Pure Tone Audiometry
Purpose
The sounds used to test a person's hearing must be clearly specified so that the thresholds are both accurate and repeatable. The test sounds used to determine the degree of hearing loss are usually pure tones of different frequencies.
Materials
Audiometer
The principle tool used in the process of evaluating a patient's auditory functioning is the audiometer, an electronic device that produces and delivers sounds to the patient. The pure-tone audiometer must be able to produce pure tones at certain frequencies, precisely control the levels of these tones, and deliver them to the patient in the manner intended by the audiologist.
Air-Conduction Testing
Air-conduction testing usually involves presenting the test signals from standard audiometric (supra-aural) earphones. Insert earphones can also be used for air-conduction testing. Insert earphones go into the ear canals instead of being worn over the ears. They are useful when facing several problem situations, but the convenience of standard earphones makes them the method of choice under routine conditions.
Bone-Conduction Testing
Bone-conduction is tested by applying a vibratory stimulus to the skull, which is transmitted to the cochlea and heard as sound. To do this, a bone conduction vibrator is placed on the mastoid process or forehead and is held in place by a spring headband. Even though a mastoid versus forehead placement of the bone vibrator is an arguable issue, mastoid placement is recommended here and is the more commonly used method.
Procedures/Instruction
Earrings and most eyeglasses must be removed for both comfort and proper fitting of the earphones. It is also necessary to remove any other objects that could interfere with the placement of the headset. Hearing aids should be removed, turned off, and put away during the test. Chewing gum and candy must be disposed of. The audiologist should check to see whether putting pressure on the external ear seems to cause the ear canal to close. This is important because the pressure exerted by the earphones might similarly cause collapse of the ear canals and give the false impression of a conductive hearing loss. finally, the clinician gently places the headset on the patient, being careful that the earphone receivers are located over the entrances to the ear canals. It is not desirable to allow the patient to apply the headset because the fit may not be optimal. If the patient is allowed to do this, then the clinician must check the fit and make any necessary adjustments.
Interpretation/Site of Lesion
Pure Tone Average in dB HL<15
16-25 26-40 41-55 56-70 71-90 > or = 90 |
Degree of Hearing LossNormal Hearing
Slight Hearing Loss Mild Hearing loss Moderate Hearing Loss Moderately Severe Hearing Loss Severe Hearing Loss Profound Hearing Loss |
Audiogram Examples
Management
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