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Sound Field Testing

Sound Field Testing. MCHAS TEAM. Wave 4 SFR 17/05/04. What can aided sound field thresholds tell us?. 10. 0. 10. 20. 30. 40. 50. 60. 70. 80. 90. 100. 110. 120. 130. 140. 125. 250. 500 1000 2000. 4000. 8000. Frequency (Hz). Aided Thresholds.

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Sound Field Testing

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  1. Sound Field Testing MCHAS TEAM Wave 4 SFR 17/05/04

  2. What can aided sound field thresholds tell us?

  3. 10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 125 250 500 1000 2000 4000 8000 Frequency (Hz) Aided Thresholds A A A A A

  4. Limitations • Relies on valid behavioural response

  5. 10 0 10 20 A 30 A A 40 A 50 Hearing Threshold 60 70 80 90 100 110 120 130 140 .125 .25 .5 1 2 4 8 Frequency (Hz) Limitations • Limited frequency resolution VS

  6. 140 130 120 110 100 90 80 70 dB SPL (TM) 60 50 40 30 20 10 0 -10 125 250 500 1000 2000 4000 8000 Frequency (Hz) Limitations • No information on real ear output characteristics HA X X X X X X A A A A

  7. 10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 125 250 500 1000 2000 4000 8000 Frequency (Hz) Limitations • Poor test-retest reliability • Need at least 15 dB difference between conditions before significant effect (Hawkins 1985). A A A A A A A A A A

  8. Limitations • Provide little indication of speech audibility, especially when using WDRC. Seewald 2003

  9. 10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 125 250 500 1000 2000 4000 8000 Frequency (Hz) Limitations • Inaccurate in regions of normal hearing X X A A A A A A X X X X

  10. So………… what information is provided? • An indication of the child’s/infant’s auditory performance • Good visual/auditory demonstration to parents between ‘no hearing aids’ vs ‘hearing aids’.

  11. A word of caution • Be aware of possible interactions with hearing aid features. • Number of channels • Compression speed • Noise algorithms • Active feedback control

  12. What the Aided Threshold is and is not • IS: -index to reflect softest perceptible sound w/o vc -Functional gain reflects gain for softest sound (not conversational level) • IS NOT: -Reflect gain for any input level other than soft -Reflect gain for conversational sounds -Reflect loudness comfort -Reflect processing of DSP aids eg. NR etc Kuk, F (AAA 2004)

  13. What Real-Ear Measure is and is not • IS:-Allows determination of physical output of hearing aid at different input levels: *Gain for conversational, soft and loud sounds *Effect of signal processing eg.compression, NR etc • IS NOT:-A perceptual response ie. Does not tell how soft a child can hear -cannot predict aided threshold Kuk, F (AAA 2004)

  14. So, should we be using both for a fuller picture? • Perhaps • If so, what should be the optimal aided threshold? • Depends on criteria: *Importance of hearing soft or low level input sounds and meaningfulness of these *Degree of hearing loss and possible dead regions *Limitations of hearing aid (as discussed)

  15. THANK-YOU!

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