1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2013 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AS4950BAEROSPACESTANDARDAS4950 REV. BIssued 1998-03 Revised 2007-03 Reaffirmed 201
5、3-07 Superseding AS4950A (R) Design and Performance Criteria Transport Aircraft Portable Megaphones RATIONALE AS4950B has been reaffirmed to comply with the SAE five-year review policy. 1. SCOPE This SAE Aerospace Standard (AS) provides design criteria and performance tests for portable, handheld, b
6、attery-powered, electronic megaphones used by aircraft crew members to provide information and guidance in the event of an aircraft emergency or other non-routine situation. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein.
7、 The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in
8、 this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 RTCA Publications Available from Radio Technical Commission for Aeronautics Inc., 1828 L Street, NW, Suite 805, Washington, DC 20036, Tel: 202-833-9339, www.rtca.org. RTCA/DO-160D
9、 Environmental Conditions and Test Procedures for Airborne Equipment Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2.2 Related Publications The following publications are provided for informational
10、 purposes only and are not a required part of this document. 2.2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. ARP577 Emergency Placarding - Internal and Ex
11、ternal ARP583 Flight Attendant Stations ARP997 Passenger Cabin Emergency Equipment Stowage 2.2.2 FAA Publications Available from Federal Aviation Administration, 800 Independence Avenue, SW, Washington, DC 20591, Tel: 866-835-5322, www.faa.gov. Code of Federal Regulations, Title 14, Part 21, Certifi
12、cation Procedures for Products and Parts Code of Federal Regulations, Title 14, Part 25, Airworthiness Standards: Transport Category Airplanes Code of Federal Regulations, Title 14, Part 121, Operating Requirements: Domestic, Flag, and Supplemental Operations AC 121-6 Portable Battery-Powered Megaph
13、ones TSO-C137 Aircraft Portable Megaphones 2.3 Definitions 2.3.1 RATED INPUT Rated input shall be determined as follows: The megaphone shall be set up under free field conditions and an input applied to the microphone from an acoustically isolated artificial voice, emitting a warble frequency of 125
14、0 to 1750 Hz at a pressure of 10,000,000 micropascals at 0.75 in (1.91 cm) and placed at a distance of 0.06 in (0.15 cm) away from and on the microphone axis. The electrical output of the microphone measured across a resistance equal to the input impedance shall be considered rated input. 2.3.2 FULL
15、 GAIN The full gain is defined as the input/output ratio of the electronic amplifier at rated input that produces maximum megaphone output within the distortion limits allowed. 2.3.3 USABLE GAIN The usable gain is defined as the input/output ratio of the electronic amplifier at rated input with the
16、megaphone volume control (if provided) set as high as possible without feedback. SAE INTERNATIONAL AS4950B Page 2 of 7_ Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2.4 Mandating and Recommending
17、Words “Shall” - The word “shall” indicates a mandatory criterion. “Should” - The word “should” indicates a criterion for which an alternative, including noncompliance, may be applied if it is documented and justified. 3. GENERAL REQUIREMENTS 3.1 Handle Size The grip shape shall allow easy and secure
18、 handling of the megaphone with either hand. The grip circumference shall be no more than 6.5 in (16.5 cm) and the grip length shall be no less than 3.5 in (8.9 cm). 3.2 Weight The megaphone shall weigh no more than 6 lb (2.7 kg) including batteries. 3.3 Balance The megaphone shall be balanced to al
19、low easy one-handed operation for 1 hour of continuous use. 3.4 Durability and Reliability The megaphone shall be designed to meet the following requirements: 3.4.1 All materials used except small parts (knobs, triggers, fasteners, seals, and small electrical parts) that would not contribute signifi
20、cantly to the propagation of a fire shall be self-extinguishing when tested in accordance with applicable requirements of 14 CFR 25.853. 3.4.2 The megaphone should comply with Section 5 of this standard. 3.4.3 The megaphone shall be shown to operate continuously at usable gain for a period of at lea
21、st 4 hours after being completely submerged in seawater for a period of 2 seconds. 3.5 Stowage Provisions The megaphone design may include a stowage bracket. If included, the stowage bracket shall meet the following specifications: 3.5.1 The bracket shall be designed to minimize the possibility of i
22、nadvertent actuation. 3.5.2 The bracket shall allow the release and removal of the megaphone using only one hand. 3.5.3 The bracket should allow for ease of serviceability checks. 3.5.4 The bracket shall be of a contrasting color to the color of the megaphone. 3.6 Color The majority of the megaphone
23、s exterior surface shall be of a bright color (e.g., white, yellow, orange) known to be highly visible in such circumstances as near darkness, smoke, and/or immersion in water. SAE INTERNATIONAL AS4950B Page 3 of 7_ Copyright SAE International Provided by IHS under license with SAENot for ResaleNo r
24、eproduction or networking permitted without license from IHS-,-,-3.7 Anti-feedback Design The megaphone design and construction materials shall minimize the possibility of feedback when operated in a transport category aircraft cabin. 3.8 Power Source The megaphone power source shall be self-contain
25、ed with no external electrical connections. An external indicator of power source status is desirable. The manufacturer shall provide a defined power service life for the power source or a means of indicating or testing the status of the power source. 3.9 Activation The means for activating the mega
26、phone shall be obvious, and if incorporated into the handle, shall be invoked by positive compression of the handle itself, or a trigger or button mechanism actuated by the index finger of the holding hand. 3.10 Volume Adjustment If included, volume adjustment hardware shall comply with the followin
27、g: 3.10.1 The volume adjustment shall be controlled by a knob that facilitates easy operation. 3.10.2 Volume controls shall increase the volume when turned clockwise and decrease the volume when turned counterclockwise. 3.10.3 The volume adjustment shall provide logarithmic control of the megaphone
28、output for a linear rotation of the knob. 3.11 Maintainability The megaphone should be easily maintained with common tools. 3.12 Markings The megaphone shall be marked with the specification to which it has been qualified. 4. MINIMUM PERFORMANCE CRITERIA 4.1 Operational Life At the end of the define
29、d power source service life, the megaphone shall be capable of continuously producing rated output sound pressure at rated input for a period of not less than 1 hour. 4.2 Rated Output Pressure With the rated input applied to the electronic amplifier set to provide full gain, the megaphone output pre
30、ssure shall be measured at a distance of 10 ft (3.0 m) on the horn axis. The rated output pressure shall be 112 dBA minimum (referenced to 13.79 psi (95,079 pascals). 4.3 Usable Output Pressure With the megaphone set up under free field conditions and an input applied to the microphone from an acous
31、tically isolated artificial voice emitting a warble frequency of 1250 to 1750 Hz at a pressure of 10,000,000 micropascals at 0.75 in (1.91 cm) placed at a distance of 0.06 in (0.15 cm) away from and on the microphone axis and the electronic amplifier set to the usable gain position, the megaphone ou
32、tput pressure shall be measured at a distance of 10 ft (3.0 m) on the horn axis. The usable output pressure shall be 112 dBA (referenced to 13.79 psi (95,079 pascals). SAE INTERNATIONAL AS4950B Page 4 of 7_ Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproducti
33、on or networking permitted without license from IHS-,-,-4.4 Amplifier Distortion With rated input applied to the electronic amplifier set to provide full gain, the distortion contained in the amplifier output (measured across any resistive load within 20% of rated load) shall not exceed 10% at the u
34、sable output pressure, nor shall it exceed 15% at the rated output pressure at any frequency between 400 and 5500 Hz. With rated input applied to the electronic amplifier set to provide a megaphone output pressure equal to usable output pressure, the distortion contained in the amplifier output (mea
35、sured across any resistive load within 20% of rated load) shall not exceed 10%, nor shall it exceed 15% at the rated output pressure at any frequency between 400 and 5500 Hz. 4.5 Output Sound Pressure Distribution With rated input applied to the electronic amplifier set to provide a megaphone output
36、 pressure equal to the rated output pressure, sound pressure measurements shall be made at both 15 (0.26 rad) and 30 (0.52 rad) off the megaphone sound axis. Four measurements shall be made at each off axis angle, one in the horizontal plane on each side of the sound axis and one in the vertical pla
37、ne above and below the sound axis. The off axis output pressure for each off-axis angle shall be figured as the arithmetical average of the four readings. The maximum off-axis deviation from the rated output pressure shall be 3 dBA at 15 and 6 dBA at 30. 4.6 Frequency Response The megaphone shall be
38、 set up under free field conditions with an input applied to the microphone from an acoustically isolated artificial voice emitting a warble frequency of 1250 to 1750 Hz at a sound pressure of 14,100,000 micropascals at 0.75 in (1.91 cm) placed at a distance of 0.06 in (0.15 cm) away from and on the
39、 microphone axis. The megaphone output shall be measured at a distance of 10 ft (3.0 m) on the horn axis, and the megaphone volume control shall be set to provide a measured output pressure of 106 dBA (referenced to 13.79 psi (20 micropascals). The input frequency shall then be varied over a range o
40、f 400 to 5500 Hz and the megaphone output pressure measured. The megaphone output pressure shall vary no more than 10 dBA. The volume control shall then be set to yield an output of 99 dBA (referenced to 13.79 psi (20 micropascals) and the input frequency again varied over a frequency range of 400 t
41、o 5500 Hz. The measured megaphone output pressure shall vary no more than 10 dBA through this range. 4.7 Internal Noise With the electronic amplifier input bridged with a resistor equal in value to the input impedance and the amplifier output terminated with a resistance equal to the megaphone load
42、impedance, set the amplifier to provide full gain. The measured voltage across the output load shall be 55 dBA below rated output pressure level when measured with a thermal type of voltmeter. 4.8 Loudspeaker Noise With the megaphone operating at usable output pressure, the natural resonance(s) of t
43、he mechanical structure(s) shall occur at frequencies outside the usable frequency range of the loudspeaker. In addition, other inherent megaphone noises shall not impair the output sound quality. 4.9 Operation in Aircraft Environment The directional characteristics of the microphone unit while it i
44、s mounted on the horn assembly shall be measured: Use a pink noise source with an acoustical frequency response that is flat within 3 dBA over the usable bandwidth of the megaphone. Pink noise source shall be at a distance of 10 ft (3.0 m) from the megaphone in an anechoic chamber. Rotate the megaph
45、one system and record the polar sensitivity of the microphone output voltage by monitoring the output of the megaphone speaker amplifier terminated into a resistive load equivalent to the average impedance of the horn loudspeaker. The microphone must have 10 dBA less signal at the most rearward poin
46、t of rotation (180 degrees) when compared to the on axis (0 degree) signal. SAE INTERNATIONAL AS4950B Page 5 of 7_ Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-5. TEST PROCEDURES - ENVIRONMENTAL 5
47、.1 Temperature Variation The megaphone shall comply with the test requirements specified in RTCA DO-160D, Section 5, Category C, as it applies to Section 4, Category AI and 4.5.1, 4.5.2, and 4.5.3. 5.2 Humidity The megaphone shall comply with the test requirements specified in RTCA DO-160D, Section 6, Category A. 5.3 Operational Shock The megaphone shall comply with the test requirements specified in RTCA DO-160D, Section 7, Paragraph 7.2. 5.4 Waterproofness The megaphone shall comply with the test requi
