SC-226 MEETING MINUTES Working Group JANUARY 14 ... - RTCA

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RTCA Paper No. 021-13/SC226-010 February 6, 2013 Another question was raised concerning whether the graph in the Bose paper takes into account the female voice. Bose will look into this. Bose offered to write some proposed language for the standard based on their paper. The other manufacturers participating agreed with the information proposed. The committee welcomed Bose’ paper. Boeing and Airbus both agreed that with new language based on the paper by Bose, they will be able to select amongst varying manufacturer’s ANR headsets and have a consistent way to make a comparison between them, and thereby more easily certify the headsets for their aircraft without significant testing as was needed in the past. Bose also suggested that instead of using power as the input to test the headset, voltage should be used as active headsets no longer have the same impedance as passive headsets. Input power is less important when an active circuit is connected in between the input and the speaker. A consistent input voltage is deemed to have more value for both passive and active applications. Bose will also get with Sennheiser and Bosch to discuss all aspects of their paper to come to consensus prior to returning to the next meeting with their recommended language. They will also address how to insure that ANR headset meet the same DO-160 audio performance requirements from DO-214 section 2.5 as are required by other microphones. Participants responsible for headsets (ANR and passive) work are: Anthony Mangiameli – Bose Dan Gauger, Bose Steven Parker – Bosch Jorg Buchberger – Sennheiser Christian Grone – Sennheiser Christian Kast – Holmco Fifth item of discussion: EASA Deviations EASA deviation paper ETSO.DevP.52d.pdf (Deviations requests #52 for an ETSO approval for CS-ETSO applicable to Headsets, Speakers and Aircraft Microphones (ETSO-C57a, C58a) Consultation Paper) should also be addressed as part of the headset working group’s efforts on how to best measure sensitivity. Current language in the standard is as follows: 2.3.3.1 Headsets and Handsets When tested in accordance with the test procedure of subparagraph 2.7.2.1a, each ear phone shall have a sensitivity of 90 ±5 dB SPL (re: 20 uPa) with an input power level of 1 mW (RMS). A volume control may be provided to Page 4 of 20
RTCA Paper No. 021-13/SC226-010 February 6, 2013 meet this requirement. below 75 dB SPL. However, it shall not be possible to reduce the level Language in the EASA deviation paper is as follows: To allow better harmonisation with the used side tone adjustments industry has received demands from operators to increase the output sound pressure to values above 95 dB (re: 20 µPa) when providing 1 mW (RMS) to the headset or handset. Today technology allows providing higher sound pressure levels out of 1 mW (RMS) without producing distortions…….. ETSO-C57a#7 – Headsets and Speakers Deviate from RTCA DO-214 2.3.3.1 and provide a higher Sound Pressure Level (SPL) of 90 -5/+18 dB instead of 90 +/- 5 dB SPL (re: 20 µPa) out of 1 mW (RMS) input signal…… Action has been given to the headset working group to complete by April 2013. Proposal based on EASA deviation paper is to study changing the headphone sensitivity tolerance from +/- 5dB to +8/-5dB. The working group will study and bring back their recommendation to the group. 6 th item of discussion: Oxygen mask mic performance testing requirements, Murzeau Frank – Lem Elno and Rosier, Julie – Lem Elno Discussion around characterizing the performance of oxygen mask microphones while installed in the oxygen mask. The oxygen mask microphone can be understood to include the mask assembly, the microphone installed inside the mask assembly, and any circuitry that is included between the output of the microphone and the audio system. The mask, microphone and circuitry can be called the oxygen mask microphone system. Rosier offered a presentation addressing performance of oxygen mask microphones compared to DO- 214. Currently oxygen mask microphones are characterized according to the hand mic test requirements of DO-214, without the microphone installed in the oxygen mask, and using the same couplers and equipment. The problem experienced by audio system designers and installers is that the output of the oxygen mask mic is often mismatched with other microphones that feed the same system so resistor padding must be applied in the installation to bring the oxygen mask microphone output level down to the same level as the other microphones. An artificial head was shown by Bose which, theoretically, could be used to test the oxygen mic when it is installed in the mask. But there does not exist any performance data on how the microphone performed when installed in the mask and therefore, the committee does not yet know how to performance requirements for the oxygen mask and oxygen mask mic when integrated together. Page 5 of 20
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SC-226 MEETING MINUTES Working Group JANUARY 14 ... - RTCA

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