Transcript 幻灯片 1 - Hearing Aid

Pure Tone Audiometry
Training Course
——Marketing Dept
AD-3A Audiometer
（Frontage）
AD-3A Audiometer
（Side View）
Air-Conduction
Bone-Conduction
Earphone
Earphone
Responsor
Air-Conduction Test
1.Look before you touch
The clinician should assess whether there are any apparent structural
abnormalities and asymmetries of the head in general and the ears in
particular, and perform an otoscopic inspection prior to testing. For
example, is there evidence of active ear disease, eardrum perforations,
atresia, exostoses, external ear abnormalities, or impacted cerumen?
2. Talk before You Test
A case history should be taken at this point. If a case history form was
completed in advance, then this is the time to review it with the patient
for clarification of pertinent details. Always ask if there have been any
changes since the last time he was seen. This is also the time when the
clinician observes the patient to develop a clinical picture of his auditory
status, communicative strategies, and related behaviors.
3. Test Instructions
The patient must know exactly what to do during the test.
The idea of this test is to find out the softest sounds you can hear.
You're going to hear tones from these earphones. There will be many
tones, one at a time. Some of the tones will be loud, but most of them
will be very faint, and many of them will be too soft to hear. Your job is
to press the responser every time you hear a tone, no matter how faint
it is, and not to press the responser whenever you don't hear any tones.
We will test one ear and then the other one. Remember, press the
responser every time you hear a tone, no matter how faint it is.
Do you have any questions?
4. Orientation of the Patient
The patient should be seated in a reasonably comfortable chair.
Audiologists prefer to have the patient seated with her back to the
clinician so that she will not receive inadvertentclues about when test
signals are being presented. Patients and doctors is 90 °angle.
5. Earphone Placement
Red on the right, blue on the left.
The audiologist should check to see whether putting pressure on the
external ear seems to cause the ear canal to close. This is important
because the pressure exerted by the earphones might similarly cause
collapse of the ear canals and give the false impression of a conductive
hearing loss.
Earrings and most eyeglasses (but not contact lenses) must be
removed for both comfort and proper fitting of the earphones. It is also
necessary to remove any other objects (e.g., headbands or other hair
adornments) that could interfere with the placement of the headset (or
the bone vibrator that will be used later). Hearing aids should be
removed, turned off, and put away during the test. Chewing gum and
candy must be disposed of.
Air-Conduction Test
6. Test Frequencies and Testing Order
Air-conduction has traditionally been tested for the octave
frequencies from 250 to 8000 Hz. In this case, pure-tone thresholds
are obtained in the following order for each ear :
1000,2000,4000,8000, retest at 1000,500,250 Hz.
The 1000-Hz retest is done as a reliability check and is expected to
be within ±5 dB of the first 1000 Hz-threshold in that ear, and the
lower (better) of the two is considered the threshold. The semioctaves
(750, 1500, 3000, and 6000 Hz) are tested whenever there is a
difference of ≥20 dB between two adjacent octave frequencies (e.g.,
3000 Hz is tested if the thresholds at 2000 and 4000 Hz differ by 20 dB
or more).
7.Test Method
After a ballpark estimate is obtained, the threshold search procedure is
then begun, which uses the following strategy:
1. Test the better ear first, then the other ear.
2. Air-conduction test first, then the other ear.
3 . Each test tone is presented for 1 to 2 seconds.
4. Used “up-5 down-10” technique typically in pure-tone audiometry.
Conceptual illustration of the “up-5 down-10” technique typically used in puretone audiometry
8. Recording Pure-Tone Thresholds on the Audiogram
NOTE:
False Response
Avoiding Equipment Problems and Tester Errors
Masking
Bone-Conduction Test
Placement variations on the mastoid can result in threshold differences.
For this reason, many audiologists have the patient listen to a readily
audible 500 Hz bone-conduction tone while they shift the vibrator
around on the mastoid. The vibrator is then kept in the location where
the tone sounds loudest. To minimize the chances that the vibrator will
shift once it has been placed, it is wise to instruct the patient to keep her
head still and not to talk during bone-conduction testing.The patient
should also be instructed to tell you if the vibrator moves in any way. It
is also a good idea to provide a strain relief so that an unintentional tug
on the wire will not dislodge the vibrator. This can be done with a small
clip or by looping the wire under the patient's collar.
In this case, pure-tone thresholds
are obtained in the following order
for each ear :
1000Hz,2000Hz,4000Hz, retest at
1000Hz,500Hz,250Hz.
Bone-Conduction Test
Clinical Masking
Why to masking?
It is common to find that the sound being presented to one ear is actually
being heard by the opposite ear. This phenomenon is called cross-hearing
or shadow hearing. To avoid confusion it is customary to call the ear
currently being tested the test ear (TE), and to call the opposite ear, which
is the one not being tested, the nontest ear (NTE). Even the possibility that
the sounds being presented to the TE are really being heard by the NTE
causes the outcome of a test to be suspect.
Hearing level in dB
Frequency
The left ear has profound hearing loss. Without masking right ear, the
sound can be heard by the right ear through the bone-conduction.
When to masking?

BC(T)-BC(N)≥ 10 dB

AC(T)-BC (N)≥40 dB
Masking Steps:
1.Test the two ear's threshold of air-conduction and bone-conduction.
2.Compare the worse ear’s threshold of air-conduction and the better
ear's threshold of bone-conduction, then decide whether and which
frequency to masking.
3. Talk with the patient.
Degrees of hearing loss
Mild hearing loss (25-40dB)
Soft noises are not heard. Understanding speech is difficult in a loud
environment
Moderate hearing loss (41-60dB)
Difficulty understanding speech, especially in the presence of background
noise. Higher volume levels are needed for hearing TV or radio.
Severe hearing loss (61-80dB)
Conversations have to be conducted loudly. Group conversations are
possible only with a lot of effort
Profound hearing loss (>81dB)
Some very loud noises are heard. Without a hearing aid,
communication is no longer possible even with intense effort
Thank you !