IEEE C63.19-2011 pdf download American National Standard Methods of Measurement of Compatibility between Wireless Communications Devices and Hearing Aids
.3 Organization and use of the standard
These technical requirements specify the measurement methods and categorical levels to ensure hearing aidoperational compatibility with WDs.
To ensure hearing aid and WD compatibility, it is essential that uniform measurement methods be specified for hearing aid RF immunity and WD RF emissions. In addition, in order to provide for T-Coil mode, the WD T-Coil signal must be evaluated for the signal strength, intended/unintended signal ratio,and frequency response of the signal in the audio band.
Ihere are several factors impacting hearing aid performance when used in the presence of a WD. Thehearing aid can be exposed to near-field illumination (when the hearing aid user uses a WD) or to far-fieldillumination (when the radiating element is at a distance from the hearing aid user). Different styles of hearing aids (for example, BTE,ITE, ITC, and CIC) are positioned differently with respect to the WD WDs can operate at different frequencies and utilize different transmission schemes.
Hearing aids can operate in an acoustic coupling mode or a T-Coil coupling mode. In acoustic modehearing aids use a microphone to pick up acoustic sound waves generated by the WD. In T-Coil mode, the microphone output is disabled (or attenuated) and a base band H-field signal, generated by the WDbecomes the signal source. During T-Coil operation, the baseband H-field generated by the WD is intendedto be the primary coupling mechanism to the hearing aid. The WD also can produce unintended H-fields(the result of circulating currents). Such H-fields produce noise, if detected during T-Coil operation, or canintroduce interference in hearing aid circuits, even in the acoustic mode.
The WD generates an electromagnetic field as the main communication means with the public telephonenetwork. However, it is possible for this field to interfere with the hearing aid’s proper operation.Interference is produced as a result of pickup and demodulation within the hearing aid circuitry. The goals are to control the E-field distribution and to provide hearing aids with a minimum amount of electromagnetic immunity such that levels in direct proximity to the hearing aid (with WD in normal position) are manageable and do not interfere with basic hearing aid functionality.
The technical requirements have been organized into ten general clauses. The following list is a summaryof each clause:
Clause I, Overview: Describes the scope and purpose of the standard Clause 2, Normative references. References used in this standard.Clause 3, Definitions,acronyms, and abbreviations: Definitions, acronyms, and abbreviations used in this standard.Clause 4, Low-power exemption: Evaluates the need for RF testing under Clause 5. Some low.power RF modes can be exempted from mandatory testing.
Clause 5, Wireless device RF emissions test: Prescribes the measurements of the RF field strength in the near field generated by a WD in the region controlled for use by a hearing aid.