Download Hearing Loss

•The nature of sound
•Types of losses
•Possible causes of hearing loss
•Educational implications
•Preparing students for hearing assessment
The nature of sound

A wave phenomenon with two dimensions
1.
Frequency (Hz) - Hertz (cycles per second)
- the number of vibrations of air particles per
second: measured in Hertz
- the human ear has a frequency range of
approximately 20-20,000
- typically hearing is tested from 250-8000 Hz
Hz Low and high frequencies – impact on speech
discrimination:
 Psychological attribute which corresponds to
frequency is pitch
 Low frequency is perceived as low pitch and high
frequency as high pitched sounds
 Middle C on a piano is 250Hz, one octave below is
125 Hz
 High pitched sounds include: a soprano voice, a
doorbell
 In general, vowel sounds are low-pitched and
consonant sounds are high frequency sounds
2. The other dimension is intensity,
measured in decibels (dB)
 “loudness”
 Usable hearing is from 0-120 dB
 dBs are intensity ratios
 20dB is not double of 10dB, but 100 times greater
 The strongest sounds an average person can hear
without pain can be as much as 10 million times
greater in intensity than a sound that is barely
audible
 For example:
- 20 dB a whisper at four feet
- 50 dB - quiet auto ten feet away
-60-70 dB - normal conversation at three feet
- 90 dB - pneumatic drill at ten feet
Speech acoustics
 Spectral characteristics make sound complex
 Vowels are lower frequency - generallly having
their most intense frequency components below
750 Hz
 Consonants are composed of higher frequency
sounds often consisting of a wide range of
frequency components
 In addition, vowels and consonants also differ in
the amount of acoustical energy they produce
 For an equivalent amount of vocal effort, the range
between the loudest vowel (the o sound in the
word dog) and the softest consonant (th sound) is 28 dB
 Vowels are therefore the most intense sounds
heard in speech, while consonants are
considerably less intense
 However, consonants carry the most information
 Consonants above 1000 Hz provide 60% of speech
intelligibility, while vowels below 500 Hz provide
only 5% of speech intelligibility
 <Illustration>
 Thus, shouting at an individual with a
sensorineural hearing loss will do little to improve
comprehension because the vowels will be the
louder and the consonants will continue to be less
audible
 For this reason even mild hearing losses of 30-60
dB can have a big impact on speech intelligibility
Types of loss
 Conductive
 Sensorineural impairments
 Mixed impairments
 Central auditory impairment
Follow up to formal assessment
 Interpreting audiograms - this is the role of the
audiologist
 The job of the educational team is to get as much
information from the audiologist and the speech
therapist about the nature of the speech sounds that
the student can hear - with and without aids
Educational Decisions related to communication strategies
for students with hearing impairments and deafness
Is Sign language the way to
go?
Consider the student’s ability to imitate gestures
Consider the student’s memory
Consider the student’s ability to recognize gestures
Consider the student’s communication needs,
community, and determine whether this is a
match for the student and his/her family
Will you use visual aids?
Consider the student’s visual
discrimination skills
Consider the student’s receptive
understanding of pictures
Consider the student’s family
and community
Will you use a combination of gestures or signs
and visual symbols?
Imitation
memory
discrimination
How far can
the student
go?
Combined
usage – what
for what?
Choosing a communication
system – the issues
 American Sign Language (ASL)
 Oral language
 Cochlear implants
 Combination approaches
Educational Implications
 Literacy: issues in teaching children who are deaf to
read
 Same language community issues
 Teachers trained in working with children/youth with
hearing impairments and deafness
 Social supports and friendship development
Least restrictive environment
 Participation in the core curriculum with support for
language and social engagement
 Interpreters, interveners, and support teachers
 Signing community – same-language community