Hearing test
From Free net encyclopedia
A hearing test is an evaluation of the sensitivity of a person's sense of hearing, most often performed by an audiologist using an audiometer. Audiologists are the only health professionals with extensive training on the anatomy and physiology of hearing, and are the only health professionals certified to perform diagnostic hearing tests. It is used to determine a person's hearing sensitivity at different frequencies.
A hearing test is usually administered to a person by having them sit in a soundproof booth with a set of headphones over the ears or small foam insert earphones placed in the ears, which is connected to an audiometer. The audiometer produces tones at specific frequencies and set levels to each ear independently. The audiologist plots the loudness (in decibels) on an audiogram. The person having their hearing tested will convey that they have heard the tone by either raising their hand or pressing a button. As the test progresses, the audiologist plots points on a graph where the frequency is on the x-axis and the loudness on the y-axis. Once each frequency of normal hearing ability is tested and plotted the points are joined by a line so that one can see at a glance the frequencies a person is not hearing normally and to what degree the hearing loss is. Normal hearing at any frequency is defined as 0dB, with worsening hearing the number increases. Hearing levels above around 40 dB are pathological.
Hearing tests are often conducted at workplaces as part of health and safety initiatives.
A complete hearing evaluation involves several other tests as well. In order to determine what kind of hearing loss is present, a bone conduction hearing test is administered. In this test, a small vibrator is placed behind the ear or on the forehead. The vibrator vibrates at specific frequencies, and the person being tested hears tones or beeps just like in the test with earphones. This test helps the audiologist determine whether the hearing loss is conductive (caused by problems in the outer or middle ear) or sensorineural (caused by problems in the cochlea, the sensory organ of hearing). The audiologist will also conduct speech tests, whereby the patient repeats the words he or she hears. In addition, a test called a tympanogram is generally done. In this test, a small probe is placed in the ear and the air pressure in the ear canal is varied. This test tells the audiologist how well the ear drum and other structures in the outer and middle ear are working. The last test the audiologist performs is an acoustic reflex test. In this test a probe is placed in the ear and a loud (greater than 70 dB) tone is produced. The test measures the reflexive contraction of the stapedius muscle, which is important in protecting the ear from loud noises.