AUDIOGRAMS
What is an audiogram?
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shaded region shows the level and |
An audiogram is a graph that shows the softest sounds a person can hear at different pitches or frequencies. An “O” often is used to represent responses for the right ear and an “X” is used to represent responses for the left ear. There usually is a key on the audiogram; similar to one found on a map, that identifies what the different symbols mean. The closer the marks are to the top of the graph, the softer the sounds that can be heard. The audiogram shown above on the left indicates the different degrees of hearing loss.
The pitches shown on the audiogram are those most important for hearing and understanding conversation. Each sound we hear when someone speaks has a different pitch and loudness. For example, the “s” sound is high in pitch and quiet. The “o” sound is low in pitch and louder. The audiogram shown above on the right has a shaded area that shows the range of pitch and loudness for most speech sounds.
During a hearing test, sounds are presented in different ways. When testing with earphones or loudspeakers, the sounds go into the ear canal, through the middle ear to reach the inner ear. This is known as air conduction testing. Air conduction testing looks at how the whole hearing system responds to sound.
If air conduction testing shows a hearing loss, another device called a bone
vibrator is placed behind the ear to send sounds directly to the inner ear.
Sounds are sent through the bones of the head and do not pass through the
eardrum or the middle ear. This is called bone conduction testing.
When something stops sounds from moving through the eardrum and middle ear,
bone conduction hearing levels will be better than air conduction levels.
This means a conductive hearing loss is present. When sound moves normally
through the outer and middle ear, but the inner ear does not work normally,
both bone conduction and air conduction hearing levels will be the same. A
sensorineural hearing loss is present.
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The audiogram here shows a severe hearing loss. A child with this hearing loss may only hear very loud speech or loud environmental sounds, such as a fire truck siren or a door slamming.
Click for an
example of severe hearing loss
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The audiogram here shows a moderate high-pitched hearing loss. A child with this hearing loss will have difficulty hearing regular speech, even at close distances.
Click for an
example of moderate hearing loss
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This audiogram shows a mild high-pitched hearing loss. A child with this hearing loss will have trouble hearing and understanding soft speech, speech from a distance or speech in a background of noise.
Click for an
example of mild hearing loss
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You can experience what hearing loss sounds like compared to normal hearing. The audiogram to the right shows normal hearing.
Click for an
example of normal hearing
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An audiogram is a chart that displays information about a person's hearing abilities. A person's hearing is tested by an audiologist and then plotted onto a chart which has the loudness of the sound, measured in decibels (dB), shown vertically on the left side and the frequency or pitch of the sound across the top, measured in Hertz (Hz). The dB are listed from top to bottom starting with 0 and usually stops at 120 dB. The frequency starts on the left side with 125 cycles per second (Hz) and goes up to 8000 cycles per second (Hz).
How to interpret an audiogram:
A person can be tested two different ways and both ways can be plotted on the audiogram. One testing method is Pure Tone Testing and the other is Bone Conduction. Pure tone testing, also called the air conduction test, uses headphones in which tones are sounded off in each of the ears. The child or person is then instructed to raise either a right or left hand depending on which ear the sound was in. The audiologist then plots the information for each ear onto a graph. The left ear is marked by an "X" and the right ear is marked by an "O."
Bone conduction testing occurs by directly stimulating the inner ear and bypassing the outer and middle ear altogether. A little microphone is placed behind the ear and the sound enters the skull through the mastoid bone. The test is conducted with the raising of the hands when a sound is heard. This test is plotted on the graph using triangular brackets. This bracket '<' is for the right ear, and this one '>' is for the left ear.
When both tests have been completed and plotted onto the chart, the person's hearing or loss of hearing can be identified. The chart shows the different decibel losses for each ear and at which frequencies. The person's loss is usually stated in terms of the one type of loss to another. For example: a mild to moderate loss or a moderate to profound loss.
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Examples of Audiograms:
Example 1:
The following is an example of an audiogram of a child who has a mild to moderate hearing loss in both ears:
41 to 55 db (mild loss)
Effects On Understanding Language and Speech:
· Understands conversational speech at a distance of 3 to 5 feet (face to face) · May miss as much as 50% of class discussions if voices are faint or not in line of vision · May have limited vocabulary and speech irregularities
Probable Educational Needs and Programs:
· Should be referred for special education evaluation and educational follow- up · May benefit from individual hearing aid and training in its use · Favorable seating and possible special education supports, especially for primary-age children · Attention to vocabulary and reading · May need speechreading instruction · Speech conversation and correction, if indicated.
Example 2:
The following example is of a child who has a moderate to severe hearing loss:
Source: Exceptional Children: An Introduction to Special Education (fifth edition) William L. Heward, Prentice-Hall, Inc. 1996
71 to 90 db (severe loss)
Effects On Understanding Language and Speech:
· May hear loud voices about 1 foot from the ear · May be able to identify environmental sounds · May be able to discriminate vowels but not all consonants · Speech and language likely to be impaired or to deteriorate · Speech and language unlikely to develop spontaneously if loss is present before 1 year of age
Probable Educational Needs and Programs:
· Likely to need a special education program for hearing-impaired children, with emphasis on all language skills, concept development, speechreading, and speech · Needs specialized program supervision and comprehensive supporting services · Can benefit from individual hearing evaluation · Auditory training on individual hearing evaluation · Part-time regular class placement as profitable for students
