170 Chapter 9
damage to the hearing mechanism as a result of noise exposure, toxins, disease, hypertension, and
several other factors. For some persons, tinnitus is a minor nuisance; for others, it can be a major
disability significantly affecting the quality of life. Unfortunately, although there are several medi-
cal and behavioral treatments for tinnitus, little can be done to eliminate it. Carpenter- Thompson,
McAuley, and Husain (2015) found that active people reported lower levels of tinnitus with higher
levels of activity.
Audiograms and Types of Hearing Loss
Audiograms are graphic repre sen ta tions of hearing test results. They provide a visual depiction
of the person’s hearing thresholds and serve as a basis for interpreting audiometric results. The test
frequencies are listed in hertz (Hz) along the top and the patient’s hearing level in decibels (dB)
down the left side. Air conduction test results are plotted at the intersection of the frequency and
decibel lines using O markings for the right ear and X markings for the left ear. In bone conduction
test results, “<” represents the right ear and “>” the left one. Bone conduction bypasses the external
and middle ears and transmits sound through the bones of the head. Because of cross- hearing,
sometimes it is necessary to perform masking, that is, to introduce a competing sound during the
test. Masked symbols are “[” and “]” for the right and left ears, respectively.
Figure 9-2 pres ents an audiogram of a binaural conductive hearing loss. It shows similar
depressed pure tone air conduction thresholds in the 30- to 40- dB range with no discernible
slope. Bone conduction testing reveals normal thresholds. Together, air and bone conduction
results depict a typical air– bone gap. This audiogram shows the patient’s ability to hear better
through bone conduction than air conduction, indicating that the lesion is located in the exter-
nal or middle ear.
Figure 9-3 shows a binaural sensorineural hearing loss. In this audiogram, bone and air con-
duction thresholds are depressed in both ears, with gradually decreasing hearing sensitivity in the
2000- , 4000- , and 8000- Hz ranges. In mixed hearing loss, bone conduction thresholds are also
depressed.
Figure 9-2. Binaural conductive hearing loss.