Cordless Telephones and Hearing Aids

1. TR41.3-05-11-003 Cordless Telephonesand Hearing Aids A Presentation on the Work of TIA TR-41.3 to the ATIS HAC Incubator Group August 23, 2005

2. Ancient History • 1982 – Telecommunications for the Disabled Act requires “essential” telephones to be usable by persons with hearing aids • 1983 – TR-41.3 creates EIA RS-504 • Axial and radial field intensity • Axial frequency response • 1984 – FCC adopts RS-504 into Part 68.316 • 1988 – Hearing Aid Compatibility Act requires virtually all wireline telephones to provide magnetic coupling

3. Recent History • 4/2004 – Informal FCC Complaints begin • Digital cordless telephones • Industry wide • 6/2004 – TIA User Premises Equipment Division (UPED) forms Hearing Aid Compatibility (HAC) Task Force • 8/2004 – TR-41.3 begins work to understand and characterize cause of digital cordless telephone interference with hearing aids • 10/2004 – UPED meets with FCC and Self Help for Hard of Hearing People (SHHH) to inform them of TIA activities

4. Recent History (cont) • 5/2005 – TR-41.3 completes preliminary work and launches SP-3-0219, Measurement Procedures and Performance Requirements for Handset Generated In-Band Magnetic Noise (to become TIA-1083) • 6/2005 – SHHH holds annual Convention in Washington, DC • Gallaudet subjective study involving 32 hearing aid users and 8 digital cordless telephones • TIA Member Companies show products intended to provide a solution

5. Gallaudet SHHH Study • 32 subjects who normally use a hearing aid when talking on the telephone • 22 women and 10 men with ages from 43 to 79 • 12 reported moderate to moderately severe hearing loss, 18 reported severe or profound hearing loss, and 2 were not sure • 27 used T-coil coupling and 5 used acoustic coupling • 8 digital cordless telephones • 5 off-the-shelf models and 3 potential solution models • 4 operating at 2.4 GHz and 4 operating at 5.8 GHz • 5 were frequency hoppers and 3 were direct sequence • 2500 set included in study for baseline reference

6. Gallaudet SHHH Study (cont) • Subjects asked to rate • Loudness (1-7, inaudible to too loud) • Percent words understood (1-5, <20% to >80%) • Interference (0-5, none to unbearable) • Usability (1-4, highly usable to not usable) • Subjects also asked to provide a yes or no answer as to whether, based on the interference they perceived, they would purchase the phone • Study funded under Grant No. H133E040013 from the National Institute on Disability and Rehabilitation Research

7. Magnetic or RF Interference?

8. Round Robin Measurements • SHHH study sets measured by 3 TR-41.3 members • Desired magnetic field axial signal level and frequency response using full band integrator as defined in draft revision of C63.19 • Undesired magnetic field axial signal level and frequency response using half band integrator as defined in draft revision of C63.19. • Compared results for following metrics: • AFI (1 kHz) – desired axial field intensity at 1 kHz • A-Weighted Noise – undesired magnetic field (half band, A wtd) • Signal Quality – AFI(1 kHz) minus A-Weighted Noise • Highest SFI – field strength of highest amplitude noise component • Magnetic SFI – A-Weighted Noise minus Highest SFI • Signal-to-Highest SFI Ratio – AFI(1 kHz) minus Highest SFI

9. T-Coil Coupling Findings • Subjective Interference rating correlates best with A-Weighted Noise and Highest SFI measures • Interference rating also shows correlation to Signal Quality and Signal-to-Highest SFI Ratio measures • Slightly lower correlation of Purchase question and Usability rating to objective measures • Poor correlation of Loudness and Percent Words ratings to any objective measures • Poor correlation of AFI (1 kHz) and Magnetic SFI to any subjective ratings

10. Current Status • Continuing to analyze Gallaudet SHHH subjective study data and objective measurements on same cordless phones by labs of 3 TR-41.3 members • Creating first draft of SP-3-0219 (to be TIA 1083) • Targeting committee ballot after 11/2005 meeting and industry ballot after 2/2006 meeting

11. SP-3-0219 Draft Direction • Addressing magnetic interference • All complaints seem to be related to T-coil use • RF power levels lower than for cell phones • Supported by SHHH study results • Relatively simple measurement procedure • Connect the probe coil normally used for Part 68 testing to a spectrum analyzer instead of a narrow-band tracking analyzer • Borrow the half-band integrator and A-weighting concepts from revision of C63.19 (Draft 3.1, October 7, 2004) • Set performance criteria to obtain high percentage of “Not Annoying” and “Highly Usable” ratings.

12. Further Information • Documentation available on TR-41.3 FTP site: ftp.tiaonline.org/tr-41/tr41.3/Public • Publicly available (anonymous FTP) • Arranged in folders organized by meeting date • Alternative browser access (no password required) • Next TR-41 meeting is week of November 7-11, 2005 in Santa Fe, NM • TR-41.3 will meet on Thursday afternoon • Anyone may attend one meeting as a guest • Additional information available on TR-41 web page: www.tiaonline.org/standards/sfg/tr-41

13. Contacts • TR-41.3 Chair is James Bress of AST Technologies (jrbress@asttechlabs.com) • SP-3-0219 Document Editor is Al Baum of Uniden (abaum@uniden.com) • TR-41 Chair is Stephen R Whitesell of VTech (swhitesell@vtech.ca) • SHHH study Research Audiologist is Linda Kozma-Spytek of Gallaudet University’s Technology Access Program (linda.kozma-spytek@gallaudet.edu)