Conny Andersson
IEC 60118-4
Conny.Andersson@edin.se
www.univox.eu
Receiver = T-coil in Hearing Instrument (HI)
No current consumption
Transmitter = Loop Amplifier and Loop
World Wide Standard
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Acoustic
Output
Input
Gain +60dB
Speech level=70dB
@1m distance
Loop Level:
Fixed @ 400mA/m
for all signals
Hearing
Instrument
M
T
switch
130dB
Coil Sensitivity
Same output level for M and T-position
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130dB
Switching between M and T will give
approximately the same output level
It could be stated differently:
0dB difference between M and T-position
Related to acoustic level: The acoustic
output is the same for T and M-position
with a 70dB acoustical input signal
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Hearing Instrument (HI)
Many parameters are fitted for the
individual. Can not be standardized
Hearing Loop system
International
Electrotechnical
Commission
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All parameters are standardized
American National Standard Institute has
many abbreviations for T-coil functions
3.4 Terms relating to measurements with inductive inputs
3.4.1 high frequency average SPL for an inductive telephone simulator (HFA-SPLITS).
The high frequency
average of the SPLITS levels (see Clause 3.4.5). The abbreviation for this term is HFASPLITS.
3.4.2 high frequency average SPL in a vertical magnetic field (HFA-SPLIV). The highfrequency
average of the SPLIV levels (see Clause 3.4.6). The abbreviation for this term is HFA-SPLIV.
3.4.3 relative simulated equivalent telephone sensitivity (RSETS). Difference in decibels
obtained
by subtracting the RTG + 60 dB SPL from the HFA-SPLITS. The abbreviation for this term is
RSETS.
3.4.4 relative test loop sensitivity (RTLS). Difference in decibels obtained by subtracting
the RTG +
60 dB SPL from the HFA-SPLIV. The abbreviation for this term is RTLS.
3.4.5 sound pressure level for an inductive telephone simulator (SPLITS). Sound
pressure level
developed in the coupler by a hearing aid with the gain control at the RTS when the input is the
magnetic field generated by a Telephone Magnetic Field Simulator (refer to Clause 3.2.5). The
abbreviation for this term is SPLITS.
3.4.6 sound pressure level in a vertical magnetic field (SPLIV). Sound pressure level
developed in
the coupler by a hearing aid with the gain control at the RTS when the input is a 31.6 mA/m
sinusoidal
alternating magnetic field parallel to the vertical reference and the input selector of the hearing
aid set
to T-position. The abbreviation for this term is SPLIV.
Good News, ANSI S3.22 committee
has decided to make T-coil
specification mandatory for quality
test inspection
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Magnetic Field Strength, 400mA/m
Coverage area/space (sitting and standing),
Should have minimum variations (+-3dB)
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Variation less
than +-3dB
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Magnetic field strength from electrical
appliances
Received directly by the T-coil
NOT by the hearing loop system
Less problematic due to stronger
regulations of electrical environment
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Hearing instrument, microphone/telecoil response
Mic
T-coil
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Hearing instrument, microphone/telecoil response
Reduced low
frequency
sensitivity
Mic
25dB
Tele-coil
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Hearing
Hearinginstrument,
intrument, microphone/telecoil response
Mic
Tele-coil
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Hearing instrument, microphone/telecoil response
Within
+-3dB
+-3dB
Mic
Tele-coil
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It is therefore impossible to judge
the full quality of a loop system by
using a Hearing Instrument
Measurements are mandatory
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The specifications for most of the
parameters for loops are for vertical
directions
This corresponds to HI
manufacturers placing the T-coil in
vertical position
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Vertical field
0dB=full level
-3dB (@45°)
Silence!
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-3dB (@45°)
Silence!
Vertical AND Horizontal Field
0dB=full level
-3dB (@45°)
full level
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-3dB (@45°)
full level
Increased low frequency response
Hum harmonics remover
Default sensitivity should follow the standard
of 400mA/m (125ms, RMS)
If the sensitivity is set higher in the Hearing
Instrument there is a strong risk for high
distortion, clipping/saturation when entering
a correct installed Loop System.
A weak loop must not be compensated by
increasing the T-coil sensitivity with a
decreased Signal to Noise ratio.
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Several channels and modulated/coded
loop system.
One “standard loop system for world
wide use in theatres etc
Other channels for school and domestic
use. Decreased Signal to Noise ratio.
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Acoustic
Output
Input
Gain +60dB
Speech level=70dB
@1m distance
Loop Level:
Fixed @ 400mA/m
for all signals
Hearing
Instrument
M
T
switch
130dB
Coil Sensitivity
Same output level for M and T-position
www.univox.eu
130dB
Acoustic
Output
Input
Long-term signals:
Speech level=70dB
@1m distance
Loop Level:
Fixed @ 100mA/m
for all signals
Gain +60dB
Hearing
Instrument
M
T
switch
130dB
Coil Sensitivity
Same output level for M and T-position
www.univox.eu
130dB
Acoustic
Output
Input
Long-term signals:
Speech level=60dB
@1m distance
Loop Level:
Fixed @ 31.6 mA/m
for all signals
Gain +60dB
Hearing
Instrument
M
T
switch
120dB
Coil Sensitivity
Same output level for M and T-position
www.univox.eu
120dB
0
