Speech Audiometry

SPA 4302

Summer A, 2004

The Diagnostic Audiometer

Equipped with• Inputs for microphones, cassette tapes, or CDs• Volume unit (VU) meters• Circuit for masking noise or mixing noise with

speech in the same ear• Ability to test monaurally or binaurally• Intensity levels ranging from -10 to 110 dB HL• Outputs for auxilliary amplifiers (to speakers)• Talkback system to allow patient/clinician

communication from different rooms/booths

The Patient’s Role in Speech Audiometry

• Pt must know and be able to respond to word in the language of the test.

• Responses:– Verbal repetition– Writing or marking response– Picture pointing– Clicking on choice on computer

The Clinician’s Role in Speech Audiometry

• Must be able to convey to pt their task,

• Keep face from pt’s view

• Understand pt responses

Speech-Threshold Testing

• Speech Detection Threshold: lowest level at which the listener can tell that something is there (when the signal happens to be speech). Also called the speech awareness threshold.

• Speech Recognition Threshold: lowest level at which the listener can actual identify what the speech stimulus is. Also called the Spondee threshold.

SRT Stimuli: Spondees

• 2-syllable words with equal stress

• can 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. (see curve 1 in figure 5.1)

• This provides a much more accurate threshold.

SRT Methods

Descending Approach

• Start approx 10 dB above expected threshold

• Drop in 5 dB steps

• 5 words per level

• Stop when pt misses 5 out of last 6 words

• Threshold = start level – number correct + correction factor

Adaptive Approach

• Like Pure Tone procedure down in 10 dB steps, up in 5 dB steps

• Up to 4 words per level

• Threshold = lowest level at which pt correctly id’s at least 2 words (>50%).

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 setOpen set-client can respond with any word he/she can think of.

• Closed setClosed set-response options are provided for the client (multiple choice test).

• Free responseFree response-client is free to respond or not. • Forced ResponseForced 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 ListsW-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 ListsNU-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)

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.

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)/PBmax0

10

20

30

40

50

60

70

80

90

100

20 40 60 70 80 90

dB HL

% C

orre

ct

NORMAL

ROLLOVER

Rollover Indices for the preceding examples

• Normal: (100 - 100) / 100 = 0.0

• Rollover: (44 - 20) / 44 = 0.54

• 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

• EM = PBHL TE – IA + ABGNTE

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

Predicting WRS from the audiogram: The AI

• The Articulation Index

• Audibility Index

• “Count the dot” audiogram

• If word recognition is poorer than prediction: think neural hearing loss or central disorder.