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Identify the hearing process
Contents
1
Key to resources
1
Introduction
2
The anatomy and physiology of the ear
2
Psychoacoustics
4
Sound and speech
8
Tinnitus
10
Hyperacusis
11
Summary
12
Further reading
12
Feedback to activities
12
This learning guide is based on the following resources:
*Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Pearson, Boston
Audiometry–Anatomy of the Ear–3064-1/HLSP
Audiometry–Psychoacoustics–3064-3/HLSP
*Note: The pages number references provided for Introduction to Audiology
in this task guide are based on the 9th edition. If you have an earlier or later
edition of the textbook, these pages numbers may not be the same (but may
be approximate). The headings are likely to be the same or similar in the
various editions.
Key to resources
Resource
number
Resource title
1
Audiometry–Anatomy of the Ear–3064-1/HLSP, pages 7–15
2
Introduction to Audiology, pages 223–229, 240–247, 278–289 and 316–319
3
Audiometry–Psychoacoustics–3064-3/HLSP, pages 5–29
4
Introduction to Audiology, pages 25–50
Identify the hearing process
© NSW DET 2007
1
Introduction
To be able to assess the hearing of children, you must have an understanding
of the processes involved with hearing. This involves having some
understanding of the anatomy of the ear and its physiology as well as the
properties of sound and the acoustic content of speech.
In following this guide you will learn about the process of hearing.
Specifically, you will learn about:

anatomy of the hearing mechanism

psychoacoustics

sound and speech

tinnitus

hyperacusis.
This is a complex and diverse area of study. The aim of this task guide is to
provide you with background information. This task guide should form a
basis for further study. There are many excellent texts and journals that you
can use for further study. The internet provides a rich source of information
but be careful to check the source from which that information comes.
The anatomy and physiology of the ear
You may have already done a fair amount of learning about the anatomy
and physiology of the ear. If you have already read the material and feel that
you are able to attempt Activity 1, please go ahead. You may, however,
prefer to review the material first—in which case, go to resources 1and 2
(see below).
Go to Resource 1
Go to Audiometry–Anatomy of the Ear–3064-1/HLSP and read pages 7–15.
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© NSW DET 2007
Go to Resource 2
Go to Introduction to Audiology (Martin and Clark), pages 223–229, 240–
247, 278–289 and 316–319. Read through the information on ‘Anatomy and
physiology of the outer ear’, ‘Anatomy and physiology of the middle ear’,
‘Anatomy and physiology of the inner ear’ and ‘Anatomy and physiology of
the auditory nerve and ascending auditory pathways’.
There are literally hundred of websites with information about the anatomy
of the ear. Here are some you might like to consult:
‘Promenade ‘round the cochlea’ (France): http://www.cochlea.org/
‘Auditory and vestibular pathways’, The Washington University School of
Medicine: http://thalamus.wustl.edu/course/audvest.html
‘Cochlea and auditory pathways’, College of Veterinary Medicine,
University of Minnesota:
http://vanat.cvm.umn.edu/NeuroLectPDFs/LectAuditorySys.pdf
‘Auditory anatomy’, Brain Connection (USA):
http://www.brainconnection.com/topics/?main=anat/auditory-anat2
Some Youtube sites you might want to look at are:
http://www.youtube.com/watch?v=cfAyPbFYGJw
http://www.youtube.com/watch?v=7a2aoZeZhZ8&feature=related
http://www.youtube.com/watch?v=8wgfowbbTz0&feature=related
http://www.youtube.com/watch?v=ei_vRzp8IN0&feature=related
http://www.youtube.com/watch?v=WO84KJyH5k8&feature=related
Identify the hearing process
© NSW DET 2007
3
Activity 1
Draw a diagram of the peripheral hearing mechanism. Describe its structure and function.
Draw a diagram of the central auditory pathways.
For feedback on this activity, go to the end of this task guide.
Psychoacoustics
You may have already done a fair amount of learning in the area of
psychoacoustics. If you have already read the material and feel that you are
able to attempt Activity 2, please go ahead. You may, however, prefer to
review the material first—resources 3 and 4 as well as the websites listed
will help you with your review (see below).
Go to Resource 3
Go to Audiometry–Psychoacoustics–3064-3/HLSP and read pages 5–29.
Go to Resource 4
Go to Introduction to Audiology, pages 25–50 and read through the
information about sound and its measurement.
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© NSW DET 2007
Here are some websites that you may find useful:
‘Sound and learning’, Georgia State University, Atlanta, Georgia:
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soucon.html
‘The physics of sound’, University of California, Davis:
http://interface.cipic.ucdavis.edu/CIL_tutorial/3D_phys/3D_phys.htm
National Science Foundation (Virginia, USA):
http://www.nsf.gov/news/classroom/physics.jsp – click on the Physics
classroom website for resources on sound.
Activity 2
Answer the questions below.
1
What must exist before sound can be generated?
_____________________________________________________________________
_____________________________________________________________________
2
Describe how sound waves are produced.
_____________________________________________________________________
_____________________________________________________________________
3
What affects the speed of sound?
_____________________________________________________________________
_____________________________________________________________________
4
Define the terms: diffuse field; free field; transmission; diffraction; reverberation;
reflection; refraction; absorption.
_____________________________________________________________________
_____________________________________________________________________
Identify the hearing process
© NSW DET 2007
5
5
Why is the decibel used to describe sound?
_____________________________________________________________________
_____________________________________________________________________
6
What is dBHTL?
_____________________________________________________________________
_____________________________________________________________________
7
What does 0dB mean?
_____________________________________________________________________
_____________________________________________________________________
8
How does dBSPL relate to dBHL?
_____________________________________________________________________
_____________________________________________________________________
9
What is dBSL?
_____________________________________________________________________
_____________________________________________________________________
10 Why is one sound louder than another?
_____________________________________________________________________
_____________________________________________________________________
11 What is the level of normal conversational speech?
_____________________________________________________________________
_____________________________________________________________________
12 At what level are sounds painfully loud?
_____________________________________________________________________
_____________________________________________________________________
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13 How would you define ‘intensity’?
_____________________________________________________________________
_____________________________________________________________________
14 What are standing waves?
_____________________________________________________________________
_____________________________________________________________________
15 What is the inverse square law?
_____________________________________________________________________
_____________________________________________________________________
16 What do we mean by ‘sound frequency’?
_____________________________________________________________________
_____________________________________________________________________
17 What is the frequency range of human hearing? At what frequencies is the ear most
sensitive?
_____________________________________________________________________
_____________________________________________________________________
18 What is the principle behind the Fourier analysis?
_____________________________________________________________________
_____________________________________________________________________
19 What is resonant frequency?
_____________________________________________________________________
_____________________________________________________________________
20 What is binaural advantage?
_____________________________________________________________________
_____________________________________________________________________
Go to the end of this task guide for feedback on this activity.
Identify the hearing process
© NSW DET 2007
7
Sound and speech
You may have already done a fair amount of learning in this area. If you
have already read the material and feel that you are able to attempt
Activity 3, please go ahead. You may, however, prefer to review the
material first.
Go to Resource 3
To review the material on sound and speech, go to Audiometry–
Psychoacoustics–3064-3/HLSP and read pages 31–36.
The most important thing we do with our hearing is communicate with
others. For most of us, our ears are what we use to learn to speak and our
ears are what we use to understand what other people are trying to say to us.
Of course, there are many ways to communicate including signing and other
visual forms of communication. This section is about spoken
communication.
This website describes some terms used in linguistics:
http://www.geocities.com/CollegePark/3920/.
Activity 3
Answer the questions below.
1
What is the range of frequencies produced by humans?
_____________________________________________________________________
_____________________________________________________________________
2
Which frequencies are most important for understanding speech?
_____________________________________________________________________
_____________________________________________________________________
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Identify the hearing process
© NSW DET 2007
3
How can you tell if a sound is voiced or voiceless?
_____________________________________________________________________
_____________________________________________________________________
4
Are vowels voiced or voiceless sounds?
_____________________________________________________________________
_____________________________________________________________________
5
What is redundancy in language?
_____________________________________________________________________
_____________________________________________________________________
6
Why is hearing described as our distance sense?
_____________________________________________________________________
_____________________________________________________________________
7
At what frequencies is the ear most sensitive?
_____________________________________________________________________
_____________________________________________________________________
8
What are the suprasegmental features of speech?
_____________________________________________________________________
_____________________________________________________________________
9
What role does context play in the communication process?
_____________________________________________________________________
_____________________________________________________________________
10 What are visual cues?
_____________________________________________________________________
_____________________________________________________________________
Go to the end of this task guide for feedback.
Identify the hearing process
© NSW DET 2007
9
Tinnitus
Go to Resource 2
Go to Introduction to Audiology, pages 429–432 to read ‘Management of
tinnitus’.
Children do experience tinnitus but it is rare for clinicians or doctors to ask
children. Children do not usually mention tinnitus unless specifically asked.
‘Tinnitus’ is the term used to refer to the ringing sound many people
experience. People describe their tinnitus as being many different sounds,
eg, cicadas, buzzing and beeping. It can be constant or intermittent, in one
ear or both and it can range from mild to severe.
When we use the word ‘tinnitus’, we are usually referring to subjective
tinnitus. Subjective tinnitus is only heard by the person experiencing it and
can only be described by them.
The other kind of tinnitus is objective tinnitus. If a person is experiencing
objective tinnitus, it can be heard by someone else. This type of tinnitus is
often an indication of a serious medical condition and the person must see
their medical practitioner immediately.
Tinnitus can occur with many conditions of the ear, eg, it can occur
temporarily with occluding wax or a middle ear condition. It is sometimes
an indication that damage has occurred, eg, after going out to a noisy
concert you might experience tinnitus with hearing loss for a day or two
afterwards.
Tinnitus can cause some people a great deal of distress. These people can be
helped by a number of treatment or management options. However, they
must first see and ENT specialist (ear, nose and throat specialist) to exclude
any reasons for the tinnitus that may require medical treatment.
People that have unilateral tinnitus or tinnitus that starts very suddenly
particularly with other symptoms like hearing loss and vertigo (dizziness)
should be asked to see their family doctor and obtain a referral for an ENT
specialist.
There is a lot to learn about tinnitus and it is a fascinating area. If you are
interested in learning more, there are many books and websites that you can
refer to. The information produced by self-help groups provides a great
starting point.
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© NSW DET 2007
Now visit these websites:
Australian Tinnitus Association (NSW): www.tinnitus.asn.au
Victorian Deaf Society (Vicdeaf): www.vicdeaf.com.au/tinnitusmanagement
The Tinnitus and Hyperacusus Site (UK): www.tinnitus.org
TinnitusTreatment (Texas, USA): http://www.tinnitustreatment.com/
Western Hearing Services and Tinnitus Management (Australia):
www.tinnitus.com.au
National Institute on Deafness and Other Communication Disorders (USA):
www.nidcd.nih.gov/health/hearing/noiseinear.asp
Grossman M (9/7/2001) ‘Tinnitus Management Alternatives’, Audiology
Online (USA):
http://www.audiologyonline.com/articles/article_detail.asp?article_id=294
Hyperacusis
Go to Resource 2
Go to the Introduction to Audiology, page 432 and read through the
information on hyperacusis.
It is not unusual for a child to react in a negative way to sudden loud noises.
This is particularly true when a child has middle ear effusion. It is not clear
why this happens but it is best to respond to a child in a non-emotional way
and say something like ‘That was a loud noise!’ and then perhaps to tell
them what the noise was.
Hyperacusis is an extreme sensitivity to everyday sounds and children do
experience it. If this is an issue for a child that you are assessing, be careful
not to start at very high levels when doing the hearing test. Also, you may
not be able to do acoustic reflex testing.
Hyperacusis is distressing to the people who experience it. People with
hyperacusis often feel that they have exceptionally good hearing but this is
not true. They are very sensitive to sound and are unable to tolerate
everyday sounds and may resort to wearing ear plugs to be able to cope with
their daily lives.
Identify the hearing process
© NSW DET 2007
11
The treatment and management options that have been developed for
tinnitus have been found to work well for people with hyperacusis.
Wearing ear plugs may be useful in the short term. The major treatment
programmes for hyperacusis include desensitisation and avoid the use of ear
plugs.
Find out the clinics in your region that can help people with hyperacusis so
that you can provide your clients with this information. People with
hyperacusis often feel that they are alone and cannot be helped but this is
not true.
Now visit these websites:
‘Tinnitus Management’, Victorian Deaf Society:
www.vicdeaf.com.au/tinnitus-management
Jastreboff MM and Jastreboff PJ (18.6.2001) ‘Hyperacusis’:
www.audiologyonline.com/articles/article_detail.asp?article_id=291
Summary
In this topic you have learnt about hearing processes. This learning guide
has given you some background information in this area.
Further reading
If you wish to carry out further research, there are many texts and websites
that you can investigate. The websites mentioned within this task guide will
help you.
Feedback to activities
Activity 1 feedback
1
Draw a diagram of the peripheral hearing mechanism. Describe its
structure and function.
See page 10 of Audiometry–Anatomy of the Ear–3064-1/HLSP to
compare your diagram.
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© NSW DET 2007
The peripheral hearing mechanism is composed of the outer, middle
and inner ears. Outer ear – the pinna collects the sound, which travels
down the external auditory meatus to the eardrum. The ear canal has a
protective function with cerumen and hairs to keep the ear canal clean
and at a constant temperature. The ear canal also works as a tube
resonator. Middle ear – has the ossicles and the Eustachian tube, is airfilled and acts as an impedance-matching transformer. The ossicle rock
and the sound reaches the oval window. Inner ear – cochlea and
semicircular canals, the sensory organ of hearing and the balance
mechanism. The sound is analysed by the cochlea with the Organ of
Corti responding to the sound tonotopically, transmitted from the outer
hair cells to the inner hair cells to the eighth nerve.
2
When drawing your diagram, note that the central auditory pathway
consists of:
CN
cochlear nucleus
SOC
superior olivary complex
LL
lateral lemniscus
IC
inferior colliculus
MG
medial geniculate
See page 316 of Introduction to Audiology to compare your diagram
with the one presented.
Activity 2 feedback
1
What must exist before sound can be generated?
A sound source that vibrates and a medium for the sound to travel
through.
2
Describe how sound waves are produced.
A vibrating sound source moves the molecules of the medium, usually
air. The molecules are pushed into the ones nearby and then are pushed
back; they rebound and overshoot their original position and then return
to their resting place. Each individual molecule does not move far from
its original position. Sound waves are a series of compressions and
rarefactions that cause a change in pressure.
3
What affects the speed of sound?
Temperature, humidity and the density of the medium.
4
Definitions:
Diffuse field: there are barriers and interference affecting the sound.
Free field: no barriers or interference affecting the sound.
Identify the hearing process
© NSW DET 2007
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Transmission: sound goes through a barrier.
Diffraction: sound waves are scattered.
Reverberation: sound waves are bounced off a barrier even after the
sound source has stopped.
Reflection: sound waves are bounced off a barrier.
Refraction: sound waves bend when they meet a barrier.
Absorption: sound gets caught in a barrier.
5
Why is the decibel used to describe sound?
It is an easy way to use large numbers and it is like the way that the ear
responds to sound.
6
What is dBHTL?
Decibels hearing threshold level, based on correction figures from
healthy young adults.
7
What does 0dB mean?
The reference point; it does not mean no sound. The letters after it
describe what the reference point is. For example, dBSPL means that
0dBSPL is 20micropascals.
8
How does dBSPL relate to dBHL?
dBHTL is based on the level of sound in dBSPL that is required to just
hear a particular frequency for a group of otologically normal young
adults. This level is then used to calibrate an audiometer so that
0dBHTL can be used as a comparison for an individual’s hearing to the
normal range.
9
What is dBSL?
Decibels sensation level.
10 Why is one sound louder than another?
It has greater amplitude, ie, the molecules have moved further from
their resting place.
11 What is the level of normal conversational speech?
65dBSPL
12 At what level are sounds painfully loud?
At around 120-140dBSPL, regardless of hearing levels.
13 How would you define intensity?
The decibel defines intensity.
14 What are standing waves?
These are also called dead spots, where two sounds cancel each other
out because they are exactly the same sound but out of phase (1800
degrees out of phase).
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Identify the hearing process
© NSW DET 2007
15 What is the inverse square law?
It tells us that as a sound moves away from its sound source it gets
softer. In a free field, the sound is decreased in inverse proportion to the
square of the distance from the source.
16 What is meant by ‘sound frequency’?
Frequency is related to how often the molecules return to their resting
place. It is cycles per second.
17 What is the frequency range of human hearing?
20 to 20000 Hz
18 What is the principle behind Fourier analysis?
That all complex sounds can be broken down into their component pure
tones.
19 What is resonant frequency?
The frequency at which an object vibrates most easily and for longest.
20 What is binaural advantage?
It is the advantage of having two ears working together. The hearing
has to be about the same in both ears. Includes binaural summation
(hearing better by about 3dB), being able to localize sounds and hearing
better in background noise (binaural squelch effect).
Activity 3
1
What is the range of frequencies produced by humans?
85Hz to 11000Hz
2
Which frequencies are most important for understanding speech?
500Hz to 4000Hz
3
How can you tell if a sound is voiced or voiceless?
If you put your hand on your throat you can feel it vibrating as you say
the sound.
4
Are vowels voiced or voiceless sounds?
In English, vowels are all voiced.
5
What is redundancy in language?
This is the extra information in language that means that we can
understand even when some of the elements are missing. It allows a
message to be predictable in many instances.
6
Why is hearing described as our distance sense?
It keeps us in contact with our surroundings and we can often hear
things that we can’t see or touch. So we do not have to be in the
immediate vicinity of something that is producing a sound.
Identify the hearing process
© NSW DET 2007
15
7
At what frequencies is the ear most sensitive?
The ear is most sensitive in the range 500Hz to 4000Hz. These
frequencies are also the most important for speech understanding.
8
What are the suprasegmental features of speech?
These include stress and intonation. For example, they help us know is
an utterance is a statement or a question.
9
What role does context play in the communication process?
Context allows us to be able to understand what is said without
necessarily hearing every sound. It forms part of the redundancy of
language. If we know the topic of conversation, we are able to follow
the message more easily.
10 What are visual cues?
These include lip-reading and speech-reading. They help us to
understand what is said especially when the signal is badly degraded.
They are particularly useful to differentiate consonants that sound
similar but are produced in different locations, eg, b/d/g.
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Identify the hearing process
© NSW DET 2007