American National Standard Methods of Measurement of Compatibility between Wireless Communications Devices and Hearing Aids
|Publication Date:||14 April 2011|
This standard applies to both wireless communications devices
(WDs) and hearing aids. It sets forth uniform methods of
measurement and parametric requirements for the electromagnetic and
operational compatibility of hearing aids used with WDs, including
cellular phones, personal communications service (PCS), and
This standard is intended to apply to all types of hearing aids
with acoustic output, including, as examples, behind-the-ear (BTE),
in-the-ear (ITE), in-the-canal (ITC), and completely-in-the-ca
Users of this standard are cautioned to maintain the field strength called for in various places in the document within the limits for radio-frequency (RF) safety specified in IEEE Std C95.1TM.2
The purpose of this standard is to establish categories for hearing aids and for WDs that can 1) indicate to health care practitioners and hearing aid users which hearing aids are compatible with which WDs, 2) provide tests that can be used to assess the electromagnetic characteristics of hearing aids and WDs, and 3) assign them to these categories. The various parameters required in order to demonstrate compatibility are measured. The design of the standard is such that when a hearing aid and a WD achieve one of the categories specified, as measured by the methodology of this standard, the indicated performance is realized.
To provide for the usability of a hearing aid with a WD, several factors must be coordinated, as follows:
- The field strength emitted by a WD must not exceed the RF immunity of the hearing aid.
- The T-Coil, baseband H-field transmission of the WD must be compatible with the T-Coil mode of the hearing aid.
- The electronic noise from the WD in the T-Coil band must not degrade the reception quality to unacceptable levels.
Both the WD's RF and audio-band emissions are measured. Hence, the following measurements are made for the WDs:
a) RF near-field, E-field emissions
b) T-Coil mode, magnetic signal strength in the audio band
c) T-Coil mode, magnetic noise in the audio band
d) T-Coil mode, magnetic signal frequency response in the audio band
Corresponding to these quantities, the hearing aid is measured for the following:
- RF immunity in microphone mode
- RF immunity in T-Coil mode
The hearing aid T-Coil reception characteristics are also important when assuring the usability of the T-Coil mode. When these characteristics are coordinated, the goals of this standard are accomplished.
Two principal conditions expose hearing-aid-equipped
This standard describes preferred test methods and test facilities and, in some cases, alternative test methods and facilities. If alternative test methods or facilities are employed, every effort shall be made to establish correlation with the preferred ones. Any deviation from the preferred test methods, as set forth in this standard, shall be fully described in the test report.
Wherever the word shall is used in this standard, it indicates something mandatory. The word should indicates something that is advisory. The word may indicates an option, which is at the discretion of the test engineer.
1 The current version of this standard provides detailed procedures up to 3 GHz, although the scope has been expanded up to 6 GHz. The guidance provided goes as far as well-researched methods are available and covers the primary bands relative to this issue.
2 For information on references, see Clause 2.