A.1Axes definition for hearing aid RF immunity tests
The Z axis is the vertical axis, the X axis is approximately parallel to the side surface of the user’s head and orthogonal to the Z axis, and the Y axis is orthogonal to both the Z and X axes. Alternately, the Y axis may be defined by a line through the center points of the ears on the head. The +Z direction is up, the +Y direction is into the head, for a right-hand side hearing aid position, and the +X direction is from the back of the head to the front of the head.
The hearing aid reference orientation is defined by the manufacturer for each type of hearing aid with respect to this framework to represent the typical orientation on the user, similar to the example shown in Figure A.1 for the BTE hearing aid.
Figure A.1—BTE hearing aid
A.2WD RF emission measurements reference and plane
Figure A.2 through Figure A.4 illustrate the references and reference plane that shall be used in the WD emissions measurement.
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The grid is 50.0 mm by 50.0 mm area that is divided into nine evenly sized blocks or sub-grids.
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The grid is centered on the audio frequency output transducer of the WD (speaker or T-Coil).
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The grid is in a reference plane, which is defined as the planar area that contains the highest point in the area of the phone that normally rests against the user’s ear. It is parallel to the centerline of the receiver area of the phone and is defined by the points of the receiver-end of the WD handset, which, in normal handset use, rest against the ear.
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The measurement plane is parallel to, and 10.0 mm in front of, the reference plane.
Figure A.2—WD reference and plane for RF emission measurements
A.2.1Gauge blocks for setting measurement distance to probe
Figure A.3—Gauge block with E-field probe
Figure A.4—Gauge block with H-field probe
NOTE—For reference purposes the grid used for Clause 4 testing of the WD in T-Coil mode has been added to this graphic.
Figure A.5—Axis and planes for WD audio frequency magnetic field measurements
Figure A.5 illustrates the three standard probe orientations. Position 1 is the axial orientation of the probe coil; orientation 2 and orientation 3 are radial orientations. The space between the measurement positions is not fixed. It is recommended that a scan of the WD be done for each probe coil orientation and that the maximum level recorded be used as the reading for that orientation of the probe coil.
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The reference plane is the planar area that contains the highest point in the area of the phone that normally rests against the user’s ear. It is parallel to the centerline of the receiver area of the phone and is defined by the points of the receiver-end of the WD handset, which, in normal handset use, rest against the ear.
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The measurement plane is parallel to, and 10 mm in front of, the reference plane.
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The reference axis is normal to the reference plane and passes through the center of the receiver speaker section (or the center of the hole array); or may be centered on a secondary inductive source. The actual location of the measurement point shall be noted in the test report as the measurement reference point.
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The measurement points may be located where the axial and radial field intensity measurements are optimum with regard to the requirements. However, the measurement points should be near the acoustic output of the WD and shall be located in the same half of the phone as the WD receiver. In a WD handset with a centered receiver and a circularly symmetrical magnetic field, the measurement axis and the reference axis would coincide.
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The relative spacing of each measurement orientation is not fixed. The axial and two radial orientations should be chosen to select the optimal position.
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The measurement point for the axial position is located 10 mm from the reference plane on the measurement axis. The actual location of the measurement point shall be noted in test reports and designated as the measurement reference point.
Annex B
(normative)
Test frequencies B.1Acoustic test frequencies
Table B.1 lists the test frequencies and 1/3 octave test bandwidths to be used for the test contained in this standard. These frequencies are from ISO 3-1973 and ISO 266-1975.
Table B.1—Acoustic test frequencies
1/3 octave band
(Hz)
|
Included frequencies
(Hz)
|
50
|
44.7 to 56.2
|
63
|
56.2 to 70.8
|
80
|
70.8 to 89.1
|
100
|
89.1 to 112.0
|
125
|
112 to 141
|
160
|
141 to 178
|
200
|
179 to 224
|
250
|
224 to 282
|
315
|
282 to 355
|
400
|
355 to 447
|
500
|
447 to 562
|
630
|
562 to 708
|
800
|
708 to 891
|
1000
|
891 to 1120
|
1250
|
1120 to 1410
|
1600
|
1410 to 1780
|
2000
|
1780 to 2240
|
2500
|
2240 to 2820
|
3150
|
2820 to 3550
|
4000
|
3550 to 4470
|
5000
|
4470 to 5620
|
NOTE—The required measurement points for WD testing use frequencies from 300 Hz to 3000 Hz. See 7.3.
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