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REVIEW OF THE AUDIOLOGICAL EXAMINATION AND THE AUDIOGRAM
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audiogram
a graphic representation of hearing thresholds as a function of stimulus frequency.
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audiometer
an instrument for measuring hearing sensitivity for a range of frequencies.
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threshold
the level at which sound can be detected only 50% of the time.
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air conduction
refers to when sound travels through the air into the external auditory canal and stimulation progress through the middle ear, inner ear, and to the brain.
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insert earphone
is an earphone whose receiver is attacched to the tube that leads to an expansive cuff. It can be inserted into the external auditory canal.
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bone conduction
refers to the transmission of sound through the bones in the body, particularly the skull. Measured through a vibrator placed on the mastoid.
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air-bone gap
is the difference between air- and bone-conduction thresholds; a difference may indicate a conductive component in the hearing loss.
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sound level
is the intensity of sound expressed in decibels.
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frequency
is the number of regularly repeated events in a given unit of time; ususally measured in cycles per second and expressed in Hertz (Hz).
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Pure-tone Average (PTA)
is often used to assign a label to indicate the degree of hearing loss.
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PTAs: Normal? Mild? Moderate? Moderate to severe? Severe? Profound?
- Normal: 25 dB HL or better in adults or 20 dB HL or better in children
- Mild: 26 - 40 dB HL.
- Moderate: 41 - 55 dB HL.
- Moderate to Severe: 56 - 70 dB HL.
- Severe: 71 - 90 dB HL.
- Profound: poorer than 90 dB HL
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SPEECH AUDIOMETRY
The audiological examination usually includes speech testing in addition to the audiogram. Results will indicate how hearing loss affects a patient's ability to detect and recognize speech and the level of sound necessary for comfortable listening.
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Speech reception threshold (SRT)
is the lowest presentation level for spondee words at which 50% can be identified correctly.
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spondees
are two-syllable words spoken with equal stress on each syllable.
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speech discrimination score
a term that is not used very often anymore, refers to the percentage of monosyllabic words presented and can be identified correctly.
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most comfortable loudness (MCL)
is the level at which sound is most comfortable for a listener.
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uncomfortable loudness level (UCL)
the level at which sound becomes increasingly uncomfortably loud for the listener.
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dynamic range
is the difference in decibels between a person's threshold for just being able to detect speech and the person's threshold for uncomfortable listening.
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loudspeaker azimuth
is the position of the loudspeaker relative to the listener, measured in angular degrees in the horizontal plane.
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loudspeaker
converts electrical energy into sound.
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sound field testing
determines hearing sensitivity or speech recognition ability by presenting signals in a sound field through a loudspeaker.
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Dead air space
are unventilated air spaces.
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PURPOSE OF SPEECH RECOGNITION TESTING
- to determine need for amplification
- to compare performance with listening aid and without it -- to gain patient's confidence.
- to compare different listening devices.
- to demonstrate diminished speech recognition
- to demo the benefits of visual speech info.
- to obtain info about envirnment-related listening issues
- to assess performance longitudinally
- to determine need for auditory or speechreading training
- to determine placement within a training curriculum
- to evaluate the appropriateness of educational placement
- to determine if expected benefit has been achieved
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communication mode
it the means used by the sender to share information with a receiver and may include speech, sign, writing, hand gestures, or any other system of shared symbols.
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phoneme
is the smallest class of speech sounds in a language.
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nonsense syllables
are syllables of speech that have no meaning.
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speech features
are categorical properties of phonemes; a phoneme can be described as a bundle of speech features.
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information transmission analysis
is a statistical procedure that analyzes the transmission of "speech features". If "eepee" and "eetee" are confused then the patient gets credit for the "voicing", but not the "place".
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multidimensional scaling
statistical approach where data points are represented in a geometric space: two phonemes that are similar will be placed near one-another.
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cluster analysis
- A statistical approach that attempts to organize data into groups or clusters: b,d and g would cluster together.
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