Audiograms, what are they and how do you read them.
By: Caitlin Farnsworth, Chelsea Woodard, Julianna Reed
What to expect for your hearing test Be prepared to give a brief medical history
regarding your hearing Your audiologist will ask you a few questions regarding your hearing
past and possible exposure to loud noises.
The test is non-invasive- so sit back and relax, there is nothing to be worried about.
You will then be placed in a sound-treated room or both- to prevent background noises
such as air conditioners, or the office environment from distracting you from the test.
Headphones will be placed on your head- these are where you will hear the instructions from
the audiologist and the sounds for the test.
You will be asked to listen to different sounds and told to acknowledge the sound either by
raising a hand or pressing a button.
this may vary depending on what the audiologist prefers.
Your results will then be plotted on an audiogram and interpreted and explained to you by your
audiologist.
See, wasn't that easy?
What is an audiogram?
An audiogram is a graphical display of a hearing test.
So if we take a look at the picture to the right, you will see and audiologist performing
a hearing test.
And what she's doing is determining the softest sounds that you can hear at each specific
frequency.
And these sounds and your results are graphed on to the image to the left which is the audiogram.
In this next section, we will be going over Audiometric testing.
This will include definitions of air conduction testing and bone conduction testing.
During a hearing test sounds are presented in different ways.
They can be done with a bone conduction or air conduction testing.
So, when testing with ear phones or loud speakers, the sounds goes into the ear canal, through
the middle ear to reach the inner ear.
And this is known as air conduction testing.
So, air conduction testing looks at how the whole hearing system responds to sound.
And in this slide here, you can see a pretty cool example of how the sound is transmitted
into the ear.
The bone conduction is in orange and the air conduction is in blue.
Air conduction testing uses earphones or loud speakers and a sound proof room.
These send sounds to the ear canal through the middle ear to reach the inner ear.
So, this, what this does is evaluate the whole ear system.
The outer, the middle and the inner ear.
If air conduction testing shows a hearing loss, then another device called a bone vibrator
is placed behind the ear to send sounds directly to the inner ear.
And this is called a bone conduction test.
In bone conduction testing shown at the right a bone vibrator is placed behind the ear to
deliver the sound vibrations to the cochlea which is the hearing organ of the inner ear.
This allows the examiner to bypass the entire outside and middle ear areas and test the
sensitivity of the inner ear directly.
So.
These sounds are sent through the bones of the head and do not pass through the ear drum
or the middle ear.
The next section is going to be going over the different parts of an audiogram.
This is going to include terms used, symbols that are on the audiogram, definitions of
intensity and frequency and a description of the speech banana.
On this slide, you will see some terms that may be familiar to you or may be used by your
audiologist.
Hertz is a measurement of frequency.
This means the number of times a waveform will complete itself per second.
Decibels is a measurement of intensity.
This is the unit used to measure the intensity of a sound, by comparing it to a level on
a logarithmic scale Masked is when threshold was obtained with
noise in the opposite ear.
So, the interference of the ability to hear one sound, which would be the signal because
of the presence of another sound, which is the masker.
A sound is presented to the opposite ear being tested, to make sure you are properly testing
the ear to which the pure tone is being presented.
Unmasked is when no other noise is present to obtain threshold.
When a sound in presented alone, without any other noise or noises, this is unmasked, or
in other words "in quiet."
Threshold is the lowest intensity of sound needed to detect it's presence.
The faintest sound level that induces a response from a neuron is a threshold.
Pure Tone is the sound that has simple harmonic motion.
The sounds associated with simple harmonic motion, or a single frequency.
These symbols represent what may be seen on your audiogram results.
As seen in the example of the audiogram depicted here, there will be two colors, red and blue.
The red symbols will correlate to the right ear and the blue symbols will correlate to
the left ear.
Depending upon your results, some or all of the symbols you see here may be present on
your audiogram.
The first symbols of the list represent the air conduction threshold for either the right
ear or left ear, depending on the color.
The second symbols represent the bone conduction threshold for either ear
The funny looking symbols for "no response given" are actually downward facing arrows,
added to the symbols used for either air conduction or bone conduction and for either the right
or the left ear.
The next symbols listed are used to show the air conduction masking for each ear
The final symbols listed are to show the bone conduction testing, masked for each ear.
Intensity is measured in decibels.
And is listed on the vertical axis of the audiogram. It begins at zero decibels. This represents as very soft sound and it progresses
with each horizontal line below representing a successively louder sound.
0 decibels does not mean there that there is no sound at all.
Rather, it is the softest sound that a person with "normal" hearing ability would be
able to detect at least 50% of the time. There are some audiograms that begin at negative ten decibels or lower. So yours may depend on what you audiologist prefers to use.
Audiologists consider 0 -15 dB HL to be "normal hearing" in children and 0-25 decibels normal hearing in adults.
Just like a pianos keys, the frequencies are low on the left side ranging from 125 to 250
Hz and then gradually climb to higher frequencies on the right side.
The most important sounds for speech fall into the 250-6000 Hertz range.
The vowel sounds of speech are typically low frequency sounds that make up the loudness
of speech.
The consonant sounds like "f", "s" and "th" are high frequency sounds.
The speech banana.
When phonemes, or also known as sounds of human speech are plotted on the audiogram
they make up an area that looks like a banana.
This area is called the "Speech Banana" by audiologists and speech-language pathologists.
Depending on the severity of hearing loss, some or all sounds of speech may be unrecognizable
to a person with hearing loss.
On this photo here, you can see that there are small pictures of familiar, environmental
sounds shown on this audiogram at their respective frequency and intensity levels.
This can be helpful to keep in mind when trying to have a conversation with a person who has
hearing loss.
If they are unable to hear certain sounds that are produced at a lower frequency, it
may be helpful to omit any words that have those sounds in them, and use other words
instead.
As you can see in the photo, the higher the frequency and the louder the sound, more severe
the hearing loss.
For example, if a person was unable to hear the sound of a helicopter or an airplane,
they would probably have a profound hearing loss.
In the following slides, we will be discussing the different degrees of hearing loss.
Mild, mild to moderate, moderate, severe and profound hearing loss.
In order for an audiologist to determine the degree of hearing loss, they need to find
a pure tone threshold.
As mentioned earlier, the audiogram is a graph of hearing sensitivity and your hearing sensitivity
is measured by an audiologist by finding a pure tone threshold.
And this is done by instructing the patient that they will hear tones and some are going
to be very soft.
The patient is to press a button or raise their hand, every time they hear the tone.
Audiologists follow a down ten, up five rule which says that if the patient responds they
decrease the sound 10dB.
If the patient does not respond, they increase it 5 dB.
They follow this pattern until two out of three responses are obtained at the same level
on the ascending run.
This graph depicts a blank audiogram, and shows the various degrees of hearing loss
by colors.
As you can see, the yellow bar represents the range of normal hearing at the top of
the photo.
From there, the degrees of hearing loss become more severe as you move down the audiogram.
The most severe hearing loss is profound hearing loss, and is shown here at the bottom of the
picture.
The different degrees of hearing loss are defined by pure-tone average, or PTA.
PTA is the average of the individual's pure-tone frequencies at 500, 1000, and 2000 Hertz obtained
with headphones.
Here we explain the first two degrees of hearing loss, mild and mild-to-moderate.
Mild hearing loss includes a pure-tone-average, or PTA of 26-40 decibels.
In quiet situations, speech recognition is fairly unaffected.
However, in the presence of noise, speech recognition may decrease to 50% of words correct.
An individual with mild hearing loss is most likely to miss consonants, especially in high
frequencies.
Mild-to-Moderate includes a PTA of 41-55 decibels.
This individual will understand much of the speech signal in a face-to-face situation
in a quiet environment.
If a hearing aid is not used, the individual may miss up to 50-75% of a spoken message
if the PTA is 40 decibels and 80-100% if the PTA is 50 decibels.
Here we explain moderate, severe, and profound hearing loss.
In moderate hearing loss, the PTA includes 56-70 decibels.
Here, if the patient does not use a hearing aid, they may miss most or all of the message,
even in a face-to-face situation.
This causes great difficulty conversing in group situations.
Someone with severe hearing loss has a PTA of 71-90 decibels.
This individual may not hear voices at all, unless the speech is very loud.
Without some type of amplification, the individual will probably not recognize any speech in
an auditory-only condition.
With amplification, they may recognize some speech and have the ability to detect some
environmental sounds.
Lastly, profound hearing loss affects people with a PTA of 90 decibels or greater.
An individual with profound hearing loss may just perceive sounds as vibrations.
This individual will rely on other senses, mainly vision as a primary sense for speech
recognition.
They probably will not have the ability to detect the presence of even loud sound without
some kind of amplification.
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