Transcript PPT - 13MB

Conny Andersson
Standards IEC 60118-4
Sound examples
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 Reverberation time = 2 sec
 Speaker @ 4m distance
 Babble noise (other speakers)
 Output from a Hearing Aid (artificial ear)
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International
Electrotechnical
Commission
American National
Standard Institute
 Harmonized world wide
 Hearing Instrument (HI)
 Hearing Loop system
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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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Level: 400mA/m
Fluctuation:
within +-3dB
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(This slide contains the notes for
the previous slide)
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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
100
200 300
500
1k
2k
3k
5k
Hz
9 seconds
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High frequency loss from 1kHz
100
200 300
500
1k
2k
3k
5k
Hz
9 seconds
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High frequency loss from 500Hz
100
200 300
500
1k
2k
3k
5k
Hz
9 seconds
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No frequency limitations
100
200 300
500
1k
2k
3k
5k
Hz
9 seconds
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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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 High background noise: -12dBA
 Tiresome
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 Low Field Strength: -12dB (100mA/m)
 Very low speech intelligibility
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 Accepted Field Strength: 0dB (400mA/m)
 Enhanced speech intelligibility
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 Accepted Field Strength: +3dB (560mA/m)
 Further enhanced speech intelligibility
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 Correct Field Strength: 0dB (400mA/m)
 Noise complies to the standard, -32dBA
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 High Field Strength: +3dB (560mA/m)
 Noise complies to -47dBA
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 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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 Follow 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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[email protected]
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