1 - Audiometry Flashcards
Types of Audiometers
Diagnostic (Clinical) vs. Portable
Speech vs. Pure Tone
Manual vs. Automatic
Audiometer
An electrical devise
Presents CONTROLLED acoustic signals
Tests some aspect of auditory function
Clinical Audiometer
Desktop design
Allows clinicians to perform most audiometric tests
Consists of two channels so each ear can be tested seperately
Portable Audiometer
Allows testing in almost any quiet environment
Depending on the model, it can perform only simple tests to a thorough audiological exam
Where might portable audiometers be used?
Schools
Industrial Settings
Homes
Etc.
Manual Audiometer
Examiner controls the presentation of the signal
The most common form of both portable & clinical audiometers
Automatic Audiometer
Usually computerized
Programmed to present signals based on a specific response from the person (usually by pressing a button)
Commonly used in mobile testing vans that are set up to test multiple people at once
Parts of Audiometers
5
Oscillator
Intensity Dial
Presentation Switch
Output transducers
Input signal selector
What does the oscillator do on an audiometer? How does it work? Where is it?
(4)
Selects the frequency of a pure tone
Available at octave and mid-octave points between 125-8000 Hz.
Some can extend even higher
It is an internal component but there will be a dial or a switch on the panel
What does the presentation switch do on an audiometer? How does it work?
Allows the examiner to present the signal to the patient
The length of time that the button is held down determines the length of the signal.
It is also called an “interrupter switch” because the tone can be set to play indefinitely until switch is re-pressed
What does the intensity dial do on an audiometer? How does it work?
Controls the intensity
Usually ranges from -10 to 120 dB HL
The intensity can usually be modified in 5 dB steps
Why can the highest and lowest frequencies on an audiometer not be played at the highest intensity setting?
It takes a large amount of energy to produce these tones
They come out distorted
What does the output transducer do on an audiometer?
Coverts energy into a sound signal
What are some types of output transducers?
Supra-Aural Earphones
Insert Earphones
Bone Oscillators
Speaker
What are supra-aural earphones?
Standard headphones
Goes on top of pinna and ear canal
What are insert earphones?
A long piece of tubing that is inserted into the ear canal via a soft, disposable tip
What is a downside to supra-aural headphones?
They can collapse the ear canal due to pressure. Insert headphones can prevent this
What are bone oscillators?
A small vibrator connected to a headband
It is usually placed on the mastoid bone behind the ear, but is sometimes used on the forehead
This sends a sound signal straight to the inner ear
When are speakers normally used?
When testing infants or small children who are unwilling to use headphones
Can also be used to test the efficacy of hearing aids.
What does the input signal selector do on an audiometer?
A set of switches use to choose whether the signal will be a pure tone, a speech signal, a noise, or a signal from an outside source.
On the clinical audiometer, this is often a separate set of controls but is incorporated into the frequency selector switch on portable units
This can also modulate pure tones creating a warbling sound
Why is a warbling tone used?
It can help patients with short attention spans or with tinnitus
Why must audiometers be calibrated?
4
To ensure the machine…
....produces tones at a specified level ....produces tones at a specified frequency ....presents the tone only to the correct earphone ....presents a tone free of distortion or unwanted noise interference
Who regulates audiometer measurements?
ANSI
American National Standards Institute
How often must audiometers be calibrated?
Once a year but should also be checked by the examiner prior to use
When an examiner checks an audiometer prior to its use, what are they looking for?
An undistorted signal (Are cords undamaged?)
That the frequencies and intensities are accurate (can be done by performing a selftest of hearing)
Most audiometric testing occurs at low levels to ____________.
Determine the threshold of hearing
What do most audiology clinics use to perform testing?
A sound-treated test booth
This is not sound proof!
What is the first step to an audiometric test?
To position the patient properly
- No distractions - Unable to see examiner - Where examiner can see patient
What instructions are given to the patient prior to the testing?
(7)
The purpose of the test is find the faintest sound you can hear
Sit quietly without talking
Respond whenever you think you hear the tone, even if it’s quiet
It’s important to respond quickly when you hear the tone and/or when the tone stops
Each ear will be tested separately with tones of different pitches
Drinking, eating, chewing, smoking, etc. will interfere with the test
Any questions?
When placing earphones, be sure to _________________ and that ____________.
Remove hats, headbands, glasses, etc.
Earphones are directly over the ears
Which ear is normally tested first?
The better ear
If unknown, then the right
How is the initial test performed?
Starts at 1000 Hz.
Then performs the higher frequencies: 2000, 4000, & 8000 Hz
Retesting of 1000 Hz
Then the lower frequencies: 500, & 250 Hz.
125 Hz is usually only reserved for those with severe to profound hearing loss
If there is a 20 dB difference between octaves, then ___________.
The mid-octaves should be tested to determine the slope with greater accuracy
What other reasons are there to test the mid-octave frequencies?
Monitoring the effects of noise exposure
Improving the precision of technologically advanced hearing aids
What happens after the patient has been given instruction, fitted with headphones, and given the first tone?
There should be a preparatory phase (familiarization) to insure that the patient understands what to do
This is done by dropping the test tone in 10 dB increments
What is the “Down 10, Up 5” rule?
If the patient responds to a tone, the examiner will drop it 10 dB until there is no response
If the patient does no respond to a tone, then the examiner will raise the tone 5 dB until there is a response
Why is the mastoid bone usually used for testing bone conduction?
It is close to the inner ear
What are some hurdles to using the mastoid bone for testing bone conduction?
The shape of the bone and its ability to move creates inconsistency in device placement
What is sensorineural sensitivity?
The sensitivity of the inner ear and auditory pathways
Can you test each ear separately using bone conduction?
No. There is no way to separate one ear from the other
What is the point of audiometry?
To answer the following questions:
Does the person hear at a normal level?
How well does the person understand speech presented a comfortable listening level?
Audiometry can test hearing, but it can also help in _________.
Diagnosing medical problems or pathologies
What are some pathologies of the ear that do not create hearing loss?
Vertigo
Tinnitus
What is the purpose of tone audiometry?
To measure the hearing sensitivity in the range of frequencies most important in understanding human speech
What frequency range is usually measured in an audiogram?
250-8000 Hz
What frequency range is most important in understanding speech?
200 - 6000 Hz
What does signal detection not tell us?
What the person actually heard
Was it a pure tone, distorted, a tapping sound, etc.
What is the difference between screening and threshold audiometry?
Screening audiometry is designed to evaluate a large number of people in a short amount of time
Threshold audiometry looks at hearing sensitivity across the range of frequencies important for everyday communication
What is the pathway for air conduction?
Outer Ear
Middle Ear
Inner Ear
Eight Cranial Nerve
Brainstem
Cortex
What is the pathway for bone conduction?
Inner Ear
Eight Cranial Nerve
Brainstem
Cortex
What are important considerations for threshold measures according to ASHA?
(5)
Tone Duration
Interval Between Tones
Level of First Tone Presented
Levels of Succeeding Tones
Definition of Threshold
Why is the familiarization process at the beginning of a hearing test important?
It assures the patient knows what to do
Are the procedures for performing a pure tone test different when using air conduction versus bone conduction?
No
Which ear do you begin with?
The better ear
If unknown, it’s usually the right
How long are tones presented?
1-2 seconds
Why is it important to vary the time interval between signals?
Unpredictability leads to better accuracy
The level of the first presentation of tone for threshold measurement should be ________ the level of the listeners response to the familiarization presentation
10 dB below
How is threshold defined during a audiometric test?
It is the lowest level that is responded to with a minimum of three responses at the same level
When should inter-octaves be tested?
When the thresholds between two octave differ by 20 dB or more
What might create false positives?
The tester is using detectable intervals between signals
The patient may not understand what to do
When are false negatives usually seen?
When there is an outside motivating factor like insurance money or military service
What does a higher number on an audiometer mean?
There are more funcions
What does ANSI stand for?
American National Standards Institute
What does ANSI do?
Sets standards for many instruments and measures
Are ANSI standards stagnate?
No, they are in a constant state of revision
New standards are issued or reaffirmed every 5 years
Pure Tone Air Conduction can be performed using _____, _____, or _____.
Supra-Aural Earphones
Insert Earphones
Sound Field
What are the benefits to insert earphones?
Prevent ear canal collapse
Increase interaural attenuation
Provide better attenuation of ambient noise
Are lighter and more comfortable
Why test by bone conduction?
Helps determine…
...Site(s) of lesion ...Severity of loss ...Management
What might happen if bone conduction tests were omitted?
Misdiagnosis and mistreatment of the problem
What is the interaural attenuation for bone conduction? What does this mean?
0 dB
When performing a test by bone conduction, there is no way to tell what cochlea received the information (Right? Left? Both?)
What is the Weber Test?
A bone conduction test of lateralization
You place vibrating tuning fork on the patient’s head and ask where they hear the tone
What is the Air Bone Gap?
When Air Conduction Thresholds are significantly WORSE than Bone Conduction Thresholds
The air-bone gap must be ______ than _____ to be deemed clinical significant
Greater
10 dB
When do we see air bone gaps?
With mixed and conductive hearing loss
Can Bone Conduction ever be worse than Air Conduction
No
What is Ossicular Discontinuity?
When the ossicles do not connect
When performing a bone conduction test, where can the bone oscillator be placed?
On the mastoid bone or on the forehead
What are the advantages of using the forehead for bone conduction tests?
Less curvature of the skull at forehead
Tissue and bone are more consistant
What are the disadvantages of using the forehead for bone conduction tests?
Harder to keep vibrator in place
More force is required to elicit a response (10-15 dB more intensity)
What are the ASHA procedures for bone conduction tests?
4
The test ear is uncovered
The threshold search is the same as for air conduction
Frequencies are limited to 250 - 4000 Hz
When testing at lower frequencies (250 & 500 Hz), ambient noise must be low
Whats the difference between Hearing Sensitivity versus Sensorineural Senstvity?
Hearing Sensitivity refers to someones ability to hear with their entire auditory system, a.k.a., “normal hearing”
Sensorineural Sensitivity refers to someones ability to process sound using just the cochlea and the neural system
What is the interaction between SPL and HL?
0 dB HL at any given frequency corresponds physically to the appropriate zero reference SPL for that frequency (the SPL threshold measurement)
0 dB HL has a different SPL reference depending on the frequency being measured
