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Flashcards in Speech Threshold Assessment Deck (20):
1

Describe the speech stimulus. What can we define/not define? How does a complex signal vary? What is the speech spectrum composed of? Where is the peak? Where is the rolloff and by how much? Which speech spectrums are similar? How does the intensity of speech components vary?

The Speech Stimulus - We can define a pure tone, but we can't define a speech signal

• A complex signal changes from moment to moment: varies in amplitude, duration, and frequency components

• the speech spectrum: speech is composed of many frequencies

  • Peak: 500-700 Hz
  • Rolloff above 1k: 10-12 dB/octave
  • Similar spectrum for males, females, different languages

• Relative intensity of speech components

  • Strongest components: vowels  
  • Weakest components: consonants      
  • Can differ by 30-35 dB

2

Describe the thresholds for speech. What is detectability, intelligibility and absolute intelligibility? What does detectability agree with? What is the relationship between the thresholds?

• Detectability: faintest level at which an individual can detect speech 50% of the time (SDT)

  • Raise your hand if you can hear the speech - will agree with the best threshold on the audiogram

• Intelligibility: lowest intensity where individual correctly repeats the material 50% of the time (SRT)

• absolute intelligibility: faintest level at which individual repeats 100% of the material

 

relationship between thresholds

• SDT is 8-9 dB< SRT, which is 4-5 dB< θ of abs. intellig.

• SDT ≈ best θ on audiogram (.25 – 4k Hz)

• SRT ≈ average hearing in speech frequencies (.5- 2k Hz)
 

3

What are the uses of speech thresholds?

• validate pure tone audiogram

  • Evaluate relationship between sensitivity for speech and pure tones

• use as a reference intensity level

  • Supraθ speech recognition (x dB SL re: SRT)

• used to estimate hearing sensitivity

  • For difficult to test patients

• used to determine hearing aid candidacy, estimate benefits, monitor performance
 

4

Describe the history of speech testing. What tests came first? What was invented in 1877 and what did it allow for? Describe the first speech audiometer. 

  • Whispered speech tests
  • Invention of phonograph (1877) – Edison
    • Could present recorded material
  • First speech audiometer (1926) – Bell Labs
    • Presented phonographic recordings (digit pairs)
    • Reduced intensity in 3-dB steps
    • Measured articulation function for speech:  
      • % correct vs. presentation level
    • SRT corresponds to 50% point
    • Developed Bell Tel. Intelligibility Lists (49 lists; 50 sent)

5

Describe the history of speech thresholds. Monitored live voice testing and Harvard psychoacoustics labs. What did PAL develop? What were the criteria for selection? How was SRT measured?

  • Monitored live voice testing (1942)
    • Hughson & Thompson
    • Hooked VU-meter to speech audiometer to monitor intensity of voice
    • Measured SRT via pure-tone audiometric technique
    • Noted a linear relationship between pure tone & speech θ
  • Harvard Psychoacoustics Labs (PAL) (Hudgins, et al., 1947)
    • developed materials for measuring SRT
    • Criteria for selection:
      • Highly audible and equally audible
      • Familiar vocabulary
      • Phonetic dissimilarity
      • 84 words chosen = all spondees (= stress on 2 syllables)
    • Recordings of spondee word lists
    • developed tabular form for measuring SRT
      • Not necessary to plot entire artic f’n
      • Assign a particular amount of attenuation to each test word - certain number of words at a level 
      • Calculate SRT

6

Describe the history of speech thresholds. CID. What were their stimuli? What was at the beginning of each list? What method did they use? How big were their steps? How was threshold determined? What was the correction factor? What did they try to produce? What is now on a CD?

  • CID (1950’s) – Hirsh – spondee disc recordings because though PAL words were unfamiliar 
    • Stimuli: more familiar words than PAL
    • Recordings: W1 – constant level, W2 – stair-step - built in amount of attentuation
      • Cal tone at beginning of list: equivalent in intensity to level of the test words  
    • tabular method:  start at supraθ level
      • 3 words/step, in 3dB steps
      • Assign 1 dB for each correct word; count # words correct
      • Subtract # correct from starting level, add correction factor
  • Efforts to produce “homogeneous” list of spondees
    • Θ for different spondees obtained at similar levels
    • Lists available with 15 selected spondees 
  • CID W1 now on CD (Chambron et al., 1991) – female talker; derive same Θs as Hirsh recording

7

Describe the Tillman-Olsen (1959) method ASHA (1988) method for SRT's. What kind of method is it? What is the preliminary phase? What is the test phase? How is SRT calculated? Why is the correction factor 1?

  • A descending method with 2 phases
  • Preliminary phase
    • Read words to S at supraθ level, w/o visual cues
    • Discard any words the S can’t repeat
    • Give S instructions
      • You're going to hear a series of words, repeat even when they get soft
    • Present words formally at supraθ level
      • Present 1 word, if correct, descend by 10 dB
        • If got word wrong, present another word
      • Continue until S misses 2 words at 1 level
      • Increase level by 10 dB -> starting level
  • Test phase – record responses right or wrong
    • Present 2 words/level
    • S must repeat 1st 5/6 words correctly
    • Descend in 2-dB steps
    • Continue until S misses last 5/6 words
  • calculation of threshold
    • Starting level - # correct + 1 dB

8

What are the advantages of the Tillman-Olsen method? What are modifications that can be made?

  • Advantages
    • Standardized procedure
    • Removes tester bias
    • Highly reliable
  • Modifications
    • ​Same preliminary
    • Can use 5 dB steps, with 5 words on a step
    • Stop when they get 5 words wrong
    • Correction factor = 2dB 

A image thumb
9

Describe the current SRT method. What did Jahner, Schlauch and Doyle compare? Wht is the ASHA '79 method? How do the methods differ?What were their results? What was their conclusion?

  • Jahner, Schlauch, & Doyle, 1994
    • Compared ASHA ‘79 and T-O methods for measuring SRT
      • S’s were 30 veterans with hearing loss
      • ASHA, ‘79 method: comparable to Hughson-Westlake method of pure tone testing
      • T-O - descending, ASHA '79 - ascending
    • Results
      • SRT with T-O method < ’79 method by 4 dB
      • ASHA ’79 method agreed better with PTA and took less time to perform
    • Conclusion: for clinical purposes, two methods are similar

10

What are some variables influencing the measurement of SRTs? 

  • Descending vs. ascending method: not significant (n.s.) for cooperative patients
  • step size (2 dB  vs. 5 dB): n.s.
  • carrier phrase vs. no carrier phrase: n.s.
  • Recorded vs. MLV
    • MLV: widely used (flexible for kids & elderly)
    • MLV: difficult to peak at 0 VU
    • Will influence test results
    • Results are reliable if same tester
    • To use standardized procedure – must use recorded materials
  • Effect of prior knowledge of vocabulary and practice effects
    • Improvement in SRT due to practice: 1 dB
      • Tested twice with a week in between and different words
    • Improvement in SRT due to practice and possible prior knowledge: 2.4 dB
      • Tested twice with a week in between with same words
    • Improvement in SRT due to prior knowledge of vocabulary: 6 dB
      • Familiarized the words first, and again a week later
    • Conclusion: practice doesn’t influence θs too much, but prior knowledge does
    • Recommend: familiarization of vocabulary

11

What is the relationship between speech and pure tone thresholds?

  • Comparison using SPL scale - not linear with SRT
    • SRT = 20 dB SPL
    • PTA = 11.5 + 7 + 9 dB SPL = 9 dB SPL
  • Comparison using HL scale:
    • θ for speech ≈ θ for pure tones
    • Linear slope ≈ 1

12

What are the methods to calculate PTA?

  • Fletcher (1929): 3-freq’y PTA
    • Average θ for .5,1,2 kHz – used as predictor of speech θ
  • Carhart (1946)  
    • Correlation between PTA and SRT depends on audiogram configuration
    • r = .79 (flat); r = .75 (gradually sloping); r = .29 (sharply sloping audiograms)  
    • better SRT than PTA because speech is concentrated in low frequencies
  • Fletcher (1950): use average of best 2 θs in 500-2k range, as predictor of SRT (FA)
    • Works best when applied to sloping audiogram
  • Use PTA or FA, depending on slope of audiogram
     

13

What is the acceptable agreement between PTA ans SRT?What are reasons for lack of agreement?

  • Acceptable agreement between PTA and SRT: +/- 6 dB -> +/-12 dB
  • Reasons for lack of agreement:
    • SRT< PTA
      • Sharply sloping audiogram - good low frequency hearing
      • Pseudohypacusis/functional hearing loss
        • functional hearing loss - hearing loss without organic basis
          • malingering
            • Would be better because people have an internal loudness reference - when signal gets "x" loud I'll respond
            • Growth of loudness for speech grows (BW) more quickly than for pure tones
              • Will reach their reference sooner than for pure tones
          • psychological trauma
    • PTA
    • Central disorder, speech, or language problem  - not responding well to speech
    • Severe discrim problem (N. VIII disorder)
      • Shouldnt happen if only problem is hearing loss because throw words out
    • Developmental age
    • Cognitive disorder
       

14

Describe Schlauch's study of identification of functional hearing loss. What were the 4 groups? What were the results?

  • Compared 4 screening procedures for FHL
  • tested 120 S’s feigning a loss, used bandpass noise to mimic speech; assigned to 4 groups
    • 1 . Noise-band group : measured ascending band-pass noise Θs vs. descending tonal Θs
    • 2 . Spondee group : ascending spondee Θs (STs) vs. descending tonal Θs (.5k and 1k Hz)
    • 3 . Two-tone group : ascending vs. descending tonal Θs at 5kHz and 1kHz
    • 4 . Three-tone group : same as 2-tone but w/ .5, 1, and 2kHz
  • Results: spondee & 2-tone screening procedure + re-test at 1k Hz yields 100% hit rate and 0% false + rate (difference always > 10 dB)

15

What is the definition of SDT? What is the relationship between SDT and SRT? When is SDT used? What is the relationship between SDT and pure tone thresholds?

  • Definition: lowest intensity level at which individual can just detect the speech stimulus
  • Recall: SDT< SRT by 8-9 dB
  • use SDT when person can’t repeat spondees:
    • Young children
    • Individual with severe discrim problem
  • relationship between SDT and pure tone thresholds: agrees with best θ on audiogram between 250 and 4000 Hz
     

16

Describe speech thresholds and bone conduction. Who is it useful with? What can be compared? How is the bone oscillator callibrated for speech?

  • Speech stimuli can be presented via b.c. vibrator
  • Useful for patients who don’t respond well to pure tones (kids)
  • Compare SRT via a.c. and b.c. (a-b gap)
  • calibration of bc oscillator for speech:
    • Use S’s with normal hearing or sn hrg loss
    • Determine SRT via a.c., & adjust b.c. oscillator so that SRT via b.c. is the same
       

17

What procedures can be used with school aged children? Who needs modifications to these procedures? why?

  • Special needs of children
  • Procedures for adults are OK with schoolaged children  
  • Need to modify these techniques for younger children or multiply-handicapped kids because:
    • Limited  vocabulary
    • Limited expressive skills
    • Short attention span

18

What materials are used with a pediatric population? How are they depicted? What is this helpful with? What is done before the test?

  • Materials for a pediatric population
    • Use selected spondees within the child’s vocabulary
    • Published in ASHA, 1988 (ice cream, etc.)
    • Use pictures or toys depicting spondees (for picture-pointing response)
      • Helpful for kids with limited expressive skills
      • Screen child before test to make sure he/she can pick out the pictures correctly
         

19

What methods are used with children? What are conditioning techniques? What if you can't condition the child?

  • Methods
    • picture pointing
      • Limit set to 12 or less (visual scan, memory load)
      • Familiarize child with stimuli prior to test (A+V)
      • Use carrier phrase (“show me”)
      • Work in 5-dB steps, rather than 2-dB steps (faster)
    • conditioning techniques: if limited vocabulary
      • Use VRA
      • Obtain MRL in SF – reflects hearing in better ear
    • alerting response: if you can’t condition child
      • Use ascending method; note lowest level of response
         

20

Why is it important to establish SDT or SRTs in children?

  • Importance of establishing SDT or SRT in children
    • Easier to establish than p.t. θs
    • Indicates validity of p.t. θs
    • Helps pick up children who are malingering