SAE AIR 1826A-2016 Acoustical Considerations for Aircraft Environmental Control System Design.pdf

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 theref

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3、cation 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: +1 724-776-4970 (out

4、side USA)Fax: 724-776-0790Email: CustomerServicesae.orgSAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/AIR1826AAEROSPACEINFORMATION REPORTAIR1826 REV. AIssued 1989-07Reaffirmed 2011-01Revised 2016

5、-08Superseding AIR1826Acoustical Considerations for AircraftEnvironmental Control System DesignRATIONALEThe report required revision to reflect current technology of aircraft ECS noise sources and reduction methods.FOREWORDNoise levels in aircraft passenger cabins and flight stations have primarily

6、been caused, in the past, by the engines and the external airflow. The introduction of high by-pass ratio engines of considerably lower noise level, plus improved treatments for aerodynamic noise have resulted in significantly quieter interiors. Against these lower background levels, however, the no

7、ise from the environmental control system (ECS) is likely to be more noticeable and may be the dominant contributor to the overall interior noise level. It is important, therefore, for the designer to appreciate the principles governing the generation of ECS noise and to understand the available mea

8、ns for controlling and reducing this noise.TABLE OF CONTENTS1. SCOPE 41.1 Purpose. 42. REFERENCES 42.1 Applicable Documents 42.1.1 SAE Publications. 42.1.2 ANSI Publications . 42.1.3 ASTM Publications 42.1.4 Code of Federal Regulations (CFR) . 52.1.5 European Aviation Regulations. 52.1.6 U.S. Govern

9、ment Publications 52.1.7 Applicable References 52.2 Related Publications . 53. FUNDAMENTALS OF ACOUSTICS. 53.1 Sound 53.2 Noise . 63.3 Frequency Spectrum. 63.4 Octave Bands 73.5 Levels and Decibels 83.6 Decibel Calculations 103.7 Comparative Levels of Common Sounds . 12SAE INTERNATIONAL AIR1826A Pag

10、e 2 of 444. DESIGN APPROACH . 124.1 Design Verification 135. NOISE SUPPRESSION METHODS. 135.1 Location and Orientation. 135.2 Absorptive Materials 145.2.1 Solid Foams 155.2.2 Fibers 155.2.3 Selection Criteria. 155.3 Transmission Loss 175.4 Mufflers 185.4.1 Absorptive Muffler Design. 205.5 Vibration

11、Isolation 225.6 Damping 245.7 Wrappings . 275.8 Enclosures 275.9 Active Noise Control 276. APPLICATION OF NOISE SUPPRESSION METHODS 296.1 Cooling Units. 296.1.1 Air Cycle Machine . 296.1.2 Vapor Cycle Machines 306.1.3 Ram Air Inlets 306.2 Bleed Air High Pressure Pneumatic Equipment . 306.2.1 Air Tur

12、bine Motor 306.2.2 Emergency Power Units 306.2.3 Control Valves. 316.2.4 Bleed Air Discharges. 316.2.5 Jet Pumps . 316.3 Air Distribution Systems 336.3.1 Ducting 336.3.2 Plenums 356.3.3 Outlets. 356.3.4 Grilles 366.3.5 Gaspers. 386.4 Air Exhaust Systems. 386.4.1 Flow Regulating Valves. 386.5 Fans 42

13、6.5.1 General 426.5.2 Vapor Cycle System Fans. 436.5.3 Ground Cooling Fans 447. NOTES 447.1 Revision Indicator 44FIGURE 1 WAVELENGTH IN AIR VERSUS FREQUENCY AT 68 F (20 C) 6FIGURE 2 EXAMPLE SOUND SPECTRUM 7FIGURE 3 SOUND PRESSURE AND PRESSURE LEVEL RATIOS 9FIGURE 4 CHART FOR COMBINING LEVELS. 11FIGU

14、RE 5 TYPICAL FOUR-ENGINE COMMERCIAL JET TRANSPORT MEASURED NOISE LEVELS 14FIGURE 6 UNFACED URETHANE FOAM 0.5 INCH (0.0127 M) THICK DENSITY 3.8 LB/FT3M3 (60.7 KG/) . 17FIGURE 7 THEORETICAL TL OF MASS-CONTROLLED LIMP PANELS 19FIGURE 8 TYPICAL DUCT LINING . 21FIGURE 9 EXAMPLES OF NOISE CONTROL METHODS.

15、 23FIGURE 10 TYPICAL NOISE CONTROL RESULTS. 23FIGURE 12 VARIATION OF MODULUS WITH TEMPERATURE FOR A TYPICAL VISCOELASTIC MATERIAL 26FIGURE 13 ANCS, FEEDFORWARD CONTROL APPROACH 28FIGURE 14 ANCS, FEEDBACK CONTROL APPROACH. 29FIGURE 15 GENERALIZED SCHEMATIC OF JET PUMP AND NOISE ABSORPTIVE LINING . 32

16、SAE INTERNATIONAL AIR1826A Page 3 of 44FIGURE 16 COMPARISON OF NOISE DOWNSTREAM OF A JET PUMP USED TO PULL AIR FROM LAVATORIES AND GALLEYS . 33FIGURE 17 OUTLET NOISE TEST 34FIGURE 18 DUCT BRANCHING 34FIGURE 19 DUCT ROUTING. 35FIGURE 20 DUCT NETWORKING 35FIGURE 21 PLENUM CONFIGURATION 36FIGURE 22 CRE

17、W AIR OUTLETS. 37FIGURE 23 GRILLE NOISE LEVEL - EFFECT OF VELOCITY. 39FIGURE 24 VARIATION OF GRILLE NOISE WITH AREA AT CONSTANT VOLUME FLOW . 40FIGURE 25 GASPER OPERATION AFFECTING CABIN NOISE . 41FIGURE 26 A TYPICAL BUTTERFLY OUTFLOW CONTROL VALVE, CROSS SECTION . 42TABLE 1 OCTAVE PASS BANDS . 8TAB

18、LE 2 COMPARATIVE LEVELS OF COMMON SOUNDS. 12TABLE 3 SOUND ABSORPTIVE MATERIAL PROPERTY COMPARISON . 16TABLE 4 MAXIMUM ACHIEVABLE ENCLOSURE NOISE REDUCTION. 27TABLE 5 SPECIFIC POWER LEVEL FOR VANE-AXIAL FANS . 43SAE INTERNATIONAL AIR1826A Page 4 of 441. SCOPEThis Aerospace Information Report (AIR) is

19、 limited in scope to the general consideration of environmental control system noise and its effect on occupant comfort. Additional information on the control of environmental control system noise may be found in 2.3 and in the documents referenced throughout the text.This document does not contain

20、sufficient direction and detail to accomplish effective and complete acoustic designs.1.1 PurposeThe purpose of this AIR is to provide aid for the reduction of environmental control system noise levels and to minimize theireffect on passengers and crew members through engineering design. The reader

21、should be aware that the material included in this document is for general guidance purposes only.2. REFERENCES2.1 Applicable DocumentsThe following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of oth

22、er 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 this document, however, supersedes applicable laws and regulations unless a s

23、pecific exemption has been obtained.2.1.1 SAE PublicationsAvailable from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.orgAIR1168/3 Aerothermodynamic Systems Engineering and DesignARP1307 Meas

24、urement of Exterior Noise Produced by Aircraft Auxiliary Power Units (APUs) and Associated Aircraft Systems During Ground OperationARP1323 Type Measurements of Airplane Interior Sound Pressure Levels During CruiseARP4245 Quantities for Description of the Acoustical Environment of the Interior of Air

25、craftARP4721/1 Monitoring Aircraft Noise and Operations in the Vicinity of Airports: System Description, Acquisition, and Operation2.1.2 ANSI PublicationsCopies of these documents are available online at http:/webstore.ansi.org.ANSI S1.6-1984 (R 2006) Preferred Frequencies, Frequency Levels, and Ban

26、d Numbers for Acoustical Measurements2.1.3 ASTM PublicationsAvailable from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org.ASTM C522-03 Standard Test Method for Airflow Resistance of Acoustical MaterialsASTM E90-09 Standard

27、Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and ElementsSAE INTERNATIONAL AIR1826A Page 5 of 442.1.4 Code of Federal Regulations (CFR)Available from the United States Government Printing Office, 732 North Capitol Street, NW, Washington, DC 20401, Tel:

28、 202-512-1800, www.gpo.gov.14 CFR Part 25 Airworthiness Standards: Transport Category Airplanes2.1.5 European Aviation RegulationsAvailable from European Aviation Safety Agency, Postfach 10 12 53, D-50452 Cologne, Germany, Tel: +49-221-8999-000, www.easa.eu.int.CS-25 Certification Specifications for

29、 Large Aeroplanes2.1.6 U.S. Government PublicationsCopies of these documents are available online at http:/quicksearch.dla.mil.MIL-STD-740-2 Structureborne Vibratory Acceleration Measurements and Acceptance Criteria of Shipboard EquipmentMIL-STD-1472 Human Engineering Design Criteria for Military Sy

30、stems, Equipment and FacilitiesMIL-STD-1474 Noise Limits2.1.7 Applicable ReferencesJ. S. Lamancusa, Engineering Noise Control, Pennsylvania State University, 20002.2 Related PublicationsThis list of publications is provided for informational purposes only. These publications are not a required part

31、of this SAE Aerospace Technical Report.L. L. Beranek, Noise and Vibration Control, Institute of Noise Control Engineering, Arlington, NY, 1989.C. M. Harris, Handbook of Noise Control, McGraw-Hill, New York, 1979.C. H. Hansen, Understanding Active Noise Cancellation, Taylor it has to be computed from

32、sound pressure measurements. Acoustical energy is proportional to the square of sound pressure.Sound pressure level Lp (or SPL) in decibels, referenced to the approximate threshold of hearing, i.e., 2 x 10-5 Pascal (N/m2): 5-1025-10p 10 x 2plog2010 x 2plog10L (Eq. 1)where: p = sound pressure in PaSo

33、und power level Lw (or PWL) in decibels, referenced to 10-12 watt, is defined as: 12-10W 10Wlog10L (Eq. 4)where: W = sound power in wattWhenever the word level is used as a modifier for sound power or pressure, a reference power or pressure has to be given and the ratio between the measured quantity

34、 and the reference quantity is used to calculate the decibel level. The reference for sound power level must be noted since 10-13 watt is still often used. If the 10-13 watt reference is used, simply subtract 10 dB from the power level to obtain levels referenced to 10-12 watt.Figure 3 is a graphica

35、l representation of the pressure and power level formulas. When the pressure or power level changes, its ratio to the referenced value changes accordingly. For a 3 dB increase, the power ratio is doubled while a 6 dB increase in pressure level doubles the pressure ratio. About the smallest change th

36、e ear can detect is 1 or 2 dB. While stationary, 3 to 5 dB changes are detected, however, they are not detected walking from one area to another. A 10 dB noise increase would be perceived as twice as loud.SAE INTERNATIONAL AIR1826A Page 9 of 44Figure 3 - Sound pressure and pressure level ratios-20-1

37、00102030405060-10-5051015202530 0.11101001000R EL AT I VE PR ESSU R E L EVEL I N d b = 2 0 l o g 1 0(PR ESSU R E R AT I O )R EL AT I VE PO W ER L EVEL I N d b = 1 0 l o g 1 0(PO W ER R AT I O )RATIO(PRESSURE ORPOWER)SAE INTERNATIONAL AIR1826A Page 10 of 443.6 Decibel CalculationsThe ratio of the sou

38、nd power entering an element of a system to the sound power continuing beyond the element, expressed in decibels, is called the attenuation of that element: ce10WWlog10db)(innAttenuatio (Eq. 5)where: We = Sound power entering, wattWc = Sound power continuing, wattFigure 3 may be used to convert the

39、ratio of sound power to decibels and vice versa. If an attenuator absorbs 99.9% of the entering sound power, the power ratio is 100/0.1 = 1000, and the attenuation is 30 dB. Since this is relative, no reference is necessary. If referenced decibel levels are used, the attenuator equation reduces to a

40、 simple arithmetic expression:WcWe LLdb)(innAttenuatio (Eq. 6)where: LWe = sound power level entering (dB)LWc = sound power level continuing (dB)The attenuation of a group of elements through which the sound passes in succession is the arithmetic sum of all individual attenuation values in decibels.

41、 When the decibel system is used, the levels of two or more sounds cannot be added or subtracted arithmetically. The following equation can be used to combine levels: i10L10i10log10L (Eq. 7)where:Li = ith level to be combinedA graphical method can also be used to combine two sound levels at a time.

42、If more than two levels are to be combined, the two highest levels should be combined, and then the resulting value combined with the next highest level.Rearranging terms from Equation 7 for the case of only two levels, the following formula can be derived: 10X10 101log10Y (Eq. 8)where:X (in dB) = a

43、rithmetic difference between the two sound levels to be combined (larger minus smaller).Y (in dB) = amount to be arithmetically added to the larger sound level to be combined in order to obtain the sum of the two levels.Equation 8 can then be plotted to get Figure 4 which correlates Y to X.SAE INTER

44、NATIONAL AIR1826A Page 11 of 44Figure 4 - Chart for combining levelsExample calculations:Given LW1 = 86 dB and LW2 = 80 dB, their arithmetical difference is X = 6 dB. From either Equation 8 or Figure 4 it follows that Y = 0.97, so to obtain the sum of the two sound levels (LW1 amplified by LW2) we a

45、dd Y to LW1, or LW = LW1 + Y = 86.97 dB.SAE INTERNATIONAL AIR1826A Page 12 of 443.7 Comparative Levels of Common SoundsTable 2 - Comparative levels of common soundsSound PressureLevel Sound Pressure Common Sounds and Qualitative Perception(dB) (Pa) (psi)160 2 x 103 3 x 10-1 Medium Jet Engine140 2 x

46、102 3 x 10-2Large Propeller Aircraft-Air Raid Siren-Riveting130 64 9.6 x 10-3 Pain threshold120 20 3 x 10-3 Discotheque100 2 3 x 10-4Very noisyHeavy City TrafficSubway80 2 x 10-1 3 x 10-5 Busy Office70 6.4 x 10-2 9.6 x 10-6 Noisy60 2 x 10-2 3 x 10-6 Normal Speech at 1 m40 2 x 10-3 3 x 10-7QuietQuiet

47、 ResidentialNeighborhood20 2 x 10-4 3 x 10-8 Whisper0 2 x 10-5 3 x 10-9Barely AudibleThreshold ofHearing for a childFor the definition of the Sound Pressure Level (Lp) see Equation 3.4. DESIGN APPROACHTo reduce the ECS noise in the aircraft interior, two approaches are possible, source reductions an

48、d transmission path attenuations. In order to reduce noise at the source, it is necessary to identify the components or parts of the system generating the noise and to determine the mechanism of the sound generation process. Modifications may then be designed as appropriate. When all available steps have been taken to reduce noise at the source, any further improvement must come from the addition of insulation, absorption, or other treatments into the path between source and cabin. This requires that the dominant sound transmission path be determined, i.e., either str