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Hearing Loop System. Conny Andersson Standards IEC 60118-4 Sound examples. [email protected]. Hearing Instrument. Reverberation time = 2 sec Speaker @ 4m distance Babble noise (other speakers) Output from a Hearing Aid (artificial ear). International Standards, IEC. - PowerPoint PPT Presentation
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Hearing Loop System
Conny Andersson
Standards IEC 60118-4Sound examples
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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 seconds100 200 300 500 1k 2k 3k 5k Hz
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High frequency loss from 1kHz
9 seconds100 200 300 500 1k 2k 3k 5k Hz
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High frequency loss from 500Hz
9 seconds100 200 300 500 1k 2k 3k 5k Hz
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No frequency limitations
9 seconds100 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.
