudo hearing loss, so the ear should be examined to see if the tympanic membrane can be observed. Today, it is recommended to do it under the guidance of a microscope and not rinsing by a syringe.
Press for further reading about hearing loss
Otoscopy
Otoscopy is done before the audiometry in order to diagnose the physical status of the tympanic membrane: mechanical damage which may reduce the ability of sound to be transported to the cochlea, infection or scars.
Audiometery test procedure
Automatic/manual audiometers
The audiologist can do the hearing test by automatic or manual audiometers.
Principles
The principles of the procedure are the same: (I) the patient is asked to remove any personal object such as spectacles, earrings or hearing devices. (II) The tester tells the patient about the procedure. (III) The patient is asked to respond to the auditory stimuli by yes or no (usually via a special button).
High quality earphones
The high quality earphones are fitted over the ears and the test is then carried out on every ear. The presentation of sound to the ears starts with a threshold test.
Stimulation
The audiologist stimulates every by a sound of pure tone at a frequency of 1 kHz at varying levels of energy ranging from low to high and high to low. The protocol includes repetition of the stimuli several times in order to calculate the mean threshold of that specific patient and his performance in the test.
Final threshold
A final threshold check should be performed after the hearing test is over.
Deviation from the basic threshold indicates that an unnoticed error contaminated the test. The maximal difference allowed between both threshold checks should be 10 dB or less.
In a case that it exceeds the 10 dB, it is a reason to perform a re-test.
Hearing test accuracy
The accuracy of a hearing test can be affected by 4 main factors:
1. Technical limitations
The best precision that the frequency or the hearing level be determined with the current technology.
2. Learning effect
The patient is using the test of his first ear as a learning experience that helps to improve his performance in detecting the threshold. The result is a better performance in the second time, and a false conclusion that the second ear is better.
3. Headphone fit
Differences in the position of the headphones may be responsible to variability in the detection of the threshold.
4. Background noise
Environmental noises may influence the results of the hearing tests. In home made systems the test is done in a room that is not a professional sound-proof chamber. Such circumstances involve acoustic contamination by external sounds that influence the test.
Audiometric testing - another source of error
Reliability of the patient
Another source of error in audiometric testing is that it is subjective and depends on the reliability of the patient.
In other words: demented patients, aggravates, psychologically disturbed patients, seekers of compensation from insurance companies (consciously or unconsciously) and patients who have a secondary gain (soldiers who does not want to be in their army unit) are examples of the part of the patient cooperation in the audiometric test.
Cooperation with the hearing test
If the patient is unable or unwilling to cooperate with the hearing test then false diagnosis may be found. The protocol, which is described above, enable to compare the threshold of hearing of the individual undergoing a hearing test with a reference value at a range of octave band frequencies.
From this data a graphical representation creates the audiogram of a specific patient with normal hearing or hearing loss at various frequencies, symmetric or asymmetric.
Tinnitus patients
The audiometer can be serve tinnitus patients in two more ways:
1. Identify tinnitus frequency and level
the procedure of matching can help to identify the frequency (Hz) and level (Decibels) of the tinnitus when compared to the sound that is presented via earphones of the audiometer.
2. Check tinnitus maskability
The audiologist can use the audiometer in order to check the maskability of the tinnitus by stimulating the ears with various sounds. Audiometry is very basic test in the management of tinnitus, vertigo, dizziness and meniere's disease.
Press for further reading about Tinnitus and Tinnitus Curative Treatment
