Procedure Bhearing Tests

Perform the following tests in a quiet room, using your laboratory partner as the test subject.

1. Auditory acuity test. To conduct this test, follow these steps:

a. Have the test subject sit with eyes closed.

b. Pack one of the subject's ears with cotton.

c. Hold a ticking watch close to the open ear and slowly move it straight out and away from the ear.

d. Have the subject indicate when the sound of the ticking can no longer be heard.

e. Use a meter stick to measure the distance in centimeters from the ear to the position of the watch.

f. Repeat this procedure to test the acuity of the other ear.

g. Record the test results in Part C of the laboratory report.

2. Sound localization test. To conduct this test, follow these steps:

a. Have the subject sit with eyes closed.

Hold the ticking watch somewhere within the audible range of the subject's ears and ask the subject to point to the watch. Move the watch to another position and repeat the request. In this manner, determine how accurately the subject can locate the watch when it is in each of the following positions: in front of the head, behind the head, above the b.

Human Anatomy Behind Ears

head, on the right side of the head, and on the left side of the head. d. Record the test results in Part C of the laboratory report.

3. Rinne test. This test is done to assess possible conduction deafness by comparing bone and air conduction. To conduct this test, follow these steps:

a. Obtain a tuning fork and strike it with a rubber hammer, or on the heel of your hand, causing it to vibrate.

b. Place the end of the fork's handle against the subject's mastoid process behind one ear. Have the prongs of the fork pointed downward and away from the ear, and be sure nothing is touching them. (See fig. 33.5a.) The sound sensation is that of bone conduction. If no sound is experienced, nerve deafness exists.

c. Ask the subject to indicate when the sound is no longer heard.

d. Then quickly remove the fork from the mastoid process and position it in the air close to the opening of the nearby external auditory meatus. (See fig. 33.5b.)

If hearing is normal, the sound (from air conduction) will be heard again; if there is conductive impairment, the sound will not be heard. Conductive impairment involves outer or middle ear defects. Hearing aids can improve hearing for conductive deafness because bone conduction transmits the sound into the inner ear. Surgery could possibly correct this type of defect.

e. Record the test results in Part C of the laboratory report.

4. Weber test. This test is used to distinguish possible conduction or sensory deafness. To conduct this test, follow these steps:

a. Strike the tuning fork with the rubber hammer.

b. Place the handle of the fork against the subject's forehead in the midline. (See fig. 33.6.)

c. Ask the subject to indicate if the sound is louder in one ear than in the other or if it is equally loud in both ears.

If hearing is normal, the sound will be equally loud in both ears. If there is conductive impairment, the sound will appear louder in the affected ear. If some degree of sensory (nerve)

Figure 33.5 Rinne test: (a) first placement of vibrating tuning fork until sound is no longer heard; (b) second placement of tuning fork to assess air conduction.

Figure 33.5 Rinne test: (a) first placement of vibrating tuning fork until sound is no longer heard; (b) second placement of tuning fork to assess air conduction.

Rinnes And Weber Test

Figure 33.6 Weber test.

Ear Images For Anatomy Test

deafness exists, the sound will be louder in the normal ear. The impairment involves the organ of Corti or the cochlear nerve. Hearing aids will not improve sensory deafness. d. Have the subject experience the effects of conductive impairment by packing one ear with cotton and repeating the Weber test. Usually the sound appears louder in the plugged (or impaired) ear because extraneous sounds from the room are blocked out. e. Record the test results in Part C of the laboratory report.

5. Complete Part C of the laboratory report.

Critical Thinking Application

| Ear structures from the outer ear into the inner ear are progressively smaller. Using results obtained from the hearing tests, explain this advantage.

Web Quest

What are the causes of hearing impairment? Search this site and review the anatomy and physiology of the ear at http://www.mhhe.com/biosci/abio/martinlmwq.mhtml

DEMONSTRATION

a sk the laboratory instructor to demonstrate the use of the audiometer. This instrument produces sound vibrations of known frequencies that are transmitted to one or both ears of a test subject through earphones. The audiometer can be used to determine the threshold of hearing for different sound frequencies, and, in the case of hearing impairment, it can be used to determine the percentage of hearing loss for each frequency.

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