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Sound Field Testing

Sound Field Testing

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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!