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Hearing Loop System

Conny Andersson

Standards IEC 60118-4

Sound examples

Conny.Andersson@edin.se

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Hearing InstrumentReverberation time = 2 secSpeaker @ 4m distanceBabble noise (other speakers)Output from a Hearing Aid (artificial ear)

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International Standards, IEC

Harmonized world wide

Hearing Instrument (HI)

Hearing Loop system

InternationalElectrotechnicalCommission

American NationalStandard Institute

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IEC 60118-4, “Loop Standard”

Magnetic Field Strength = 400mA/m.

Relates directly to the output level of the Hearing Instrument

Coverage area/space (sitting and standing), +-3dB

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Field distribution – level/coverage

Level: 400mA/m

Fluctuation: within +-3dB

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Field distribution – level/coverage

(This slide contains the notes for the previous slide)

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Frequency response

High frequency damping or metal loss is increased as a function of the distance to the loop wire. It cannot be fully compensated by the loop amplifier.

It can be compensated by the loop figuration.

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No frequency limitations

9 seconds

100 200 300 500 1k 2k 3k 5k Hz

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High frequency loss from 1kHz

9 seconds

100 200 300 500 1k 2k 3k 5k Hz

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High frequency loss from 500Hz

9 seconds

100 200 300 500 1k 2k 3k 5k Hz

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No frequency limitations

9 seconds

100 200 300 500 1k 2k 3k 5k Hz

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Surrounding noise (hum)

Background noise (hum) from electrical appliances creates noise directly into the Hearing Instrument

Standard: less than -32dBA (-47dBA)

Level, Magnetic Field Strength 400mA/m

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Background Noise (hum)High background noise: -12dBATiresome

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Adding a weak amplifier Low Field Strength: -12dB (100mA/m)Very low speech intelligibility

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Stronger amplifier – same noiseAccepted Field Strength: 0dB (400mA/m)Enhanced speech intelligibility

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Approved field strength– same noiseAccepted Field Strength: +3dB (560mA/m)Further enhanced speech intelligibility

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Complies to standardCorrect Field Strength: 0dB (400mA/m)Noise complies to the standard, -32dBA

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High quality Loop SystemHigh Field Strength: +3dB (560mA/m)Noise complies to -47dBA

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Conclusions of sound examples

Systems that sounds “noisy” is often a reflection of a weak hearing loop amplifier.

Loop systems could often easily be updated to comply with the level requirements (with increased Signal to Noise ratio and speech intelligibility).

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Conclusion and adviseFollow the international standard

Do not trust the manufacturers coverage area as they are highly overstated for practical installations. Trust real measurements.

A hearing instrument cannot be used to certify a hearing loop system.

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Thank you for your attention!

Conny.Andersson@edin.se