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=SRT TE –35 +ABG NTE But no more than: OVERMASK = EM NTE -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. W-22 ListsSo-called PB word lists-- CID W-22 Lists Four lists of 50 words each.

CNC Word Lists Consonant-Nucleus-Consonant words Phonemically balanced NU-6 Word ListsFour 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)

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)/PBmax

Rollover Indices for the preceding examples Normal: ( ) / 100 = 0.0 Rollover: ( ) / 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 BC NTE Use Pink (Speech) Noise, or white noise EM = PBHL TE – IA + ABG NTE

Interpreting Word Recognition Scores Score: General Word Recognition Ability: 90 to 100Within Normal Limits 75 to 90Slight Difficulty 60 to 75Moderate Difficulty 50 to 60Poor < 50Very 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.