Current research at the MRC Institute of Hearing Research (Scottish Section) Co-funded by the MRC...

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 [email protected]

MRC Institute of Hearing Research (Scottish Section),

Queen Elizabeth Building,

Glasgow Royal Infirmary,

16 Alexandra Parade,

Glasgow, G31 2ER.

# 2 … MRC Institute of Hearing Research

Links

Scottish Section

MRC Institute of Hearing Research (Nottingham ; Director = David Moore)

Science & admin


Links

Chief Scientist Office,Scottish Government.

Medical Research Council.


Funding & advice

Funding & advice

Science & admin

Scottish Section


Links




NHS — GlasgowRoyalInfirmary.

GlasgowUniversity.

StrathclydeUniversity.

Funding & advice

Funding & advice

Science & admin

Staff,Students

ENT,Audiology

Science,Lecturing,

Scottish Section


Links




NHS — GlasgowRoyalInfirmary.

GlasgowUniversity.

StrathclydeUniversity.

Funding & advice

Funding & advice

Science & admin

Staff,Students

ENT,Audiology

Science,Lecturing,

Scottish Section

+ staff + patients


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?

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 1/5th of them (i.e., 1/5th of 1/4 of 1 in 5) have a hearing aid;

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 1/5th of them (i.e., 1/5th 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).

Prevalence of hearing loss


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

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

• “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;


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.





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;


High frequencies:

… head casts an acoustic shadow;

… sound at far ear is quieter than at

near ear (“ILD”)

What are the cues to direction?


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”)

Thresholds for changes in spatial angle (pure tones)


0º

10º

1000 10000

2º

4º

6º

8º

12º

Thr

esho

ld (

“Min

imum

aud

ible

ang

le”)

Frequency (Hz)

Reference direction = 30º (to right)

Reference direction = 0º (straight ahead)

Grantham (1995), after Mills (1960)

• Best ITD threshold ≈ 10 ms.

• Best ILD threshold ≈ 1 dB.

Rule of thumb for visual angles


10° ≈ the visual width of the fist held at arm’s length;

2° ≈ the visual width of the thumb .. .. ..

1.5° ≈ the visual width of the thumbnail .. .. ..

1° ≈ the visual width of the index fingernail .. .. ..

RP O’Shea (1991) “Thumb’s rule tested …” Perception 1991 (20) 415-418

Rossi and Roorda (2010) Nature Neuroscience 13:156-157

0.5 arcminutes = 1/120° = best visual acuity

Angles and people


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.xlsxNASA: Anthropometric Source Book Vol I. pIII-33


Spatial hearing, circa 1893 http://www.psychologicalscience.org/observer/getArticle.cfm?id=2454a

Spatial hearing, circa 1936


Stevens and Newman (1936)

The 24-loudspeaker ring in Glasgow


Motion tracking system (two cameras not shown)


Motion tracking to sound


Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting

responses in listeners with and without hearing impairment”, JASA

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

Illustrative trajectories


Brimijoin, McShefferty, Akeroyd (in press) “Auditory and visual orienting responses in listeners with and without hearing impairment”, JASA

BSA poster 2009

Mean fixation positions



BSA poster 2009

Velocity and latency

# 28 … MRC Institute of Hearing ResearchJASA paper fig.5

JASA paper fig. 6


Complexity of trajectory

# 29 … MRC Institute of Hearing Research BSA poster 2009


Distance perception

0

Time


Distant source in room

Distance perception


0

Time

Close source in room

0

Time

Distant source in room

Direct sound


Akeroyd, Blaschke, Gatehouse (2007). “The detection of differences in the cues to distance by elderly hearing-impaired listeners,” J. Acoust. Soc. Am. 121:1077-1089.

Direct sound + 1st reflections


Akeroyd, Blaschke, Gatehouse (2007). “The detection of differences in the cues to distance by elderly hearing-impaired listeners,” J. Acoust. Soc. Am. 121:1077-1089.

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



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 …


A noisy auditory environment Zoffany: The Academicians ofthe Royal Academy (1771)

How many sounds can one locate at once?


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 !!



Child’s voice

Task:

• 2 different adult voices from two locations;


Where is the child?

In design !!



Child’svoice

Task:

• 8 different adult voices from many locations;


Where is the child?

In design !!

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?

Speech segmentation



Never just convict them

Actual sentence

Never just conviction

Example response

Deletion beforeweak syllable

(strong syllables are underlined)

Stimuli from Cutler and Butterfield (1992)

Speech segmentation



The hunters went fulfilled

Actual sentence

The hunters went for wool

Example response

Insertion beforestrong syllable

Never just convict them

Actual sentence

Never just conviction

Example response

Deletion beforeweak syllable

(strong syllables are underlined)

Stimuli from Cutler and Butterfield (1992)

Speech segmentation



Type

Insertions before strong

Insertions before weak

Deletions before strong

Deletions before weak

MSS?

Yes

No

No

Yes

Legend

IS

IW

DS

DW

Fig. 1

Group

Young NH

Older NH

Older HI

N

16

13

12

Mean

Age

24

59

62

Mean

Hearing loss

(normal)

13 dB

33 dB

Speech segmentation



Fig. 1

Intensity Discrimination


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




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.

An illustrative hearing aid



Output (to ear)

Battery

On-offswitch

Selectorswitch

Telecoil(for induction loops)

Electronics(DSP chips)

Microphoneinputs

Microphones

“Receiver”(loudspeaker)




Output (to ear)

Battery

On-offswitch

Selectorswitch



Microphoneinputs

Microphones


Out

put l

evel

(dB

)

Input level (dB)




Output (to ear)

Battery

On-offswitch

Selectorswitch



Microphoneinputs

Microphones


Out

put l

evel

(dB

)

Linea

r:

10 d

B in →

10

dB o

ut)

Compression:

10 dB in → 3 dB out

Input level (dB)




Fig. 4

N = 37 (all aided)Mean age = 67 yearsMean hearing loss = 55 dBMean compression = x1.5

Values in bracketsare medians




Fig. 5

Error bars are 95% c.i.

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

The end


Current research at the MRC Institute of Hearing Research (Scottish Section) Co-funded by the MRC...

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