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Introduction on HAC Hearing Aids Release Time:2021-12-22

HAC is short for Hearing Aid Compatibility which test electromagnetic compatibility of mobile phones and hearing aids. It is divided into two parts RF and T-coil. It also defines two levels of immunity- compatible with neighbors and compatible with users. Mobile phones and hearing aids will interfere with each other when operation. Therefore, the Federal Communications Commission (FCC) specifies to do testing on compatibility of mobile phones and hearing aids. Both of two hearing aid modes, microphone mode and telecoil mode need to be tested. FCC sets T1-T4, M1-M4 level to calculate the risk of interference.

The American National Standards Institute (ANSI) adopts ANSI C63.19 standard. According to the regulations of the Federal Communications Commission (FCC), mobile phones of all manufacturers must comply with HAC compatibility (M3-4 and T3-4).


HAC test:

The HAC test is divided into two parts:

1. RF part: RF-E radio frequency electric field, RF-H radio frequency magnetic field. It uses E-field and H-field miniature probes to test the electric and magnetic fields in the near field emitted by the mobile phone. When digital mobile phone moves close to hearing aid, the digital pulse from digital mobile phone antenna will be obtained by hearing aid’s microphone and inductive coil, which cause the hearing aid user hear "Ziz" noise and affect its own function.

2. T-coil part: Magnetic field of ABM1 audio signal and magnetic field of ABM2 audio noise. The test uses a T-coil probe to test the magnetic field emitted by the mobile phone. When the digital mobile phone moves close to hearing aid, it causes feedback from the hearing aid. For an all-digital hearing aid, as long as it has a sufficiently powerful feedback cancellation function, this acoustic interference can be eliminated.


Hearing aids sold to the United States must be tested in compliance with HAC standards as shown in the table below:


Test Items

FCC Test Standard

Measurement Methods

FCC 47 CFR§20.19;

ANSI C63.19-2011

Reference KDB files.

Test Level Requirements

RF: M3-M4 (It includes M1-M4)


The low, middle and high channel of each   frequency

Frequency Band (MHz)

It is as same as frequency supported by   phones

Note: HAC testing is only required for FCC   while it is not required by other countries in the current.


FCC has compulsorily requires to assess HAC part. AGC test equipment covers the highest requirement of HAC test standard. Also, AGC is capable of testing up to 6GHz and complete RF test, SAR test, HAC testing and certificate application with the combination of SAR equipment. AGC aims to provide a better and efficient one-stop service.


Question collection:


Why it needs test HAC? What does HAC mean?

HAC is the abbreviation of Hearing Aid Compatibility, which intends to evaluate the electromagnetic compatibility of hearing aids and mobile phones. When a person who wearing hearing aid use a mobile phone or get a close to mobile phone user,  he may come across a lot of trouble if the mobile phone and the hearing aid cannot achieve electromagnetic compatibility. He may not be able to hear, or he may hear very annoying "Ziz" sound. The FCC divides the above two situations into user compatibility and neighbor compatibility.

How to determine HAC test result is pass or fail?

The HAC test project is divided into two parts: RF part and T-coil part

RF judgment level: M1-M4. FCC accepted level is M3&M4, means it is PASS. M4 has the highest performance.

T-coil judgment level: T1-T4. FCC accepted level is T3%T4, means it is PASS; T4 has the highest performance.

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