Auditory Rehabilitation: State of the Art Hearing Aids and ... · Hearing Aids: Digital vs. Analog ¾90% of aids fitted in 2005 were digital ¾Describes method of signal processing

1/11/20081/11/2008 Grand Rounds OHSUGrand Rounds OHSU

Auditory Rehabilitation: State Auditory Rehabilitation: State of the Art Hearing Aids and of the Art Hearing Aids and

Other FactorsOther Factors

Gabrielle H. Saunders Ph.D.Gabrielle H. Saunders Ph.D.National Center for Rehabilitative National Center for Rehabilitative Auditory Research, Portland ORAuditory Research, Portland OR


OverviewOverviewSome statisticsSome statistics

The impaired earThe impaired ear

Causes of hearing lossCauses of hearing loss

Hearing aidsHearing aids

Approaches to rehabilitationApproaches to rehabilitation

Prevention? Prevention?


Hearing loss is a major health concern:30 million in US with hearing impairment

Prevalence increases with age: 21 million hearing-impaired in US over 45 years of age

About 30% of people over age 65 need hearing aids


Of these a HUGE percentage are veterans:

• About 414,412 veterans are service-connected for hearing loss

• Another 1.6 million have service-related hearing loss but are not receiving compensation


Army/Marine VA Major Hearing Loss Army/Marine VA Major Hearing Loss Disability Cases Disability Cases

Percent of Change Since 1986Percent of Change Since 1986

19.9

33

52.5

67.7

-13.5

-5.7

5.1

15.1

1.9 2.4 2.8 3.3 3.5 3.8 4.6 6.7 7.2 8.3 9.210.7

12.0 14.2

-12-0.03 -1.2 -2.2

-3.7 -5.2 -6.8 -7.7 -9.2 -10.7-13.6 -15.1 -15.4-14.5

-40

-20

0

20

40

60

80

87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04

Marines Army

Perc

ent c

hang

e


Study of 141,856 active duty soldiers:

Post-deployment 68% had some form of noise induced injury vs. 4% of non-deployed soldiers

• 29% had permanent threshold shift• 30% had tinnitus• 16% had significant HL• 5.6% had acoustic trauma

Helfer et al, 2005


Conductive Sensorineural

Types of hearing loss


Damage to the outer or middle ear

Effect is attenuate sound level (decrease ‘volume’)

Maximum loss is about 60dB HL

Often correctable with surgery

If not correctible, increasing the volumerestores audibility & intelligibility

Conductive loss


Damage to the hair cells

Thresholds are increased

Experience recruitment and poor frequency resolution

Raising the volume doesn’t solve problems

Much harder to correct with a hearing aid

Sensorineural loss


Differential effects of changes in threshold


u

vi

e lar

pf

o

ths

kdshchgb h

zj mn


Recruitment


120 -110 -100 -

90 -80 -70 -60 -50 -40 -30 -20 -10 -0 -

Leve

l (dB

HL)

Recruitment

Normal threshold

Impaired threshold

Normal UCL

Dynamic range of speech

Impaired UCL


Frequency resolutionFrequency resolution

Can think of the cochlear as a bank Can think of the cochlear as a bank of auditory filtersof auditory filters

These filters become broadened These filters become broadened with SNHL with SNHL


Picture of auditory filtersPicture of auditory filters

Frequency

Filte

r res

pons

e


SIG

NA

L

NOISENOISE

Filte

r res

pons

eFilter in unimpaired ear

Filter in impaired ear

1 kHz


Hearing AidsHearing Aids

Hearing aid technology has vastly Hearing aid technology has vastly improved in the last 10 years improved in the last 10 years

However, hearing aids cannot However, hearing aids cannot fully remediate hearing lossfully remediate hearing loss


Hearing aids: what are they?Hearing aids: what are they?

are basically sophisticated amplifiersare basically sophisticated amplifiers

cannot improve the signalcannot improve the signal--toto--noisenoise--ratio (yet)ratio (yet)

cannot determine what is cannot determine what is ‘‘signalsignal’’ vs. vs. what is what is ‘‘noisenoise’’

cannot restore claritycannot restore clarity


Hearing Aids: SatisfactionHearing Aids: Satisfaction

The good news The good news ((KochkinKochkin, 2005):, 2005):

0

10

20

30

40

50

60

70

80

1991 1994 1997 2000 2004

PositiveNegative

0

10

20

30

40

50

60

70

80

1991 1994 1997 2000 2004

PositiveNegative

HAs 1-4 yrs. old HAs <1 yr. old


The notThe not--suchsuch--good newsgood news

Hearing aid use

(Kochkin, 2005)

19841984 19891989 19911991 19941994 199719970%0%

10%10%

15%15%

20%20%

25%25%

5%5%

23.822.9 22.6

21.320.4

Pene

trat

ion

rate

Pene

trat

ion

rate

20002000

22.223.5

20042004


Hearing Aids: OptionsHearing Aids: OptionsStyleStyle

TechnologyTechnologySignal processing optionsSignal processing options‘‘Bells and whistlesBells and whistles’’

The future The future


BehindBehind--thethe--earear

InIn--thethe--earear

InIn--thethe--canalcanal

CompletelyCompletely--inin--thethe--canalcanal

Open canalOpen canal

Hearing Aids: StylesHearing Aids: Styles

http://www.fortworth-hearingaids.com/www.fortworth-hearingaids.com/specialoffer.html


Pros and cons of each stylePros and cons of each style

StyleStylePowerPower FeedbackFeedback Battery Battery

sizesizeEase of Ease of

insertioninsertion VisibilityVisibility

BTEBTE

ITE/ITCITE/ITC

CICCIC

Open Open canalcanal

++++++ LeastLeast LargestLargest Can be Can be hardhard 22

++++ SmallSmall EasiestEasiest 33

++ MostMost TinyTiny DifficultDifficult 11

low low gaingain SmallSmall Can be Can be

hardhard 11


Digital versus analog

Compression

Directional microphones

Noise reduction

Feedback cancellation

Hearing Aids: Signal ProcessingHearing Aids: Signal Processing


Hearing Aids: Digital vs. AnalogHearing Aids: Digital vs. Analog

90% of aids fitted in 2005 were digital90% of aids fitted in 2005 were digital

Describes method of signal Describes method of signal processingprocessing

Provides more options but is not Provides more options but is not intrinsically superior to analogintrinsically superior to analog


Addressing threshold changesAddressing threshold changes

Multiple channels that can each be Multiple channels that can each be programmed independentlyprogrammed independently

Potentially better ability to meet Potentially better ability to meet frequencyfrequency--gain target and loudness gain target and loudness growth issuesgrowth issues

In reality there is crossIn reality there is cross--over between over between channels i.e. they are not entirely channels i.e. they are not entirely independentindependent


Addressing Recruitment Addressing Recruitment

Compression: gain provided is Compression: gain provided is dependent of level of input signal. With dependent of level of input signal. With recruitment we want to shrink range of recruitment we want to shrink range of speech levels into a smaller dynamic speech levels into a smaller dynamic rangerange


120 -110 -100 -

90 -80 -70 -60 -50 -40 -30 -20 -10 -0 -

Leve

l (dB

HL)

Recruitment

Normal threshold

Impaired threshold

Normal UCL

Dynamic range of speech

Impaired UCL


CompressionCompression

Input signal level

Out

put s

igna

l lev

el


Addressing poor frequency Addressing poor frequency resolutionresolution

Need to improve the signalNeed to improve the signal--toto--noise noise (S/N) ratio(S/N) ratio

i.e. level of signal in relation to level of i.e. level of signal in relation to level of noisenoise


Hearing Aids: Hearing Aids: Directional MicrophonesDirectional Microphones

Multiple laboratory studies show HAswith directional microphones are more effective than omnidirectional microphones for listening in noise


Describes the directional sensitivity of Describes the directional sensitivity of the microphonethe microphone

Hearing aids: Hearing aids: Directional MicrophonesDirectional Microphones


Users often forget to switch settings. Adaptive directionality overcomes this

Must mark orientation on impression so Must mark orientation on impression so manufacturer can orient manufacturer can orient micsmics correctly correctly

Need to confirm directionalityNeed to confirm directionality

ConsiderationsConsiderations


Some examples of polar plots weSome examples of polar plots we’’ve measuredve measured

Banded Noise Polar Plot for HA0700258927Rhyper

707580859095

1000

1020304050

60708090100110

120130

140150160170180

190200210220230

240250260270280290300

310320330340350

Banded Noise Polar Plot for HA0700259058Rhyper

707580859095

010 20 30

4050

60708090100

110120

130140

150160170180

190200210220

230240

250260270280290300

310320

330340350

Banded Noise Polar Plot for HA0700258912Lhyper

70

80

90

1000

10 203040

5060708090100

110120

130140

150160170180

190200210220

230240

250260270280290300

310320

330340350

Banded Noise Polar Plot for Starkey 0307280277 dir

75

80

85

90

95

1000

10 2030

4050

60

70

80

90

100

110

120130

140150

160170180

190200210

220230

240

250

260

270

280

290

300310

320330

340350


Hearing aids: Noise ReductionHearing aids: Noise Reduction

People like itPeople like it

Makes sound more Makes sound more ‘‘pleasantpleasant’’

No studies have shown measurable No studies have shown measurable benefitbenefit

It has been said that “the best hearing aid is

one that will be worn….”


Hearing aids: Hearing aids: Feedback CancellationFeedback Cancellation

Feedback: Feedback: occurs when amplified occurs when amplified sound leaks out of ear canal and back sound leaks out of ear canal and back into amplifierinto amplifier

Cancellation:Cancellation: The frequency of the The frequency of the feedback signal is estimated and then feedback signal is estimated and then filteredfiltered

Generally is effective without negative consequences

Algorithms use an adaptive filter for ongoing

control


Hearing aids: Bells and WhistlesHearing aids: Bells and Whistles

Multiple programsMultiple programs

Remote controlRemote control

Volume control or notVolume control or not

TT--coilcoil Small handheld device for switching between

programs and controlling volume

Are pros and cons

Volume control used to be necessary. With

compression is now often omitted

Coil of wire which converts electromagnetic energy into electrical

energy for amplification. For phone and loop

systems

Different hearing aid settings are stored in each program User

switches programs as desired


Binaural hearing aids: wireless Binaural hearing aids: wireless betweenbetween--aid communication aid communication (Blue tooth technology)(Blue tooth technology)

Permits binaural (over bilateral) Permits binaural (over bilateral) hearing: localization, release fromhearing: localization, release frommasking, echo suppressionmasking, echo suppression

Signal processing opportunities: Signal processing opportunities: noise cancellation, beam forming noise cancellation, beam forming

Hearing aids: The FutureHearing aids: The Future


Binaural hearing aids: wireless Binaural hearing aids: wireless betweenbetween--aid and other via (Blue tooth aid and other via (Blue tooth technology)technology)

cell phone to hearing aid cell phone to hearing aid


Hearing aids: User IssuesHearing aids: User Issues

Manual dexterityManual dexterity

Cognitive statusCognitive status

ExpectationsExpectations

LifestyleLifestyle


Hearing Aids: Manual DexterityHearing Aids: Manual Dexterity

Successful HA use requires Successful HA use requires good manual dexterity good manual dexterity (insertion, manipulation, (insertion, manipulation, upkeep)upkeep)


Manual Dexterity

p<

Success using HAs r = 0.555 p< 0.01Performance with HAs r = 0.602 p< 0.001Satisfaction with HAs r = 0.802 p< 0.001

Correlations between manual dexterity and HA outcome:

Hearing Aids: Manual DexterityHearing Aids: Manual Dexterity

Kumar et al (2000)


SocialSocial

OccupationalOccupational

PsychologicalPsychological

FamilyFamily

Impacts of hearing ImpairmentImpacts of hearing Impairment

“More non-users of hearing aids reported feelings of INSECURITY, DEPRESSION and PARANOIA than users of hearing aids”

(Kochkin & Rogin 2000)

“Hearing aid users did MORE SOCIAL activities than non-users, but the SAME number

of SOLITARY activities”(Kochkin & Rogin 2000)

HI workers feel LESS COMPETENT, EMBARASSED,

WITHDRAW. Co-workers feel ANGER at the non-communicative individual.

(Hetu et al, 1988)

“Family of non-users more often said the HI relative was CONFUSED, DISORIENTED, ARROGANT & NON-CARING than did family of hearing aid users.”

(Kochkin & Rogin 2000)


Benefits reported following Benefits reported following acquisition of a hearing aid:acquisition of a hearing aid:

Hearing aid users & their relatives reported improvements in:

relationships at home

self-esteem

mental health

social, physical & emotional life


Questions to consider when Questions to consider when planning auditory rehabilitationplanning auditory rehabilitation

Is a hearing aid the best solution?

Are there co-morbid conditions?

How to assess it’s effectiveness?

What individual factors should be considered?


DualDual--Sensory ImpairmentSensory Impairment

Presence of both hearing loss and Presence of both hearing loss and vision lossvision loss

Prevalence: Prevalence:

1.7 million individuals in US 1.7 million individuals in US

21% of adults over age 70 have DSI21% of adults over age 70 have DSI

Veterans with DSI in 1995: 179,000

Veterans with DSI by 2010: 294,000

Goodrich, 1995


DualDual--Sensory Impairment: Sensory Impairment: ImpactsImpacts

DSI results in significantly more DSI results in significantly more difficulties with difficulties with ADLsADLs and and IADLsIADLs than than single impairmentssingle impairments

Are the effects additive?Are the effects additive?

Presumably 1 + 1 > 2Presumably 1 + 1 > 2


Hearing people and vision people donHearing people and vision people don’’t t communicatecommunicate

Dual Sensory Loss Consensus Dual Sensory Loss Consensus Conference in Portland 2004 revealed Conference in Portland 2004 revealed more questions than answersmore questions than answers

DualDual--Sensory Impairment: Sensory Impairment: ImpactsImpacts


DualDual--Sensory Impairment: Sensory Impairment: Clinical ConsiderationsClinical Considerations

Selection of appropriate hearing aidsSelection of appropriate hearing aids

Use of hearing aids Use of hearing aids

Provision of informationProvision of information

Functional measuresFunctional measures

Outcome measuresOutcome measures

Clinical collaborationClinical collaboration


Cognitive statusCognitive statusData shows interactions between Data shows interactions between cognitive status and ability to benefit cognitive status and ability to benefit from sophisticated signal processingfrom sophisticated signal processing

Should be considered when Should be considered when selecting hearing aid selecting hearing aid processing characteristicsprocessing characteristics



It usually takes many weeks for It usually takes many weeks for individuals to decided to acquire a HA individuals to decided to acquire a HA after learning they have hearing after learning they have hearing impairment impairment

Thus by time of fitting they have Thus by time of fitting they have distinct expectations about the distinct expectations about the HAsHAs



Expectations affect outcomeExpectations affect outcome

Could go either direction:Could go either direction:

Expectations too high Expectations too high disappointmentdisappointment

oror

Expectations too low Expectations too low selfself--fulfilling fulfilling prophecyprophecy


7

4

3

2

SAD

L sc

ore

Life-time hearing aid use

> 10 years1 to 10 years

6 weeks to 1 year

<6 weeksNever used

n=33 n=6 n=33 n=16 n=18

6

5

Personal Image

xx x

x

x

Negative Features

Positive Expectations

From Saunders & Jutai (2004)


LifestyleLifestyle

Individual needs and wants vary, thus measured outcome might not reflect patient satisfaction if we aren’t helping the patient in situations in which they want to hear.

Water aerobics anecdote!


Assistive Listening DevicesAssistive Listening Devices

Alerting devices: vibrating or flashing Alerting devices: vibrating or flashing alerting devices, clocks etc., low alerting devices, clocks etc., low frequency alarms, amplified phones, frequency alarms, amplified phones, ring enhancersring enhancers

Personal use items: personal FM systemPersonal use items: personal FM system

Hearing aid

Microphone and FM transmitter

Receiver Receiver attached via ‘audioshoe’ to BTE

hearing aid


Ecological AdjustmentsEcological Adjustmentsi.e. Improve the listening environmenti.e. Improve the listening environment

Background noiseBackground noise

Room lightingRoom lighting

Room AcousticsRoom Acoustics

• Move to a quieter place

• Look at the talker • Turn off noise, e.g. TV, dishwasher

• Use good lighting• Do not have talker sit in front of a window

Lip reading and facial expressions can increase

speech understanding by 20% even without raining

• Use soft absorbent floor and furniture coverings

• Avoid restaurants with hard floors and bare walls


Auditory Retraining TherapiesAuditory Retraining Therapies

Aim: to alter neural transmission of Aim: to alter neural transmission of sound at the cortical and subsound at the cortical and sub--cortical cortical level to improve timing and level to improve timing and synchronization of neural responses synchronization of neural responses

Relies on neural plasticity of the central Relies on neural plasticity of the central auditory systemauditory system


ComputerComputer--based, interactive programsbased, interactive programs

Require repetitive useRequire repetitive use

Tasks are usually adaptive i.e. begin Tasks are usually adaptive i.e. begin easy and get harder as performance easy and get harder as performance improvesimproves

Jury is out on effectivenessJury is out on effectiveness

Auditory Retraining TherapiesAuditory Retraining Therapies


Central system or peripheral systems Central system or peripheral systems mucked upmucked up

Holds promise for rehab in the futureHolds promise for rehab in the future


Although HL seems simple on surface Although HL seems simple on surface it is highly complexit is highly complex

Is a need for understand cause via Is a need for understand cause via appropriate appropriate evaleval. prior to rehab. . prior to rehab. beginning beginning


Technology has vastly improvedTechnology has vastly improved

Will continue to do soWill continue to do so

However, nonHowever, non--tech rehab still necessarytech rehab still necessary

When hearing loss is present and need When hearing loss is present and need rehab. a holistic approach should be rehab. a holistic approach should be usedused


Divenyi, PL; Stark, PB & Haupt, KM (2005) Decline of speech understanding and auditory thresholds in the elderly. J. Acoust. Soc. Am. 118, 1089-1100

Goodrich G (1995) Growth in a shrinking population: Visual impairment in the veteran population 1995-2010. Psychology Service and Western Blind Rehabilitation Center. VA Palo Alto Health Care System, Palo Alto, CA, pp 1-28

Helfer, TM; Jordan, NN & Lee, RB (2005). Postdeployment hearing loss in US Army soldiers seen at audiology clinics from April 1, 2005, through March 31, 2004. Am. J. Audiol. 14, 161-168

Hetu R, Riverin L, Lalande N, Getty L, St.-Cyr C (1988) Qualitative analysis of the handicap associated with occupational hearing loss. Br. J. Audiol. 22:251-264

Kochkin S (2005) MarkeTrak VII: Hearing loss population tops 31 million people. Hear. Rev. 12:16-29

Kochkin S, Rogin C (2000) Quantifying the obvious: the impact of hearing instruments on the quality of life. Hear. Rev. 7, 6-34

Kumar, M., Hickey, S., & Shaw, S. (2000). Manual dexterity and successful hearing aid use. J. Laryngol. Otol. 114, 593-597.

Lunner, T. (2003). Cognitive function in relation to hearing aid use. Int. J. Audiol. 42, S49-S58.

Saunders G, Jutai J (2004) Hearing specific and generic measures of the psychosocial impact of hearing aids. J. Am. Acad. Audiol. 15, 238-248

REFERENCES


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Documents

Auditory Rehabilitation: State of the Art Hearing Aids and ... · Hearing Aids: Digital vs. Analog ¾90% of aids fitted in 2005 were digital ¾Describes method of signal processing