Intro To Audiometry
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What is the name of the difference in sensitivity between bone conduction and air conduction?
Transmission of sound waves from air through bones to fluid?
Sound waves in the air strike the skull, and transmit vibrations through the bones to the fluid-filled cochlea?
Range of frequencies the normal ear can respond too?
20Hz - 20,000Hz
Most sensitive frequencies the human ear can hear?
Measures equal loudness balance at differenct frequencies?
What is audiometric zero?
Is the point where normal ears can hear at every frequency
Procedure that measures the sensitivity of a person's hearing, relative to the sensitivity of average normal hearing?
The quietest level the patient can hear a tone 50% of the time?
What is an octave?
When the higher frequency is double the lower frequency
Classifications of hearing loss?
- 0-25 Normal
- 25-40 Mild
- 40-60 Moderate
- 60-80 Severe
- >80 Profound
What shape does the audiogram make of a noise induced hearing loss?
Loss of acoustic energy of sound as it travels from the test ear, across the head, to the opposite ear?
What is cross-over?
When you present a sound to the test ear, but the non-test ear hears the sound first.
What is the interaural attenuation for pure tone air conduction testing?
What is the occlusion effect?
The natural increase in loudness of a tone by bone conduction when a blockage is present
What is a change in the threshold of hearing as a result of continuous exposure to sound?
What is the Weber Test?
When you set the bone vibrator in the middle of the patients forehead. Set the frequency to 500Hz and the attenuator to 40dB or louder.
What are the 3 possible results from the Weber Test?
- 1. The patient hears the tone in the ear with the greatest conductive loss at 50 Hz
- 2. If no conductive loss is present, the patient hears the tone in the ear with the best sensorieural loss at 500Hz
- 3. If the loss in both ears is identical at 500Hz, the patient hears the tone in the center of the forehead.
What are the two definitions of Masking?
- 1. Masking occurs when an unwanted sound causes a wanted sound to be inaudible
- 2. Masking is required to keep a better ear busy while testing a poorer ear
What is white noise?
A broad band of noise that contains equal amounts of energy in all frequencies, it is effective for both pure tone and speech testing.
What type of noise consists of a narrow range of frequencies of equal intensity, this noise is not effective for masking speech?
White noise that is filtered to a low and middle frequency spectrum?
What type of audiogram occurs when the contour of the poorer ear follows the contour of the better ear with a 30dB or greater loss?
Shadow Curve or Mirror Audiogram
What is the Interaural attenuation of bone conduction testing?
What is undermasking?
Occurs when the masking noise presented in the better is is not loud enough to eleminate cross-over or Interaural Attenuation
What is overmasking?
Occurs when each 10dB increase in masking shifts the hearing threshold 10dB or more above the plateau.
What is effective masking?
Occurs when the appropriate amount of noise is played in the non-test ear preventing it from taking part in the testing
What is central masking?
A 5dB shift in the threshold of the test ear because of the effects of masking on the Central Nervous System
Rule #1 of Masking?
Air Conduction. Masking is required when there is a 40dB or greater difference in the Air conduction scores between the ears.
Rule #2 of Masking?
Bone Conduction. Masking is required when there is a 15dB or greater difference between the AC and the BC scores of the same ear
Rule #3 of Masking?
Air Conduction. Masking is required when there is a 40dB difference between the AC score of the test ear and the BC score of the non-test ear
Describe a what a typical sensorineural loss audiogram?
- -Thresholds are the same for both AC and BC.
- -Most of the thresholds are not within the normal range
- -There is no conductive component
Describe a Conductive loss audiogram?
- -There is an over-all difference between the AC and the BC
- -The BC thresholds are within the normal limits
Describe a Mixed loss audiogram?
- -There is an over-all difference between the BC and the AC thresholds
- -The BC thresholds are not within the normal range
Describe a Flat Curve Audiogram?
Thresholds are approximately equal at all frequencies
Describe a Gradually Falling Curve audiogram?
Thresholds fall off in the higher frequencies about 5-10dB be octave
Describe a Marked Falling Curve audiogram?
Fall off is between 15-20dB per octave in the higher frequencies
Describe a Rising Curve or Reverse Slope Audiogram?
Loss decreases in the higher frequencies by 5-10dB
Describe the trough shaped curve, or "cookie bite" audiogram?
Less loss at the high and low frequencies then in the middle frequencies
Describe a sudden drop or steep drop audiogram?
Normal or near normal up to 1000-2000 Hz with a steep drop to the next frequencies.
Describe a Fragmentary Audiogram?
There are small islands of hearing at or or two frequencies
What is the point at which spondaic words, spondees, can be repeated 50% of the time?
Speech Reception Threshold
The range of useable hearing between the Speech Reception Threshold (SRT) and the Uncomfortable Level (UL)?
For normal ears this limit is 130dB, anything above it causes discomfort and/or pain?
What are the 5 types of information provided by Speech Audiometry?
- Speech Reception Threshold
- Most Comfortable Level
- Uncomfortable Level
- Dynamic Range
- Speech Discrimination Score
What is the best level for patients to hear and understand speech?
Most Comfortable Level (MCL)
What is the purpose of the Uncomfortable Level in Speech Audiometry?
To determine the upper limit where no further amplification will be permitted in a hearing instrument or accepted by the patient
This uses single syllable word lists, chosen so they approximate a sample of speech sounds occurring in an ordinary conversation?
The Timbre or tonal quality of a complex sound depends on what 3 things?
- The number of frequencies in the complex sound
- the relative strength of each of these frequencies
- the resonance of the chamber surrounding the sound
In a complex tone, this is the lowest frequency (loudest), that predominates?
In a complex tone, this is the weaker, higher frequencies?
Overtones in exact multiples of the fundamental frequency?
Range of frequencies in the spectrum of sound where certain harmonics are relatively loud, these give complex sounds there distinct characteristics?
When does upward masking occur?
Whenever a low frequency sound masks out a higher frequency sound
When does backward masking occur?
When a louder sound occurs immediately after a softer sound, causing the softer sound to be inaudible, even though it occurred first.
When does forward masking occur?
When one sound follows another closely in time and the first sound reduces the sensitivity of recently stimulate cells
This test identifies a measure of dynamic compliance of the tympanic membrane and reflect the algebraic sum of the factors influencing middle ear performance?
What is a Type A Tympanogram?
- It is lower on both ends, with a peak centered around 0. The height of the peak is between 0.3cc-cc
- Normal Middle Ear function
What is a Type Ad Tympanogram?
- Similar to a Type A but, with a deep curve and a tall peak
- Potential causes: ossicular dislocation; loss of elastic fiber in the TM
What is a Type As Typanogram?
- Flattened Type A, shallow curve
- Potential Causes: Otosclerosis; Thickening of the TM
What is a Type B Typanogram?
- No steep peak, little or no variation in impedance over a wide range of pressures
- Potential Causes: Otitis Media; Heavy Debris; Hold in the TM
What is a Type C Tympaogram?
- Looks like a Type A with the peak toward the negative side
- Potential Causes: Eustachian tube is not functioning properly
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