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Current research at the MRC Institute of Hearing Research (Scottish Section) Co-funded by the MRC and by the Chief Scientist Office of the Scottish Government.

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Presentation on theme: "Current research at the MRC Institute of Hearing Research (Scottish Section) Co-funded by the MRC and by the Chief Scientist Office of the Scottish Government."— Presentation transcript:

1 Current research at the MRC Institute of Hearing Research (Scottish Section) Co-funded by the MRC and by the Chief Scientist Office of the Scottish Government Health Directorates. Michael A. Akeroyd MRC Institute of Hearing Research (Scottish Section), Queen Elizabeth Building, Glasgow Royal Infirmary, 16 Alexandra Parade, Glasgow, G31 2ER.

2 # 2 … MRC Institute of Hearing Research Links Scottish Section MRC Institute of Hearing Research (Nottingham ; Director = David Moore) Science & admin

3 # 3 … MRC Institute of Hearing Research Links Chief Scientist Office, Scottish Government. Medical Research Council. MRC Institute of Hearing Research (Nottingham ; Director = David Moore) Funding & advice Science & admin Scottish Section

4 # 4 … MRC Institute of Hearing Research Links Chief Scientist Office, Scottish Government. Medical Research Council. MRC Institute of Hearing Research (Nottingham ; Director = David Moore) NHS — Glasgow Royal Infirmary. Glasgow University. Strathclyde University. Funding & advice Science & admin Staff, Students ENT, Audiology Science, Lecturing, Scottish Section

5 # 5 … MRC Institute of Hearing Research Links Chief Scientist Office, Scottish Government. Medical Research Council. MRC Institute of Hearing Research (Nottingham ; Director = David Moore) NHS — Glasgow Royal Infirmary. Glasgow University. Strathclyde University. Funding & advice Science & admin Staff, Students ENT, Audiology Science, Lecturing, Scottish Section + staff + patients

6 # 6 … MRC Institute of Hearing Research Overview We do fundamental and translational research on: what does a hearing loss mean for someone? how does it affect how they listen? what does it mean for their quality of life? what benefits do hearing aids offer? who benefits from hearing aids?

7 Prevalence # 7 … MRC Institute of Hearing Research Davis et al (2007) HTA Report; Executive Summary For the population: About 1 in 5 adults has a bilateral hearing problem that affects their hearing and communication … in Scotland that’s about 750,000 people; About 1/4 of them would benefit from a hearing aid; About 1/5 th of them (i.e., 1/5 th of 1/4 of 1 in 5) have a hearing aid;

8 Prevalence # 8 … MRC Institute of Hearing Research Davis et al (2007) HTA Report; Executive Summary For the population: About 1 in 5 adults has a bilateral hearing problem that affects their hearing and communication … in Scotland that’s about 750,000 people; About 1/4 of them would benefit from a hearing aid; About 1/5 th of them (i.e., 1/5 th of 1/4 of 1 in 5) have a hearing aid; For the NHS: Around 1.5 – 2 million appointments per year (≈ 0.5 million patient journeys); £120 million per year; 700,000 hearing-aids fitted per year; Some 250,000 waiting for first-appointment or re-assessment (in 2006).

9 Prevalence of hearing loss # 9 … MRC Institute of Hearing Research Those who said “yes” to “Do you have any difficulty with your hearing?” in a postal questionnaire (N = 31793) : By age-group 14 – 34 years 35 – 54 years 55 – 75 years Older than 75 Everyone 7% 17% 32% 46% 19% By occupation (55-75 years only) Manual Non-manual 43% 29% By gender (55-75 years only) Male Female 41% 23% Davis et al (2007) HTA Report

10 What does a hearing loss mean? Difficulties in communication & social function Talking to family or friends or colleagues; Conversations on telephone; Listening anywhere noisy (e.g. restaurants, bars) Difficulties in hearing & listening Travel announcements at airports or on trains; Dialogue at cinema, theatre, radio; Distance, direction, and motion of sounds; Segregation and identification of sounds; Effort involved in listening. Difficulties in society reduced education and skills; reduced employment opportunities.

11 Impairment, disability, handicap “Auditory impairment” = what goes wrong e.g. increase in absolute thresholds, wider auditory filters; “Auditory disability” = consequences for auditory situations e.g. poorer ability to identify speech in noisy backgrounds; “Auditory handicap” = consequences for general life e.g. avoidance of noisy situations;

12 # 12 … MRC Institute of Hearing Research You have two microphones (the ears) about 20 cm apart, with the gap filled by something solid and roughly spherical (the head). (Almost) all you need know about spatial hearing

13 # 13 … MRC Institute of Hearing Research You have two microphones (the ears) about 20 cm apart, with the gap filled by something solid and roughly spherical (the head). (Almost) all you need know about spatial hearing Your auditory system can work out Timing differences across the ears; Level differences across the ears; And it can concentrate on just the start of a sound, ignoring the rest.

14 # 14 … MRC Institute of Hearing Research You have two microphones (the ears) about 20 cm apart, with the gap filled by something solid and roughly spherical (the head). (Almost) all you need know about spatial hearing Your auditory system can work out Timing differences across the ears; Level differences across the ears; And it can concentrate on just the start of a sound, ignoring the rest. So having two ears means You can determine where a sound source is; Improve its detectability; Do better in complex auditory situations like rooms;

15 # 15 … MRC Institute of Hearing Research High frequencies: … head casts an acoustic shadow; … sound at far ear is quieter than at near ear (“ILD”) What are the cues to direction?

16 # 16 … MRC Institute of Hearing Research High frequencies: … head casts an acoustic shadow; … sound at far ear is quieter than at near ear (“ILD”) What are the cues to direction? Low frequencies: … tiny acoustic shadow (due to diffraction); … sound at far ear is about same as at near ear; … but it takes longer to get there (“ITD”)

17 Thresholds for changes in spatial angle (pure tones) # 17 … MRC Institute of Hearing Research 0º 10º º 4º 6º 8º 12º Threshold (“Minimum audible angle”) Frequency (Hz) Reference direction = 30º (to right) Reference direction = 0º (straight ahead) Grantham (1995), after Mills (1960) Best ITD threshold ≈ 10  s. Best ILD threshold ≈ 1 dB.

18 Rule of thumb for visual angles # 18 … MRC Institute of Hearing Research 10° ≈ the visual width of the fist held at arm’s length; 2° ≈ the visual width of the thumb ° ≈ the visual width of the thumbnail ° ≈ the visual width of the index fingernail RP O’Shea (1991) “Thumb’s rule tested …” Perception 1991 (20) Rossi and Roorda (2010) Nature Neuroscience 13: arcminutes = 1/120° = best visual acuity

19 Angles and people # 19 … MRC Institute of Hearing Research 10° ≈ the visual width of a person about 3-m distant; 2° ≈ the visual width of a person about 15-m distant; 1.5° ≈ the visual width of a person about 20-m distant; 1° ≈ the visual width of a person about 30-m distant (Width of person (over shoulders) ≈ 50 cm) subtendedangles1_28march2010.xlsx NASA: Anthropometric Source Book Vol I. pIII-33

20 # 20 … MRC Institute of Hearing Research Spatial hearing, circa 1893

21 Spatial hearing, circa 1936 # 21 … MRC Institute of Hearing Research Stevens and Newman (1936)

22 The 24-loudspeaker ring in Glasgow # 22 … MRC Institute of Hearing Research

23 Motion tracking system (two cameras not shown) # 23 … MRC Institute of Hearing Research

24 Motion tracking to sound # 24 … MRC Institute of Hearing Research Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA

25 Motion tracking to sound # 25 … MRC Institute of Hearing Research Press pageup twice to reset Task: A random* speaker plays a sentence; Turn your head to it; * Not entirely random … actually a very carefully controlled sequence that has every possible speaker and speaker-to-speaker jump in it; Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA

26 Illustrative trajectories # 26 … MRC Institute of Hearing Research Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA BSA poster 2009

27 Mean fixation positions # 27 … MRC Institute of Hearing Research Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA BSA poster 2009

28 Velocity and latency # 28 … MRC Institute of Hearing Research JASA paper fig.5 JASA paper fig. 6 Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA

29 Complexity of trajectory # 29 … MRC Institute of Hearing Research BSA poster 2009 Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA

30 Distance perception 0 Time # 30 … MRC Institute of Hearing Research Distant source in room

31 Distance perception # 31 … MRC Institute of Hearing Research 0 Time Close source in room 0 Time Distant source in room

32 Direct sound # 32 … MRC Institute of Hearing Research Akeroyd, Blaschke, Gatehouse (2007). “The detection of differences in the cues to distance by elderly hearing-impaired listeners,” J. Acoust. Soc. Am. 121:

33 Direct sound + 1st reflections # 33 … MRC Institute of Hearing Research Akeroyd, Blaschke, Gatehouse (2007). “The detection of differences in the cues to distance by elderly hearing-impaired listeners,” J. Acoust. Soc. Am. 121:

34 Direct sound + 1st + 2nd reflections Full system uses 75 sounds: listener perceives a sound at the same distance as the real sound in the real room # 34 … MRC Institute of Hearing Research

35 # 35 … MRC Institute of Hearing Research The auditory world is complicated … … there is never just one sound coming from one direction* * unless you are in an anechoic room, etc. The auditory world changes too … … sounds start, stop, move, & vary … … people fidgit, move, walk … But …

36 # 36 … MRC Institute of Hearing Research A noisy auditory environment Zoffany: The Academicians of the Royal Academy (1771)

37 How many sounds can one locate at once? # 37 … MRC Institute of Hearing Research Adult’s voice Child’s voice Task: 1 adult voice from one location; 1 child voice from a random location; Where is the child? In design !!

38 How many sounds can one locate at once? # 38 … MRC Institute of Hearing Research Child’s voice Task: 2 different adult voices from two locations; 1 child voice from a random location; Where is the child? In design !!

39 How many sounds can one locate at once? # 39 … MRC Institute of Hearing Research Child’s voice Task: 8 different adult voices from many locations; 1 child voice from a random location; Where is the child? In design !!

40 Speech segmentation # 40 … MRC Institute of Hearing Research from Kuhl, 2004, Nature Reviews Neuroscience Thereare nos ilen ces bet weenword s Segmented by the actual gaps in the signal: There are no silences between words Segmented by the your speech & language systems: Woodfield & Akeroyd (submitted) “The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults” … but how well does speech segmentation work in hearing impaired adults?

41 Speech segmentation # 41 … MRC Institute of Hearing Research Woodfield & Akeroyd (submitted) “The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults” Never just convict them Actual sentence Never just conviction Example response Deletion before weak syllable (strong syllables are underlined) Stimuli from Cutler and Butterfield (1992)

42 Speech segmentation # 42 … MRC Institute of Hearing Research Woodfield & Akeroyd (submitted) “The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults” The hunters went fulfilled Actual sentence The hunters went for wool Example response Insertion before strong syllable Never just convict them Actual sentence Never just conviction Example response Deletion before weak syllable (strong syllables are underlined) Stimuli from Cutler and Butterfield (1992)

43 Speech segmentation # 43 … MRC Institute of Hearing Research Woodfield & Akeroyd (submitted) “The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults” Type Insertions before strong Insertions before weak Deletions before strong Deletions before weak MSS? Yes No Yes Legend IS IW DS DW Fig. 1 Group Young NH Older NH Older HI N Mean Age Mean Hearing loss (normal) 13 dB 33 dB

44 Speech segmentation # 44 … MRC Institute of Hearing Research Woodfield & Akeroyd (submitted) “The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults” Fig. 1

45 Intensity Discrimination # 45 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Fig. 1 Play a reference sound (“standard interval”) then play a slightly-more intense copy (“test interval”) or Play a slightly-more intense copy then the reference sound

46 Intensity Discrimination # 46 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Fig. 1 Play a reference sound (“standard interval”) then play a slightly-more intense copy (“test interval”) or Play a slightly-more intense copy then the reference sound Adaptively vary the amount of the increment depending how the person responds to “which one is louder?” Continue until “threshold” for level difference is found.

47 An illustrative hearing aid # 47 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Output (to ear) Battery On-off switch Selector switch Telecoil (for induction loops) Electronics (DSP chips) Microphone inputs Microphones “Receiver” (loudspeaker)

48 An illustrative hearing aid # 48 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Output (to ear) Battery On-off switch Selector switch Telecoil (for induction loops) Electronics (DSP chips) Microphone inputs Microphones “Receiver” (loudspeaker) Output level (dB) Input level (dB)

49 An illustrative hearing aid # 49 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Output (to ear) Battery On-off switch Selector switch Telecoil (for induction loops) Electronics (DSP chips) Microphone inputs Microphones “Receiver” (loudspeaker) Output level (dB) Linear: 10 dB in → 10 dB out) Compression: 10 dB in → 3 dB out Input level (dB)

50 Intensity Discrimination # 50 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Fig. 4 N = 37 (all aided) Mean age = 67 years Mean hearing loss = 55 dB Mean compression = x1.5 Values in brackets are medians

51 Intensity Discrimination # 51 … MRC Institute of Hearing Research Whitmer & Akeroyd (submitted) “Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification” Fig. 5 Error bars are 95% c.i.

52 Summary: What does a hearing loss mean? Difficulties in communication & social function Talking to family or friends or colleagues; Conversations on telephone; Listening anywhere noisy (e.g. restaurants, bars) Difficulties in hearing & listening Travel announcements at airports or on trains; Dialogue at cinema, theatre, radio; Distance, direction, and motion of sounds; Segregation and identification of sounds; Effort involved in listening. Difficulties in society reduced education and skills; reduced employment opportunities. + impairment, disability, handicap

53 The end # 53 … MRC Institute of Hearing Research


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