Mild Hearing Loss is Serious Business - PowerPoint PPT Presentation

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Mild Hearing Loss is Serious Business

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  1. Mild Hearing Loss is Serious Business Harvey Dillon Sharon Cameron, Teresa Ching, Helen Glyde, Gitte Keidser, David Hartley, Jorge Mejia NAL, The Hearing CRC IHCON, 2010

  2. Slides on the NAL web site: www.nal.gov.au

  3. What is mild hearing loss? • Four-frequency average (500, 1000, 2000, 4000 Hz) hearing loss in better ear between 20 and 40 dB HL • Self-reported disability or handicap within a certain range • SRT in noise loss of between 3 and 6 dB

  4. 4FAHL or 3FAHL?

  5. How prevalent is mild hearing loss?

  6. How prevalent is mild hearing loss? • Davis (1995): 16% of adult population • Wilson (1990): 18% of adult population • Hartley et al (in press): 34% of people aged > 50 years

  7. Blue Mountains 4FAHL better ear Hartley et al (in press)

  8. Aging population - Australia

  9. Population aging, worldwide

  10. Mild losses for study ~ Minimum loss eligible for government benefits Mild loss (4FA=29 dB) Mild-mod loss (4FA=39 dB) ~ Median loss newly fitted in Australia

  11. Mild losses for study 4FA HL Mild 9 dB Mild-mod 39 dB Moderate 49 dB Mod-Sev 59 dB Severe 69 dB

  12. How common is hearing aid use amongst those with mild hearing loss?

  13. Penetration by hearing loss • Penetration as a function of hearing loss • Davis (1995) • Wilson et al (1998) • Hartley et al (in Press) • Kochkin consistent

  14. Aid ownership by hearing lossBlue Mountains Population >55 years Hartley et al (in Press)

  15. What are the characteristics of mild hearing loss?

  16. Characteristics of mild loss • Threshold elevation √ • Loss of OHC/OAE • Loss of frequency resolution – TEN, PTC, FRI • Loss of temporal (envelope) resolution • Loss of fine temporal information • Loss of spatial processing • Loss of SRT in noise • Increased disability and handicap

  17. Loss of active process in cochlear:OHC and OAE

  18. FRI A A f f Ching & Dillon (unpublished data) Loss of frequency resolution

  19. Frequency resolution

  20. A TRI t t Loss of temporal resolution

  21. Temporal resolution Ching & Dillon (unpublished data)

  22. Loss of fine temporal information • 20 synapses per IHC • Synapse loss or IHC loss  reduced averaging  temporal jitter Inspiration: • Bodian, Lieberman, Moore, Pichora-Fuller, Spoendlin,

  23. A digression into “normal” hearing

  24. Spatial Processing Disorder Speech Sharon Cameron Noise Noise Noise Noise 26

  25. Listening in Spatialised Noise - Sentences(LiSN-S) Conditions Total Advantage Talker Advantage Spatial Advantage Same voices Different voices Same direction Low Cue Different directions High Cue Cameron & Dillon (2009)

  26. LiSN-S Diagnostic Screen

  27. Spatial Advantage(≡ Spatial Release from Masking) Nth America Australia Better

  28. Spatial Advantage Better

  29. Results profile: spatial processing disorder

  30. Spatial processing remediation Pre vs. Post (n=9) LC SRT - p = 0.158 Talker Advantage - p = 0.981 HC SRT - p = 0.0002 Spatial Advantage - p = 0.0002 Total Advantage - p = 0.001

  31. Application to people with hearing loss

  32. Spatial hearing loss in hearing-impaired people:LiSN-S Prescribed Gain Amplifier

  33. Deficit in SRTn with hearing loss R = -0.87 P = 0.000006 Cameron, Glyde & Dillon, unpublished data)

  34. Cause of deficit in SRTn R = -0.86 P = 0.00001 Cameron, Glyde & Dillon, unpublished data)

  35. Talker advantage deficit versus age Cameron, Glyde & Dillon, unpublished data)

  36. ILD ITD SO / IC / A1 ~ Sensorineural hearing loss CN CN Binaural processing Executive control CAPD x x ILD ITD R L

  37. Loss of SNR in understanding speech “Basic” loss of 0.6 dB per 10 dB of loss + Loss of Spatial release from masking of 2.3 dB per 10 dB of loss + Loss of Talker cue release from masking of 0.5 dB per 10 years of age

  38. 1 dB / 10 dB 1.8 dB / 10 dB Loss of SRT in noise Commonly 1.5 dB increase in SNR per 10 dB of hearing loss SNR = -4 dB Carter, Zhou & Dillon, unpublished data)

  39. Should mild hearing loss interfere with speech perception?

  40. SNR Speech and noise levels Source: Pearsons, Bennett and Fidell (1977)

  41. Calculation of SII Noise = 60 dBA Speech = 64 dBA SIInh=0.65 SIIhi=0.46

  42. 20 40 60 80 100 Effective audibility

  43. Transfer functionSII  Percent correct

  44. Mild losses for study Mild loss (4FA=29 dB) Mild-mod loss (4FA=39 dB)

  45. Predicted speech intelligibility Greatest problems in noisy places !!

  46. Predicted variation of SRTn with hearing loss Modified SII model predicts only 0.4 dB loss per 10 dB of hearing loss Speech level

  47. Modification of SII • Assume normal hearers get 6 dB advantage from spatial separation of speech and noise • Assume hearing impaired listeners lose spatial advantage at a rate of 1.3 dB per 10 dB of loss (above SII predictions)  total loss of SNR is 1.7 dB per 10 dB of loss

  48. Calculation of intelligibility Speech spectrum Sensation Level Effective audibility Noise spectrum SII (Information received) Percent correct Max Importance function Threshold

  49. current ^ Do hearing aids help people with mild hearing loss?