October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 1Copyright 2008 US EMC Standards Corporation

HEI Study

Joe Morrissey

Motorola

ANSI ASC C63® Subcommittee 8

RadioCircuitry

Audio

Receiver

RF Source (Mobile Phone) RF Victim (Hearing Aid)

Desired Signal

RF Signal • Carrier Frequency• Burst Structure• Modulation• Dynamic Signal• Field Polarization• E- and H- components

Audio Band Noise• oscillators• clocks

Handset / Antenna • Type / Location• Radiation Pattern• Distance (Near Field)• Transmit Power

Other Noise

Receiver • Wires (Length / E-Field)• Loops (Area / H-Field)• Shielding by head

Demodulator • Square Law

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 3Copyright 2008 US EMC Standards Corporation

Hearing Aid Anatomy

Receiver

Microphone

Battery

Turnpotadjust

Molded shell

Plastic tube

On / Off / TCswitch

Telecoil

IntegratedCircuit

Wiring

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 4Copyright 2008 US EMC Standards Corporation

Captured Acoustic Products

W-CDMA

45

50

55

60

65

70

75

80

85

90

0 5 10 15 20 25 30 35 40

Net Power to Antenna, Average (dBm)

He

ari

ng

Aid

Ou

tpu

t (d

BA

)

0 5 10 15 20 25 30 35 40

Net Power to Antenna, Burst (dBm)

2100 M Hz

700 M Hz

GSM

45

50

55

60

65

70

75

80

85

90

0 5 10 15 20 25 30

Net Power to Antenna, Average (dBm)

He

ari

ng

Aid

Ou

tpu

t (d

BA

)

9 14 19 24 29 34 39

Net Power to Antenna, Burst (dBm)

2100 M Hz

700 M Hz

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 5Copyright 2008 US EMC Standards Corporation

E- vs H- Field

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 6Copyright 2008 US EMC Standards Corporation

Table B.2—Typical transmitters, output power levels, and estimated field strengths at 1 m (39 in)

Product Frequency (MHz) Power (W) Field strength @ 1 m (V/m)

Paging transmitters 49 250 110 [i] Mobile radios 138–470 25 35a Hand-held transceivers 27, 49, 138–470 5 15a Police/ambulance 138–900 10–100 22–70a Commercial BW and Public Safety (mobile)

698-806 1-2

Wireless LANs 912, 2400, 5GHz 0.1 -0.25 2.2 – 3.1 Wireless personal digital assistants 896–940 2 10 Radio modems 896–901 10 22 Cellular telephones[ii] 800–900 0.6 5.4 Personal communications satellite telephones

1610–1626.5 1 7

Licensed PCS equipment 1850–1910 1 7 BWA (3G / IMT, WiMAX mobile) 2.5 -2.689 1-2 BWA (Fixed)) 3650-3700 1-25 Public Safety 4940-4990 2 CISPR 11, CISPR 22 [iii] 25–1000 0.04 10-6 0.0014 [iv]

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 7Copyright 2008 US EMC Standards Corporation

Wi-Fi Technology

• 802.11b (2.45 GHz)• DSSS encoding format • GFSK modulation

• 802.11a (5 GHz)• OFDM encoding format• PSK,QAM modulation

• 802.11g (2.45 GHz)• DSSS / OFDM encoding format• PSK / QAM modulation

• Frame Duration• data rate• data length

• Inter-Frame Spacing• traffic• signal quality

• 802.11g• backwards compatible (b)• higher data rate (a)

Defined Parameters Dynamic Parameters

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 8Copyright 2008 US EMC Standards Corporation

GSM Bursting Structure

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 9Copyright 2008 US EMC Standards Corporation

217 Hz or 4.6 msec

October 2008 Measurement of Hearing Aid Compatibility Workshop, C63.19 (2007)

Slide 10Copyright 2008 US EMC Standards Corporation

Subjective Assessment

Technology Evaluation

Identification of a new technologyAny stakeholder can bring forward a technology for evaluation

Technological definition of technologyFactors relevant to HAC are quantified

Analytical EvaluationIs there a significant potential for HAC?

There is potential for HAC or there is not a consensus agreement on the potential for HAC.

Negligible potential for interference

-Product testing is

not required.

Experimental EvaluationDo laboratory measurements show a significant

potential for HAC?

Little or no potential for HAC

Field StudiesDo products implementing the technology show a

significant potential for HAC?

Potential for HAC still unclear?

Little or no potential for HAC

Little or no potential for HAC

Individual Product Evaluation

Potential for HAC exists.

Potential for HAC exists.

X2 X0.5

4 msec TC 550 msec T.C.

Peak DetectorRMS Level MeasurementSpectral Weighting

Similar to CISPR, ITU-R 468 Quasi-Peak DetectionSimilar to A-weighting

from square-law detector

to DC meter

The weighting function:

•The weighting function consists of straightforward spectral weighting followed by temporal weighting.

•Each step is clearly mathematically definable.

•Implementation may be in hardware or software.

20.6 Hz 12.2 kHz 107.7 Hz

737.9 Hz

369 Hz 3 kHz, 2nd orderD.F. = 0.707

x 1.2589

x 1.0864

(A-weighted)

A-Weighting Curve (after ANSI S1.4-1983 (R 2005))and Proposed Alternate Curve

-70

-60

-50

-40

-30

-20

-10

0

10

10 100 1000 10000 100000

frequency - Hz

dB

A-weight dB

Altweight dB

The spectral weighting portion:

from square-law detector(or conditionedbaseband mag-netic probe forABM2)

x2 x2

new-weighted