Thresholds for Speech: - College of Liberal Arts and Sciences
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Transcript Thresholds for Speech: - College of Liberal Arts and Sciences
Speech Audiometry
Thresholds,
Recognition Tests,
MCL &UCL
Testing with Recorded Speech
1000
Hz Calibration tone provided on
recording
Balance calibration tone on VU meter at 0
Live Voice Testing:
Controlled Vocal
Adjust
Effort,
microphone sensitivity
to have the speech balanced at 0 dB on VU
meter
Thresholds for Speech:
Speech
Detection Threshold: lowest level
at which the listener can tell that something
is there (when the signal happens to be
speech).
Speech Recognition Threshold: lowest
level at which the listener can actual
identify what the speech stimulus is.
SRT Stimuli: Spondees
2-syllable
can
words with equal stress
be divided into two monosyllables
e.g.,
hotdog, baseball, whitewash,
mousetrap, birthday, eardrum...
Why spondees?
because
their intelligibility curves rise from
near chance to 100% performance within a
few decibels.
This
provides a much more accurate
threshold.
SRT Methods
ASHA:
Instruct
Familiarize (16 words)
Find Starting Level
Begin Descending
procedure
Thresh = Start Level # C + Corr. Factor
Adaptive
Instruct
Familiarize
Bracket (2-4 wds/level)
Thresh = lowest level
where you get at least
50% correctly repeated.
The SRT should agree with the
PTA
(-8
to +6 dB of best threshold at these
frequencies).
This way we have a double-check on
results.
Exception for steeply-sloped high
frequency losses.
SRT will be better than PTA
In this case use Fletcher average: 500 Hz +
1000 Hz / 2.
Masking for SRT's:
IF
SRT - IA > best BC THRESH in NTE.
WHITE
or PINK NOISE
STARTING LEVEL=SRTTE –35 +ABGNTE
Long Term Spectrum of Speech
And the variance around it.
Bone Conduction SRT's:
useful
in children
useful in malingerers.
Masking for SRT
If
SRT - IA > best BC Thresh NTE
Put in at least:
STARTING LEVEL=SRTTE –35 +ABGNTE
But no more than:
OVERMASK = EMNTE-IA> Best BC Thresh TE
Most Comfortable Loudness Level
Instructions important: you can strongly influence
how a person responds.
"I am going to continue talking to you as I make
my voice louder and softer. I will keep asking you
to tell me whether my voice is too soft, too loud or
comfortably loud."
Do a number of sweeps in level.
normally between 40 and 55 dB above SRT
Uncomfortable Loudness Level
Begin at MCL, raise level as you continue to talk.
"I am now going to ask you to tell me how my
voice sounds to you as I make it louder. Please
tell me if the level is comfortable, a little loud, or
uncomfortably loud.”
Uncomfortable = loud enough so you would not
want to listen to my voice for a long time.
Range of Comfortable Loudness
(Or
the Dynamic Range for Speech)
= UCL – SRT
Normally 100 dB or greater
Unchanged in conductive losses
Can be much smaller in sensorineural
hearing loss
Word Recognition Testing
Open set-client can respond with any word he/she
can think of.
Closed set-response options are provided for the
client (multiple choice test).
Free response-client is free to respond or not.
Forced Response-client must say something.
[Forced choice = closed set forced response.]
Phonetically Balanced Word Lists
selection
of a group of words so that each
phoneme appears with the same frequency
it has in the normal lexicon. Based on
Thorndike-Lorge lists of words and word
frequencies.
So-called
PB word lists-- CID W-22 Lists
Four lists of 50 words each.
CNC Word Lists
Consonant-Nucleus-Consonant words
Phonemically balanced
Four
50-item lists: the NU-6 Word Lists
Alternative Speech Choices
High Frequency Word Lists
• Gardner’s Hi Frequency Word Lists
• California Consonant Test
Nonsense Syllable Lists
• The Nonsense Syllable Test (NST)
Sentence Tests
•
•
•
•
The Synthetic Sentence Identification (SSI) test
Speech Perception in Noise (SPIN) test
Connected Speech Test (CST)
The Hearing In Noise Test (HINT)
Children’s Tests
Word Intelligibility by Picture Identification
(WIPI) test – six pictures to choose from.
Northwestern University Children’s Perception of
Speech (NUCHIPS) test – four pictures to choose
from
Monosyllable-Spondee-Trochee test –
distinguishing word shapes, not identifying
particular words; used in cochlear implant cases.
WIPI Sample Item
NU-CHIPS Sample Item
Administration: once you've
chosen materials
transducer: AC,
BC, or sound field.
level: at some SL (40)--may be specified by
test.
response: repeat, write, or mark on list.
competing noise: what, how loud.
masking: calculate (Test Level - IA) - BC nte
Adaptive Testing
Finding
a threshold, not a % score
Typically in presence of competing noise
Measure has low variance
Not yet common in clinical practice
• (although we will talk about the HINT soon)
Performance-Intensity Functions
PI
function: word recognition scores
obtained at a range of stimulus levels.
Curve reaches a peak (Pbmax), and then
Either remains high (normal), or
Drops at higher levels (Rollover)
Rollover
Index = (PBmax – Pbmin)/PBmax
100
90
80
% Correct
70
60
NORMAL
ROLLOVER
COCHLEAR
50
40
30
20
10
0
20
40
60
70
dB HL
80
90
100
Rollover Indices for the
preceding examples
Normal: (100 - 100) / 100 = 0.0
Rollover: (44 - 20) / 44 = 0.54
Cochlear: (80 - 70)/80 = 0.125
Rollover Indices of 0.45 or greater indicate a neural
(VIIIth nerve) problem.
Cross Hearing & the Need to Mask
If Word level (HL)TE – IA > Best BCNTE
Use Pink (Speech) Noise, or white noise
Suggested Levels:
EM = PBHL TE – IA + ABGNTE + 20 dB
PB Test Level
40 dB HL
60 dB HL
80 dB HL
Masker Level
--40 dB EM
60 dB EM
Reliability of Word Recognition Scores
Range of possible scores upon retest
Thornton & Raffin (1978)
# of Items
Initial
Score
90
100
50
25
10
81-96
76-98
72-100
50-100
50
37-63
32-68
28-76
10-90
20
11-32
8-36
4-44
0-60
NU-6 Words Ordered by Difficulty
Present
10 words- stop if 0 or 1 error
If >1 error, present next 15 words
If < 3 errors (out of 25), stop
If > 3 errors administer all 50 words
Hurley & Sells, 2003
Interpreting Word Recognition Scores
Score:
General Word Recognition Ability:
90 to 100
Within Normal Limits
75 to 90
Slight Difficulty
60 to 75
Moderate Difficulty
50 to 60
Poor
< 50
Very poor
Expected PB max by Hearing Loss
Dubno, J. et al. JSHR 1995
Abnormally Low Word
Recognition for HL
1st % Correct Score
2nd % Score
PTA (dB HL)
SPRINT: Speech Recognition Interpretation Chart
© by Linda M. Thibodeau, 1999
SPRINT: Speech Recognition Interpretation Chart
PTA (dB HL)
2nd % Score
1st % Correct Score
© by Linda M. Thibodeau, 1999
Predicting WRS from the audiogram:
The AI
The Articulation Index
Audibility
Index
“Count the dot” audiogram
If
word recognition is poorer than prediction:
neural hearing loss or central disorder.
Counting Dots: (Mueller & Killion)
Each
dot = 1%
# of dots below HL
line on audiogram
= % correct
identification for
speech.