sound field testing

Modernising Children’s Hearing Aid Services

Sound Field TestingSound Field Testing

MCHAS TEAMMCHAS TEAM

Wave 4 SFR 17/05/04


What can aided sound field thresholds tell What can aided sound field thresholds tell us?us?


Aided ThresholdsAided Thresholds10

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LimitationsLimitations

Relies on valid Relies on valid behavioural behavioural responseresponse



Limited frequency resolutionLimited frequency resolution

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No information on real ear output characteristics No information on real ear output characteristics HAHA



Poor test-retest Poor test-retest reliabilityreliability

Need at least 15 dB Need at least 15 dB difference between difference between conditions before conditions before significant effect significant effect (Hawkins 1985)(Hawkins 1985)..

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Provide little indication of speech audibility, Provide little indication of speech audibility, especially when using WDRC.especially when using WDRC.

Seewald 2003


Limitations Limitations

Inaccurate in regions of normal hearingInaccurate in regions of normal hearing

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So………… what information is provided?So………… what information is provided?

An indication of the An indication of the child’s/infant’s auditory child’s/infant’s auditory performanceperformance

Good visual/auditory Good visual/auditory demonstration to parents demonstration to parents between ‘no hearing aids’ between ‘no hearing aids’ vs ‘hearing aids’.vs ‘hearing aids’.


A word of cautionA word of caution

Be aware of possible interactions with Be aware of possible interactions with hearing aid features.hearing aid features.Number of channelsCompression speedNoise algorithmsActive feedback control


What the Aided Threshold is and is notWhat the Aided Threshold is and is not

IS:IS: -index to reflect softest perceptible sound w/o vc-index to reflect softest perceptible sound w/o vc-Functional gain reflects gain for -Functional gain reflects gain for softest sound softest sound

(not (not conversational level)conversational level) IS NOT:IS NOT:

-Reflect gain for any input level other than soft-Reflect gain for any input level other than soft-Reflect gain for conversational sounds-Reflect gain for conversational sounds-Reflect loudness comfort-Reflect loudness comfort-Reflect processing of DSP aids eg. NR etc-Reflect processing of DSP aids eg. NR etc

Kuk, FKuk, F(AAA 2004)(AAA 2004)


What Real-Ear Measure is and is notWhat Real-Ear Measure is and is not

IS:-Allows determination of physical output of IS:-Allows determination of physical output of hearing aid at different input levels:hearing aid at different input levels: **Gain for Gain for conversational, soft and loud soundsconversational, soft and loud sounds

**Effect of signal processing eg.compression, NR Effect of signal processing eg.compression, NR etcetc

IS NOT:-A perceptual response ie. Does not tell IS NOT:-A perceptual response ie. Does not tell how soft a child can hearhow soft a child can hear

-cannot predict aided threshold-cannot predict aided thresholdKuk, FKuk, F

(AAA 2004)(AAA 2004)


So, should we be using both for a fuller So, should we be using both for a fuller picture?picture?

PerhapsPerhaps If so, what should be the optimal aided If so, what should be the optimal aided

threshold?threshold? Depends on criteria:Depends on criteria:

**Importance of hearing soft or low level inputImportance of hearing soft or low level input

sounds and meaningfulness of thesesounds and meaningfulness of these*Degree of hearing loss and possible dead*Degree of hearing loss and possible dead

regionsregions*Limitations of hearing aid (as discussed) *Limitations of hearing aid (as discussed)


THANK-YOU!THANK-YOU!

sound field testing

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