What is Hearing Aid Compatibility (HAC) testing?
Hearing aid users often complain that they often hear a "clicking" noise from their hearing aids when someone nearby is making a phone call, which indicates that the mobile phone and hearing aid may be incompatible. Based on this situation, in September 2006, the FCC of the United States enforced the HAC (Hearing Aid Compatibility) certification program for mobile phone manufacturers. The HAC reference standard is ANSI C63.19 (American National Standard Method for Compatibility Measurement of Wireless Communication Equipment and Hearing Aids). According to the standard definition, consumers can judge the compatibility of a certain model of hearing aids with mobile phones by comparing the anti-interference level of the hearing aids and the corresponding mobile phone signal emission level.
Introduction to Hearing Aid Compatibility Test
Hearing aid users often complain that they hear a "clicking" noise from their hearing aids when someone nearby is making a phone call, which indicates that the mobile phone and hearing aid may be incompatible. Based on this situation, in September 2006, the FCC of the United States enforced the HAC (Hearing Aid Compatibility) certification program for mobile phone manufacturers. Its HAC reference standard is ANSI C63.19 (National Standard Method for Compatibility Measurement of Wireless Communication Equipment and Hearing Aids in the United States). According to the standard definition, consumers can judge the compatibility of a certain model of hearing aid with a mobile phone by measuring the anti-interference level of the hearing aid and the corresponding mobile phone signal emission level.
The HAC test plan requires that the limit value of the tested mobile phone be within M3 (the test results are divided into M1~M4). The specific definition of the limit value will be explained in detail later. In addition to HAC, T-coil (audio test) must also require the limit value to be within the range of T3 (the test results are divided into T1~T4).
The HAC test system of BTF Lab can complete the RF test and acoustic band electromagnetic signal index requirements according to the HAC standard. The test scope includes wireless communication devices (WD) and hearing aids (HA). The test frequency is between 800~950MHz and 1.6~2GHz. Cordless phones, mobile phones, personal communication services (PCS), etc. at this frequency can all be HAC certified.
Simple test process for electric and magnetic fields (near-field radiation test process for wireless communication equipment): Make sure the probe and test instrument are working properly.
2. Initialize the field strength probe to scan the area
3. Determine the exclusion area, set isolation and rescan other areas, and record the maximum reading electric field and magnetic field to complete the scan
4. Confirm and record the classification
5. Rescan the electric field and magnetic field if necessary
The main measuring instruments used are
1. Near-field electric field probe;
2. Near-field magnetic field probe;
3. Bullet positioning device;
4. The support system of wireless communication devices (WD);
5. Auxiliary equipment such as RF shielding room;
In the near-field test, the near-field probe uses the electric field probe or magnetic field probe to scan the maximum field strength of the measurement area in the area of 5cm*5cm. In multiple pulse cycles, the average field strength of the object under test can be obtained by measuring the peak value and calculating the average value of the measurement and the known duty cycle of the wireless communication device. The closest point distance between the probe and the reference plane of the wireless communication device must be 1.0cm. Before the wireless communication device is tested for near-field radiation, the following steps must be performed: 1. Calibrate the peak readings of the electric field and magnetic field probes in the modulation mode of the wireless communication device; 2. Check and confirm the repeatability and accuracy of the probe positioning system; 3. Confirm that the reflected interference of the object under test is more than 20dB lower than the expected signal, which can be achieved by repeatedly measuring the same wireless communication device in multiple positions and directions. The reading difference caused by reflection must not be greater than ±0.8dB; after confirming that the probe and test instrument are working normally and the wireless communication device is in the transmitting mode, the field strength probe can be initialized and the area scan can be performed. At the same time, the system will automatically record the maximum reading (V/m or A/m), and the results will be classified according to the table below.
HAC (hearing aid compatibility) wireless communication equipment electric field and magnetic field testing are briefly introduced. This issue will briefly introduce the requirements for the magnetic field strength measurement (T-coil) of wireless equipment in the audio band in the HAC test.
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HAC testing is based on the standard ANSI-C63-19, and the national standard is YD/T 1643-2007. In the measurement of the magnetic field strength of wireless communication equipment in the audio band, we need to test and evaluate three values. The first value is the magnetic field density of the intentional signal (system signal) at the centre frequency of the audio band, the second value is the frequency response of the intentional signal in the entire audio band, and the third value is the difference between the magnetic field strength of the intentional signal (system signal) and the unintentional signal (interference signal).
T-Coi test and measurement instruments include the following equipment
1. Base station simulator/RF communication tester supporting audio input or output
2. Probe coil assembly
3. True RMS voltmeter
4. 1/3 octave bandpass filter
5. Power supply
6. Helmholtz calibration coil
The HAC detection method is: controls the wireless communication device to be in call mode and require the base station simulator to provide simulated audio signals to the wireless communication device. The base station simulator controls the wireless communication device to be in the maximum transmission power state. This is mainly to take into account the impact that its baseband part may have on the coil in the earpiece when it is accurately counted in the maximum power mode. It should be noted that the measurement needs to be linked with RF lines instead of wireless methods, which is mainly to shield the impact of RF transmission signals on the measurement results during the measurement process. The entire test process is completed by the following multi-level procedures. First, the magnetic field strength of the audio frequency band useful for the hearing aid T-coil is measured. The second step is to measure the magnetic field component of the unintentional signal to determine the impact of the intentional signal on the audio frequency band from the wireless communication device display and battery current path. The following is the general measurement process (wireless communication device audio engineer WeChat test process):
1. Determine the calibration of the measuring instrument
2. Set up and verify the test configuration to determine the reference value
Measure the intentional audio band signal
Measure the unintentional audio band signal
1. Signal quality
2. Magnetic field strength
3. Frequency response
Determine and record classification information
The purpose of HAC certification is to prevent the electromagnetic field formed around the antenna of digital mobile phones during communication from affecting the hearing aids used by disabled people. Our HAC testing laboratory is the only laboratory in China that provides third-party HAC testing and certification. It fully meets the testing requirements of the American standard ANSI-C63-19 and the national standard YD/T 1643-2007 and has completed a large number of HAC tests and pre-research work for domestic mobile phone companies, ensuring that their communication products meet the protection requirements of various countries for disabled people.