1. HEARLab training Harvey Dillon, Bram Van Dun, Lyndal Carter, Kirsty Gardner-Berry HEARing CRC National Acoustic Laboratories (NAL) www.hearingcrc.org With thanks to John Seymour, Suzanne Purdy, Maryanne Golding, Hsiuwen Chang, Barry Clinch, Lars Kirk 3 September 2010 - Version 1 NAL : Dillon, Van Dun, Carter, Gardner-Berry

2. INTRODUCTION

3. The need for a new measurement tool NAL : Dillon, Van Dun, Carter, Gardner-Berry

4. Evaluation of aided functioning in infants Universal new born screening Early fitting of hearing aids Need for an evaluation method Confirmation of fitting Fine-tuning needed Cochlear implant needed NAL : Dillon, Van Dun, Carter, Gardner-Berry

5. So baby, how does it sound? Objective hearing aid evaluation for: young infantsyoung infants difficult-to-test peopledifficult-to-test people NAL : Dillon, Van Dun, Carter, Gardner-Berry

6. Why the rush? Language ability 6 months after implantation NAL : Dillon, Van Dun, Carter, Gardner-Berry

7. Significant effect of age of fitting: p = 0.001* Early intervention leads to better language development at 6 months after fitting (n=90) NAL : Dillon, Van Dun, Carter, Gardner-Berry

8. Why use cortical responses? NAL : Dillon, Van Dun, Carter, Gardner-Berry

9. Why cortical responses to evaluate hearing aid fitting in infants? Reliably present in awake young infantsReliably present in awake young infants More likely to correlate well with perceptionMore likely to correlate well with perception Can be elicited by a range of speech phonemes – close to desired outcomesCan be elicited by a range of speech phonemes – close to desired outcomes Stimuli handled reasonably by hearing aidsStimuli handled reasonably by hearing aids Can be very frequency specific if neededCan be very frequency specific if needed NAL : Dillon, Van Dun, Carter, Gardner-Berry

10. FUNDAMENTALS OF CORTICAL RESPONSES NAL : Dillon, Van Dun, Carter, Gardner-Berry

11. Auditory Brainstem Response Cortical Response Baer, 2003

12. The end of the road NAL : Dillon, Van Dun, Carter, Gardner-Berry

13. Auditory cortex orientation NAL : Dillon, Van Dun, Carter, Gardner-Berry

14. Auditory cortex orientation NAL : Dillon, Van Dun, Carter, Gardner-Berry

15. Auditory cortex orientation

16. Hudson, 2009 + - + NAL : Dillon, Van Dun, Carter, Gardner-Berry

17. Cortical responses in adults with normal hearing NAL : Dillon, Van Dun, Carter, Gardner-Berry

18. Adult 2.5 5.0 300400 µV 0 100200 500 600 0.0 -2.5 P2 N1 P1 NAL : Dillon, Van Dun, Carter, Gardner-Berry

19. Adult grand mean waveforms at Cz Tones Speech NAL : Dillon, Van Dun, Carter, Gardner-Berry

20. Cortical responses in infants with normal hearing NAL : Dillon, Van Dun, Carter, Gardner-Berry

21. Infants ms 500600300400100200-1000 µV 0 5 10 -5 P N NAL : Dillon, Van Dun, Carter, Gardner-Berry

22. /t/ black /g/ blue /m/ green 500 Hz red 2000Hz pink Infant CAEPs to various stimuli NAL : Dillon, Van Dun, Carter, Gardner-Berry

23. Repeated measures ANOVA (N= 20) stimulus (p<.0001), montage (n.s.), stimulus x montage (p=0.0223) P1 Latency NAL : Dillon, Van Dun, Carter, Gardner-Berry

24. P1 amplitude Repeated measures ANOVA (N= 20) stimulus (p<.0001), montage (p = 0.0006), stimulus x montage (n.s.) NAL : Dillon, Van Dun, Carter, Gardner-Berry

25. Latency versus age Sharma et al NAL data NAL : Dillon, Van Dun, Carter, Gardner-Berry

26. HEARLAB: TECHNICAL OVERVIEW NAL : Dillon, Van Dun, Carter, Gardner-Berry

27. Practical implementation of cortical testing: HEARLab Disclosure: NAL will get a royalty for each unit sold. Thank you: The HEARLab development team – Teck Loi, Barry Clinch, Isabella Tan, Ben Rudzyn, Lyndal Carter, Dan Zhou, Scott Brewer NAL : Dillon, Van Dun, Carter, Gardner-Berry

29. 1.Electrodes HEARLab active electrodes Poor electrode contact leads to poor quality responses NAL : Dillon, Van Dun, Carter, Gardner-Berry

30. In combination with: Ambu Blue Sensor N disposable electrodes

31. 2. Differential Amplification Two electrodes detect the “response (signal)” to varying degrees plus “noise”, with reference to a third electrode, By inverting the electrical activity at one of the two main sites, and finding the difference between them, some noise cancellation occurs and the signal size is increased, This improves the signal-to-noise ratio (SNR) to some degree. NAL : Dillon, Van Dun, Carter, Gardner-Berry

32. 2. Differential amplification Inverting Non-inverting + - Ground NAL : Dillon, Van Dun, Carter, Gardner-Berry From: Hall, J.W. (1992) Handbook of Auditory Evoked Potentials (Excerpts from Figure 5-13) Electrode input:+-Ground Pre-ampActiveReferenceGround Non-invertingInvertingReference

33. 3. Averaging Averaging is the single most powerful technique for improving SNR For repeated auditory stimulation, the neurons of the auditory system will be activated in the same sequence, at the same point in time, We can say then that this neuronal activity is “time-locked” to the presentation of the stimulus. NAL : Dillon, Van Dun, Carter, Gardner-Berry

34. 3. Averaging NAL : Dillon, Van Dun, Carter, Gardner-Berry

35. Repeated stimulation with the same sound is required to view the auditory response (i.e., to have an adequate signal-to-noise ratio), The number of stimulations required depends on the size (i.e., amplitude) of the response. 3. Averaging NAL : Dillon, Van Dun, Carter, Gardner-Berry

36. 4. Filters A device which permits some frequencies through and not others, High Pass (low freq) filters reject lower energy and Low Pass (high freq) reject energy above. The most appropriate filters are those which preserve the frequency region of the response and exclude others NAL : Dillon, Van Dun, Carter, Gardner-Berry

37. 4. Filters NAL : Dillon, Van Dun, Carter, Gardner-Berry

38. Choice of stimulus depends on our clinical objective and from where in the auditory system we are recording. Responses from the early parts of the auditory system are best generated using very brief stimuli such as a “click”. Responses from late in the auditory system can be generated using tones, speech sounds or clicks. Stimuli may be delivered by headphone, insert earphone, bone conduction or loud speaker. 5. Stimuli NAL : Dillon, Van Dun, Carter, Gardner-Berry

39. Three speech sounds: /m/ /g/ /t/ 5. Stimuli NAL : Dillon, Van Dun, Carter, Gardner-Berry

40. Automatic detection of cortical responses NAL : Dillon, Van Dun, Carter, Gardner-Berry

41. Why automated method? variable shape across agesvariable shape across ages variable shape with auditory experiencevariable shape with auditory experience variable shape from person to personvariable shape from person to person variable shape from time to time (state of person, especially sleepiness)variable shape from time to time (state of person, especially sleepiness) variable shape with stimulusvariable shape with stimulus Variable shape with inter-stimulus intervalVariable shape with inter-stimulus interval high skill level needed to read responses NAL : Dillon, Van Dun, Carter, Gardner-Berry

42. Desirable characteristics No reliance on a templateNo reliance on a template Able to use information from contributing portions of waveformAble to use information from contributing portions of waveform Able to discount non-contributing portions of waveformAble to discount non-contributing portions of waveform Hotellings T 2 NAL : Dillon, Van Dun, Carter, Gardner-Berry

43. Each response* is divided into 50 ms time bins (50 – 500 ms)Each response* is divided into 50 ms time bins (50 – 500 ms) The data points are averaged within each time bin to form 9 variablesThe data points are averaged within each time bin to form 9 variables Time Voltage Response detection (Hotelling’s T 2 ) Stim onset NAL : Dillon, Van Dun, Carter, Gardner-Berry

44. Calculates the probability that a mean value of any linear combination of the 9 variables was significantly different from zero. Hotelling’s T 2 is : At least equal to, if not more able, than the “composite” examiner to differentiate a CAEP from random noise at sensation levels of 10 dB or more Response detection (Hotelling’s T 2 ) NAL : Dillon, Van Dun, Carter, Gardner-Berry

45. Effect of sensation level, hearing loss, and unrelated EEG or muscle noise NAL : Dillon, Van Dun, Carter, Gardner-Berry

46. Residual noise levels (for 100 epochs) 0 5 Awake adults Awake infants But also larger responses NAL : Dillon, Van Dun, Carter, Gardner-Berry

47. Growth of amplitude with SL Normal hearing infants Normal hearing adults Hearing impaired adults Hearing impaired infants NAL : Dillon, Van Dun, Carter, Gardner-Berry

48. Conclusions: Detecting cortical response presence Large responses are more easily detectedLarge responses are more easily detected Response amplitude grows with sensation levelResponse amplitude grows with sensation level Response amplitude at low SL is larger for people with sensorineural hearing loss that for people with normal hearingResponse amplitude at low SL is larger for people with sensorineural hearing loss that for people with normal hearing Responses are more easily detected when residual noise is low (<3.4 µV for infants; < 1.5 µV for adults)Responses are more easily detected when residual noise is low (<3.4 µV for infants; < 1.5 µV for adults) NAL : Dillon, Van Dun, Carter, Gardner-Berry

49. CLINICAL USE OF HEARLAB NAL : Dillon, Van Dun, Carter, Gardner-Berry

50. Equipment configuration and test environment NAL : Dillon, Van Dun, Carter, Gardner-Berry

51. Equipment configuration NAL : Dillon, Van Dun, Carter, Gardner-Berry

52. Equipment configuration NAL : Dillon, Van Dun, Carter, Gardner-Berry

53. CAEP room set-up at the National Acoustic Laboratories Free Field Speaker Baby sits on parent’s lap in the centre of the room or in a high chair. NAL : Dillon, Van Dun, Carter, Gardner-Berry

54. Calibration Calibrate each time major changes occur in test environment. For details refer to HEARLab manual, Section 4.1 NAL : Dillon, Van Dun, Carter, Gardner-Berry

55. Ambient noise measurement In general the ambient noise level should not exceed 35 dB A. For details refer to HEARLab manual, Section 5.3.3 NAL : Dillon, Van Dun, Carter, Gardner-Berry

56. Test environment NAL : Dillon, Van Dun, Carter, Gardner-Berry (highlights from HEARLab manual, Appendix A: ‘Practical aspects of CAEP testing with infants’) Make the test environment ‘child friendly’. Provide a chair that is big enough for both parent and child. Use washable covers/towels on the chair. Have a separate container on hand to collect items that require cleaning. Avoid fluorescent lighting, cell phones. Do not place mains-powered devices close to the child. Place floor markers indicating the position of equipment after calibration.

57. Before the appointment NAL : Dillon, Van Dun, Carter, Gardner-Berry

58. Before the appointment NAL : Dillon, Van Dun, Carter, Gardner-Berry (highlights from HEARLab manual, Appendix A: ‘Practical aspects of CAEP testing with infants’) Provide parents with information. This will save time during the assessment. Ask about the child’s sleeping routines. They should be awake during testing. Dress the child with layers of clothing that can be easily removed.

59. Preparation for testing NAL : Dillon, Van Dun, Carter, Gardner-Berry

60. From: Hall, J.W. (1992) Handbook of Auditory Evoked Potentials NAL : Dillon, Van Dun, Carter, Gardner-Berry

61. Electrode equipment NAL : Dillon, Van Dun, Carter, Gardner-Berry

62. Keeping electrodes on the baby using a headband NAL : Dillon, Van Dun, Carter, Gardner-Berry

63. Preparation for testing NAL : Dillon, Van Dun, Carter, Gardner-Berry (highlights from HEARLab manual, Appendix A: ‘Practical aspects of CAEP testing with infants’) Have all equipment ready before the child arrives. Change hearing aid batteries and check operation. Ask parents to switch off mobile phones. Connect to the child and don’t physically ‘stand over’ the child while doing skin prep. Prepare the skin firmly but not too hard with cotton bud and medical gel. Alcohol wipes is not needed and not recommended for delicate infant skins. A headband can be very helpful for keeping electrodes in place. Avoid contact of electrode cables with child as (s)he may pull them away.

64. Conducting a measurement NAL : Dillon, Van Dun, Carter, Gardner-Berry

65. HEARLab NAL : Dillon, Van Dun, Carter, Gardner-Berry Two options:  ACA: “Aided Cortical Assessment” Free field Speech sounds Can be tested aided or unaided Focused on infants  CTE: “Cortical Threshold Evaluation” With insert phones Tone-bursts Only unaided Focused on adults

66. Starting up HEARLab NAL : Dillon, Van Dun, Carter, Gardner-Berry Double click icon First screen that pops up: More detailed information in HEARLab manual, Chapter 3.

67. Adding a new client NAL : Dillon, Van Dun, Carter, Gardner-Berry

68. Searching for a client

69. NAL : Dillon, Van Dun, Carter, Gardner-Berry New assessment

70. NAL : Dillon, Van Dun, Carter, Gardner-Berry Configuring ACA

71. NAL : Dillon, Van Dun, Carter, Gardner-Berry Configuring ACA

72. NAL : Dillon, Van Dun, Carter, Gardner-Berry New run

73. NAL : Dillon, Van Dun, Carter, Gardner-Berry Impedance check

74. NAL : Dillon, Van Dun, Carter, Gardner-Berry Acquisition of data

75. NAL : Dillon, Van Dun, Carter, Gardner-Berry Acquisition of data

76. Ongoing EEG Most recent epoch Cumulative averages p-value automatic detection NAL : Dillon, Van Dun, Carter, Gardner-Berry

77. Acquisition of data p-value automatic detection Residual noise level The indicator lights should be GREEN p-values must be < 0.05 for detection of cortical ! This means that in 5% of the cases a false detection is possible !

78. NAL : Dillon, Van Dun, Carter, Gardner-Berry Result window

79. NAL : Dillon, Van Dun, Carter, Gardner-Berry Result window Were responses detected? Averaged responses Statistical analysis history

80. Distraction techniques NAL : Dillon, Van Dun, Carter, Gardner-Berry (highlights from HEARLab manual, Appendix A: ‘Practical aspects of CAEP testing with infants’) Do not obstruct the line of sight to the loudspeaker when testing free field. Only use noiseless toys, appropriate to the age, and which are easily cleanable. Try to keep children awake, but not too active. DVDs on a screen! Bubbles! Following slides will show a lot of distraction items. Eating and drinking is possible, including breast feeding. If the child is quiet, the distractor can move out of sight.

81. Keeping the baby awake! NAL : Dillon, Van Dun, Carter, Gardner-Berry

82. Tools for keeping baby quiet, alert, awake NAL : Dillon, Van Dun, Carter, Gardner-Berry

83. (More) tools for keeping baby quiet, alert, awake NAL : Dillon, Van Dun, Carter, Gardner-Berry

84. (Yet more) tools for keeping baby quiet, alert, awake NAL : Dillon, Van Dun, Carter, Gardner-Berry

85. Yes!! NAL : Dillon, Van Dun, Carter, Gardner-Berry Head support

86. Cortical threshold estimation - is very similar to ACA - has not been verified clinically with infants yet NAL : Dillon, Van Dun, Carter, Gardner-Berry

87. Finishing up NAL : Dillon, Van Dun, Carter, Gardner-Berry

88. Finishing up NAL : Dillon, Van Dun, Carter, Gardner-Berry Results can be printed. Follow infection guidelines to wash or dispose of used equipment.

89. INTERPRETATION OF THE RESULTS & CLINICAL APPLICATIONS NAL : Dillon, Van Dun, Carter, Gardner-Berry

90. Estimating hearing thresholds in non-responsive adults Elderly infirm – stroke, dementia Workers’ compensation NAL : Dillon, Van Dun, Carter, Gardner-Berry

91. Good agreement between CAEP and audiometric thresholds in awake adults Tsui, Wong & Wong 2002 NAL : Dillon, Van Dun, Carter, Gardner-Berry

92. Cortical threshold vs behavioural threshold - adults NAL : Dillon, Van Dun, Carter, Gardner-Berry outliers in about 7% of threshold estimates! (reported by several studies)

93. Cortical thresholds minus Behavioral thresholds 68% +5 dB 84% +10 dB 91% +15 dB NAL : Dillon, Van Dun, Carter, Gardner-Berry

94. Conclusions: Estimating behavioural thresholds in hearing-impaired adults Cortical thresholds overestimate behavioural thresholds by 2.4 dB, on averageCortical thresholds overestimate behavioural thresholds by 2.4 dB, on average Standard deviation of cortical – behavioural threshold differences is 6.3 dBStandard deviation of cortical – behavioural threshold differences is 6.3 dB About 7% overestimates hearing thresholds severely (by 20 dB or more).About 7% overestimates hearing thresholds severely (by 20 dB or more). Applications: hearing compensation, clients unable to respondApplications: hearing compensation, clients unable to respond NAL : Dillon, Van Dun, Carter, Gardner-Berry

95. Cortical potentials to assess speech audibility for infants NAL : Dillon, Van Dun, Carter, Gardner-Berry

96. Clinical implications of corticals Significant response is obtained to speech at 65 dB SPL No significant response is obtained to speech at 65 dB SPL or to speech at 75 dB SPL Morphology normal for age Morphology abnormal for age Low residual noise High residual noise All is well Repeat test Re-check fitting; Consider all options Draw no conclusion ! NAL : Dillon, Van Dun, Carter, Gardner-Berry

97. Noisy results - chewing NAL : Dillon, Van Dun, Carter, Gardner-Berry

98. Clinical implications of corticals (cont) No /t/ response Draw no conclusions from missing response ! Mixed results (and noise is low) No /g/ response No /m/ response Review HF gain or loss estimate Review mid-freq gain or loss estimate Mixed results (and noise is high) Review LF gain or loss estimate NAL : Dillon, Van Dun, Carter, Gardner-Berry

99. Hearing loss at birth ….. for parents Parental denial Working towards a solution Pessimism and hopelessness Unaided testing at conversational levels Aided testing at conversational levels NAL : Dillon, Van Dun, Carter, Gardner-Berry

100. Detection of corticals in infants However, some caution is recommended. For speech sounds exceeding 10 dB Sensation Level  23% of evoked corticals are NOT present / detected This means that any audiological decisions should not be made based on cortical measurements alone! NAL : Dillon, Van Dun, Carter, Gardner-Berry

101. CASE STUDIES NAL : Dillon, Van Dun, Carter, Gardner-Berry

102. Case 1 Age at aided cortical testing –Visit 1 6 weeks old (Initial hearing aid fitting day) –Visit 2 3 months old No cortical responses, and the results helped the parents accept the need for cochlear implants NAL : Dillon, Van Dun, Carter, Gardner-Berry

103. Tone-burst ABR (Estimated levels in dB nHL) 500 Hz1000 Hz2000 Hz4000 Hz Right>95 Left>95 Estimated Audiogram (dB HL) at Visit 1 500 Hz1000 Hz2000 Hz4000 Hz Right859095 Left859095 Estimated Audiogram (dB HL) at Visit 2 500 Hz1000 Hz2000 Hz4000 Hz Right90100105 Left90100105 NAL : Dillon, Van Dun, Carter, Gardner-Berry

104. Visit 1 Increase gain at all frequencies P < 0.05 ? …. No NAL : Dillon, Van Dun, Carter, Gardner-Berry

105. Visit 2 NAL : Dillon, Van Dun, Carter, Gardner-Berry

106. The infant received bilateral cochlear implants at 5 months of age. Email from the baby’s parents ~ “Thank you so much for the information you gave us on the previous testing as it helped us with our decision to proceed with the implants.” NAL : Dillon, Van Dun, Carter, Gardner-Berry

107. Case 2 Age at aided cortical testing –Visit 1 13 weeks old –Visit 2 17 weeks old –Visit 3 21 weeks old Hearing aid fitting at 8 weeks of age No cortical responses, even after hearing aids have been increased in gain for the third time and the parents don’t want a cochlear implant for their baby NAL : Dillon, Van Dun, Carter, Gardner-Berry

108. Estimated Audiogram (dB HL) at Visit 1 500 Hz1000 Hz2000 Hz4000 Hz Right9080 85 Left8575 95 Estimated Audiogram (dB HL) at Visit 2 500 Hz1000 Hz2000 Hz4000 Hz Right10090 95 Left9585 95 Estimated Audiogram (dB HL) at Visit 3 500 Hz1000 Hz2000 Hz4000 Hz Right100 Left100 NAL : Dillon, Van Dun, Carter, Gardner-Berry

109. Visit 1 Increase gain at all frequencies NAL : Dillon, Van Dun, Carter, Gardner-Berry

110. Visit 2 Right aidedLeft aided Increase gain at all frequencies NAL : Dillon, Van Dun, Carter, Gardner-Berry

111. Visit 3 NAL : Dillon, Van Dun, Carter, Gardner-Berry

112. The parents still believe that their baby boy can be oral by using hearing aids. They are hoping to see that their baby can benefit from more powerful hearing aids. The baby’s hearing aids were changed from Siemens Explorer 500 P to Phonak Una SP after Visit 3. NAL : Dillon, Van Dun, Carter, Gardner-Berry

113. Case 3 Age at aided cortical testing –Visit 1 4.5 months old –Visit 2 5.5 months old Hearing aid fitting at 5 weeks of age Corticals provided reassurance about the baby hearing well NAL : Dillon, Van Dun, Carter, Gardner-Berry

114. Tone-burst ABR (Estimated levels in dB nHL) 500 Hz1000 Hz2000 Hz4000 Hz Right40DNT6070 Left40DNT7080 Estimated Audiogram (dB HL) at Visit 1 500 Hz1000 Hz2000 Hz4000 Hz Right30405565 Left30456575 Estimated Audiogram (dB HL) at Visit 2 500 Hz1000 Hz2000 Hz4000 Hz Right40455565 Left40506575 NAL : Dillon, Van Dun, Carter, Gardner-Berry

115. Visit 1 Increase low- and mid- frequency gain NAL : Dillon, Van Dun, Carter, Gardner-Berry

116. Visit 2 NAL : Dillon, Van Dun, Carter, Gardner-Berry

117. Email from mother: “We feel very relieved, as our faith has been restored in the hearing aids as a result of what we discovered from the results.” NAL : Dillon, Van Dun, Carter, Gardner-Berry

118. Case 4 Age at aided cortical testing –Visit 1 8 months old –Visit 2 9 months old Hearing aids have been increased in gain two weeks before the second visit. Hearing aid fitting at 9 weeks of age Too few significant cortical responses, and the aid gain was increased, resulting in more cortical responses NAL: Dillon, Van Dun, Carter, Gardner-Berry

119. Estimated Audiogram (dB HL) at Visit 1 500 Hz1000 Hz2000 Hz4000 Hz Right455055 Left45556555 Estimated Audiogram (dB HL) at Visit 2 500 Hz1000 Hz2000 Hz4000 Hz Right555055 Left55 6555 NAL: Dillon, Van Dun, Carter, Gardner-Berry

120. Visit 1 Visit 2 NAL: Dillon, Van Dun, Carter, Gardner-Berry

121. Case 5 Age at testing: 4.5 years Multiple disabilities A reliable behavioural audiogram has not yet been obtained. A case where cortical testing was not possible NAL: Dillon, Van Dun, Carter, Gardner-Berry

122. She was moving all the time. NAL : Dillon, Van Dun, Carter, Gardner-Berry

123. At her quietest state, but this only lasted for a few seconds. NAL: Dillon, Van Dun, Carter, Gardner-Berry

124. Cortical testing at 8 months of age, nine days after the initial hearing aid fitting A case where the unaided /m/ was present but the aided /m/ was absent. NAL: Dillon, Van Dun, Carter, Gardner-Berry Case 6

125. Estimated Audiogram 500 Hz1000 Hz2000 Hz4000 Hz Right40354045 Left40354045 NAL: Dillon, Van Dun, Carter, Gardner-Berry

126. AidedUnaided NAL: Dillon, Van Dun, Carter, Gardner-Berry

127. Hearing Aid Coupler Gain at 65 dB SPL Input 250 Hz500 Hz1000 Hz2000 Hz4000 Hz <0071520 * Both hearing aids are set the same. NAL: Dillon, Van Dun, Carter, Gardner-Berry

128. Auditory neuropathy NAL : Dillon, Van Dun, Carter, Gardner-Berry

129. WP ASA 2004 250 500 750 1000 1500 2000 3000 4000 6000 8000 0 10 20 30 40 50 60 70 80 90 100 110 HEARING LEVELS IN DECIBELS FREQUENCY (Hz) ABR 28/8/03 - NR ABR (CM only) ABR (CM only) NAL: Dillon, Van Dun, Carter, Gardner-Berry

130. WP ASA 2004 250 500 750 1000 1500 2000 3000 4000 6000 8000 0 10 20 30 40 50 60 70 80 90 100 110 HEARING LEVELS IN DECIBELS FREQUENCY (Hz) ABR 28/8/03 - NR CAEP 14/10/03 m g t m g t ABR (CM only) ABR (CM only) NAL: Dillon, Van Dun, Carter, Gardner-Berry

131. WP ASA 2004 250 500 750 1000 1500 2000 3000 4000 6000 8000 0 10 20 30 40 50 60 70 80 90 100 110 HEARING LEVELS IN DECIBELS FREQUENCY (Hz) ABR 28/8/03 - NR 15/3/04 - NR CAEP 14/10/03 30/3/04 ECochG 15/3/04 ECochGECochGECochGECochG m g t m g t ABR (CM only) ABR (CM only) (abnormal potentials only) NAL: Dillon, Van Dun, Carter, Gardner-Berry

132. WP ASA 2004 250 500 750 1000 1500 2000 3000 4000 6000 8000 0 10 20 30 40 50 60 70 80 90 100 110 HEARING LEVELS IN DECIBELS FREQUENCY (Hz) ABR 28/8/03 - NR 15/3/04 - NR CAEP 14/10/03 30/3/04 ECochG 15/3/04 VROA 29/4/04 m g t m g t ECochGECochGECochGECochG ABR (CM only) ABR (CM only) (abnormal potentials only) NAL: Dillon, Van Dun, Carter, Gardner-Berry

133. The HEARing CRC Member Organisations This research was financially supported by the HEARing CRC established and supported under the Australian Government’s Cooperative Research Centres Program NAL: Dillon, Van Dun, Carter, Gardner-Berry