Essential Guide to Hearing Loss
2: Understanding Audiograms, Hearing Loss, and Speech
to the Audiogram
How to read an audiogram.
loss and speech intelligibility: the role of vowels and consonants
How hearing loss affects our ability to understand speech. ("I
can hear the words, I just can't understand them.")
Introduction to the Audiogram:
a picture of our hearing thresholds
audiogram is a picture of how well we hear. It shows the softest
sounds we can hear at different pitches or frequencies. This
is known as the threshold hearing level for each frequency.
In the audiogram below, look at the left-hand column. As we
move down the column, the sounds are getting louder and louder.
(See Decibels in Part 1 for
the actual loudness of different decibel levels.)
take a look at the row of figures on the top (250, 500, 1000,
etc.). As we move to the right the sounds are increasing in
pitch, like the keys on a piano. We say they are increasing
in frequency or cycles per second and they are measured in units
called hertz (Hz). Thus, a sound that measures 5000 hertz
is much higher pitched than a sound that measures 250 hertz.
Children can hear sounds up to about 20,000 hertz, but as we
grow older we gradually lose our ability to hear higher-pitched
subject above has a 10 dB threshhold hearing level for most
sounds, meaning he can't hear sounds below 10 dB in volume.
For higher-pitched sounds above 4000 Hz, his threshhold hearing
rises to 20 dB. Any loss up to about 20 dB is considered normal.
(See Ranges of Hearing Loss in
audiogram below is typical of someone with moderate/severe hearing
is the significance of this audiogram? What can it tell us
about this person's ability to understand speech? We'll see
in the next section.
and Speech Intelligibility
the audiogram below, you can see where our basic speech sounds
lie when engaging in normal conversation.
things are important to recognize. For the most part:
are higher pitched than vowels (they lie more to the right
on the chart).
are spoken more softly than vowels (they lie higher on
the chart, in the lower decibel ranges).
factors play a big role in our ability to understand speech.
For one thing, the great majority of people with hearing loss
lose it in the higher frequencies, where the consonants lie.
This is especially true of hearing loss due to aging. So a
lot of older people hear the vowels but not the consonants.
In addition, since consonants are spoken more softly, they
tend to get drowned out in background noise.
note: Remember how we said earlier (Decibels)
that every 10 dB increase or decrease doubles or halves the
perceived loudness of the sound? Keeping that in mind, we
can see that the "a" at 40 dB sounds twice as loud
as the "p" (30 dB) and four times a loud as the
"th" at 20 dB. The "e" (50 dB) sounds
twice as loud as the "a", four times as loud as
the "p", etc.)
vowels and consonants lie in the following regions:
your typical person with hearing loss will have trouble hearing
the consonants in the first place. He may be hanging on by
a thread. Add a little background noise and he may lose them
altogether. And since we're on the subject of speech intelligibility
there is one more fact to consider:
3. Consonants convey
most of the word information; they are much more important
to speech intelligibility than vowels.
is usually possible, for example, to figure out a word if
you remove the vowels. But if you remove the consonants, you're
lost. Try it yourself. Have a friend copy a line of text,
leaving out the vowels. See if you can decipher the words.
Then have him copy another line, this time leaving out the
consonants. You'll find that it's pretty much impossible to
reconstruct the original text.
you or someone you know has ever said, "I can hear
the words, I just can't understand them," this
is probably why.
additional characteristic of consonants: they act as breakpoints,
separating syllables and words from one another. If we can't
hear the consonants clearly, the words seem to run together
and people sound like they are mumbling. And since women and
children have higher-pitched voices than men, it seems like
they mumble more.)
are more important than vowels in understanding speech.
are spoken more softly than vowels, and they tend to get
drowned out in noisy environments.
are higher-pitched than vowels and and most hearing loss
occurs in the higher frequencies.
harder for people with hearing loss to hear the consonants
in the first place, and noisy environments just makes it worse.
No matter how hard they try, they are just not getting it
all. The result is fatigue, frustration, and an increasing
reluctance to engage in socially frustrating situations.
illustrate how a hearing loss affects speech comprehension,
we will now superimpose the audiogram of the person with moderate/severe
hearing loss over the speech zone. The screened area lies
below the subject's threshold of hearing, i.e., what
he can't hear.
you can see, in a normal conversation this person will simply
not be able to hear many of the consonants. The other person
will have to speak considerably louder to be understood. That
is, he will have to push the loudness of his speech above
the subject's threshold of hearing. This obviously puts a
strain on everybody involved.
3: Communication Tips and Strategies