v Telecommunications Industry AssociationTR41.N.n-YY-MM-XXX

TEST PLAN GOAL: To determine the ranges of user-preferred telecoil magnetic signal levels and S/N ratios, according to the measurement specifications and criteria laid out in ANSI C Some additional information will be gained on hearing aid telecoil orientations. Test Plan 1 S. Julstrom (Etymotic Research) L. Kozma-Spytek (RERC Telecom Access) S. Isabelle (Motorola)

Participants Participation criteria: must be adults, must be daily hearing aid users, must use the telephone (rather than TTY or Relay) regularly for most of their calls, and must primarily use the telecoil mode of their hearing aids for telephone calls. Participant characteristics (n=12): Age range: years old (8F, 4M) Hearing loss: 1 mild-moderate, 1 moderately severe, 7 severe, 2 profound, and 1 didn’t know Hearing aid use: >10 yrs. Age of hearing aids: <6 yrs. Hearing aid style: 11 BTEs, 1 ITE Hearing aid type: 5 digital, 2 programmable, 5 analog Voice telephone use: 10 daily, 2 several times a week Speech over the Telephone: 3 Almost Completely Intelligible, 7 Mostly Intelligible, 2 Somewhat Intelligible Typical coupling mode: 10 t-coil, 2 w/o HA (Note: The RF immunity of the hearing aids is not important for these tests since WDs or RF links are not used.)

Instrumentation and Test Set Up

Full-band speech at typical conversational level (~65 dB-SPL), with 200 Hz - 5 kHz pink noise recording at ITU-T P.56-measured level for level setting. Vocoded speech at adjustable magnetic levels, with 1 kHz tone recording at the reference level for level measuring. At center of circular coil: H(A/m) = N*I(A)/D(m) Broadband noises at adjustable magnetic levels, with 1 kHz tone recording at their A-weighted, T- coil response levels for level measuring. ACOUSTIC REFERENCE MAGNETIC SPEECH SOURCE MAGNETIC NOISE SOURCE Signal Sources Test Stimuli

Speech Sources AMR MR12.2 codec EVRC codec VSELP codec AMBE++ codec Noise Sources 100 Hz, 20% DC (Training) GSM (J-STD-007) UMTS (T1/T1P1/3GPP) Display CDMA (TIA/EIA/IS 2000) TDMA (TIA/EIA-136) iDEN Note: Time intermittency effects of the interference were not considered. All noise types were presented as continuous interfering signals.

PerpendicularTransverseLongitudinal Measuring Telecoil Orientation Choosing the Source Orientation

Procedure for the Magnetic Matching Level Tests Measure Telecoil Orientation. Select best orientation magnetic hat: Perpendicular Transverse Longitudinal Subject adjusts hearing aid volume control for normal use in microphone mode with loudspeaker acoustic speech reference. Apply magnetically coupled speech to hearing aid in telecoil mode at -25 dBA/m (nominal match to 65 dB-SPL). Subject adjusts the magnetic level to subjectively match the 65 dB-SPL acoustic level.

Procedure for the Magnetic Speech Level Tests Subject adjusts the magnetic speech level to their preferred, most comfortable listening level. Subject then adjusts the magnetic speech level to their lowest acceptable level and highest acceptable level, with the order of these level adjustments counterbalanced across subjects. Tester resets the magnetic level to the subject's previous MCL and reconfirms setting by having subject rate the speech on a loudness scale.

Instructions for the Magnetic Speech Level Tests Most Comfortable Speech Level – your preferred, most comfortable listening level for an extended telephone call. Minimum Acceptable Speech Level – the quietest setting you would consider usable for an extended telephone call. Maximum Acceptable Speech Level – the loudest setting you would readily tolerate for an extended telephone call.

Axial & Radial

Procedure for Magnetic S/N Tests Tester uses adaptive procedure to find subject’s magnetic noise level threshold in the presence of the speech. Select randomized noise source with corresponding speech source at MCL (1 of 6). With speech at their self-selected MCL, the subject adjusts the magnetic noise level to: their highest usable level, their highest normal use level, their highest level for excellent performance. The level adjustments are accomplished in the order given above or reversed with order counterbalanced across noise sources and subjects. Once each magnetic noise level adjustment is complete, subjects rate the speech in noise on an annoyance scale and a usability scale. Provide training for magnetic S/N tests.

Instructions for Magnetic S/N Tests Excellent Performance - You would find a phone with this level of noise to be highly usable. You would have no complaints about this amount of noise for extended phone calls. Acceptable for Normal Use – You would find this level of noise to be acceptable for normal, regular use of a phone. You would accept this amount of noise for an extended phone call without becoming tense or tired. Usable for a Brief Call - With this level of noise you could successfully complete a brief phone call. However, you would not accept this amount of noise for normal, regular phone use.

25 15

Lower Category Boundary needed to include: Usable Normal UseExcellent Performance 70% of the observations 20 dB S/N27 dB S/N34 dB S/N (30 dB S/Nθ) * 80% of the observations 23 dB S/N29 dB S/N37 dB S/N (34 dB S/Nθ) * 90% of the observations 27 dB S/N34 dB S/N42 dB S/N (37 dB S/Nθ) * *Note: The effective limit for the excellent performance category is the threshold of audibility for the noise in the presence of the intended speech signal at the subject’s most comfortable listening level. (n=71/performance category) Minimum S/N Ratios