Hearing Aid Compatibility (HAC) for Cell Phones

The FCC now requires cell phone manufacturers to test and rate their wireless handsets’ hearing aid compatibility using the American National Standards Institute (ANSI) C63.19 standard. These ratings give an indication of the likelihood a cell phone may interfere with hearing aids; the higher the rating, the less likely the cell phone-hearing aid combination will experience undesired interference. Hearing Aid Compatibility (HAC) testing involves measuring the magnetic and electric field produced by a phone to ensure it does not interfere with the sound quality of a hearing aid. The FCC defines Hearing Aid Compatibility (HAC) for cell phones in terms of two parameters; radio-frequency (RF) emissions and telecoil coupling. HAC-compliant device packages are marked with “M” or “T” ratings. The M-rating refers to the microphone mode. The T-rating refers to the telecoil mode.

M & T Ratings

  • M-Rating : Wireless devices rated M3 or M4 meet FCC requirements. M4 is the better/higher of the two ratings.
  • T-Rating : Wireless devices rated T3 or T4 meet FCC requirements and are likely to be more usable with a hearing device’s telecoil (“T Switch” or “Telephone Switch”) than unrated wireless devices. T4 is the better/higher of the two ratings.

Hearing Aid Compatibility Simulation

Hearing Aid Compatibility (HAC) sensors gather data on a 5 cm by 5 cm arbitrarily-oriented rectangle in free space. They are used to determine if a wireless device (such as a cellphone) will generate electrical and magnetic fields large enough to interfere with a hearing aid. In these cases, they are useful for evaluating the wearer’s ability to adjust the position of the phone to a better location.

hac1.jpg

  • The HAC sensor is centered at the origin of the coordinate system described in the Geometry tab.
  • This sensor collects steady-state E and H fields at grid points near the HAC plane at each frequency of interest. These values can be then interpolated onto the plane at a user-defined spatial resolution.

HAC RF Emissions Testhac2

  • 3×3 Measurement grid is defined
  • E/H-fields are measured (near field)
  • Exclusion zones are selected to eliminate hot spot regions
  • Quality categories based on signal levelshac3

Simulation Result hac4

  • Surface Resolution – This option appears whenever there is a HAC or interpolated surface sensor. It controls the resolution at which field data is shown for the sensor.
  • M-Rating – Displays the M-rating of the sensor, or the suitability of the hearing aid used with a wireless device.
  • Threshold – This is the maximum allowed field value given the current M-rating.
  • Band – Displays the band type.
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