1、MIL-A-BBOhA 15 779b19Oh 0481750 8 MIL-A-8806A , 11 July 1060 Superseding 25 October 1956 MIL-A-8806(ASG) MILITARY SPECIFICATION ACOUSTICAL NOE LEVEL IN AIEKRAFT, GENERAL SPECIFICATION FOR This specification has been approved by the Department of Defense and is man- datory for use by the Departments
2、of the Army, the Navy, and the Air Force. 1. SCOPE 1.1 This specification covers the general requiremente for the control of acoustical noise in occupied spaces of aircraft, including the acceptable noise levels andsthe testing requiremente for determining conformance to these levels. 2. APPLICABLE-
3、DOCUMENTS 2.1 The following documents of the issue in effect on date of invitation for bids or request for proposal, form a part of this specification to the extent specified herein. SPECIFICATIONS Military MIL-S-3151 Sound-Level-Measuring Equipment MIL-S-6144 Soundproofing for Aircraft; General Spe
4、cification for lnstallation of MIL-1-7171 Insulation Blanket, Thermal-Acoustical (When requesting specifications, refer to both title and symbol. Copies of Specifications may be obtained upon application to the Commanding Officer, Naval Supply Depot, 6801 Tabor Avenue, Philadelphia, Pennsylvania, 19
5、120, Attention: Code 106);. - . - -% i I ,/ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3. REQUIREMENTS 3.1 Acoustical noise levels -$ 3.1.1 Maximum continuouls power - The mouetical noise level in . Provided by IHSNot for ResaleNo reproduction o
6、r networking permitted without license from IHS-,-,-MIL-A-8806A 35 9999906 0483752 3 MILA-8006A 3.1.8 a. Protective helmets - In aircraft in whioh personnel mut necessarily wear helmets ht all times ancl commtmioate by electronic meam (e. g. , single place fighter aircraft), . the acoustical noise l
7、evel (me 6.2.2) shall not exceed the values speoiiied in Table IllA referred)or Table III B during Oodtiona of “UM CONTIMJOUS POWER. .TABLE Dl, - Maximum aoceptable noise level with prtective helmets or deviam -” mA. 8 III. and to Air Force and Army aircraft procurement when so Btated in the airoraf
8、t detail epecfcation. TABLE W, - Maximum acceptable noise level at normal cruise power I Ill A. Frequenoy .(OPE) L Band . Overall 106 Overalf level (db) Center Max. accept- I., . Frequency bands I able noise 2 22.4 46 104 31.6 46 - 90 300. - 600 96 500 356 - 710 150 - 300 104 250 180 - 366 76 - 150
9、104 , 125 90 - 100 37.6 - 76 104 63 ,710 - 1400 1000 90 600 - 1200 1400 - 2800 2000 . 4800 - 9600 76 8000 6600 - 11200 2400 - 4800 76 4000 2800 * ,5600 1200 - 2400 86 ! Max. accept- able noise level (db) . 106 104 104 104 96 90 86 76 76 Provided by IHSNot for ResaleNo reproduction or networking perm
10、itted without license from IHS-,-,-MIL-A-BBObA L5 99999Ob 0483753 3 MIL-A-8806A 3.1.6 Auxiliary systems - The auxiliary systems which normally operate for longer than B minutes shall not produce an increase in noise levels in occupied compartments above the tables herein, Short duration noise levels
11、 shall not exceed levels in Table DA or Table DB unless specifically approved. 3.1.6 Special missions - For special missions such as Anti-Submarine Warfare (ASW), Aircraft Early Warning (AEW), and Electronio dounter Measures (ECM) which may require noise levels lower than those required by this spec
12、ifi- cation, the requirements will be so stated in the detail specification. 3.2 . Noise control.methods - 3.2.1 During the design and development stages of the aircraft, the contractor shall nclude in the design and, where pertinent, demonstrate the per- formance of ,those design. features necessar
13、y.to insure complihce with require4 noise levels, Such design features may include but are not iimted to prop phasing, jet noise suppressors, separation .of occupied areas from noise sources, relative placement of engines and fuselage,. and related items. 3.2.2 AcWJcal treatment - Where applicable,
14、soundproofing con- forming to Specification MIL-1-7171 shall be installed in accordance with Spec- ificatipn MIL-S-6144 to effect the specified levels. Acoustic treatments including other than flexible blankets shall be of approved types. 3.3 Reporta required - 3.3.1 Engineering report on noise cont
15、rol measures - me contractor“ shall fdsh an engineering report for approval by the procuring activity prior to fabrication of the prototype or major modification of an aircraft which shall in- clude the following material: (a) . Engineering estimates of-the noise to be developed inside the aircraft
16、and the engineering basis (pertinent structural data, tests, calculations, etc) for such estimates, ) Sketches and tables showing the type, total and unit weight, total area, construction , location, and method of fastening of all soundproofing to be installed to reduce noise to the levels heretofor
17、e required. (c) Estimates or measurements of noise levels generated by auxiliary systems. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-BBObA L5 I 99999Ob 0481754 5 MIL-A-8806A 8 3i3.2 Flight test noise level report - The contractor shall fur
18、nish a noise level measurement report prior to acceptance of the aircrdt, which shall include the following material: (a) A brief description of the noise level measuring equipment wed, (including microphones). ) Location of the microphones. (c) The recorded data in tabular or graphical form. (d) Te
19、st conditions under which the recording was made, (e) A brief description.of the soundproofing installed in ,c.* . -r. the test aircraft. 4. QUALITY ASSURANCE PROVISIONS 4.1 a Samplinq - Acoustic noise level measurementa shall be made on each experimental airbraft, and on an early model of each prod
20、uction aircraft . or modfication thereof. 4.2 Test conditions - Acoustical noise level measurements shall be made under the followfng conditfons;. 4,201 Test Equipment - Measurements shall be obtained with noise level measuring equipment demonstrated to be substantially in accordance with the perfor
21、mance requirements of Specification MIES-3161. The test equipment including the microphone, shall be calibrated throughout the frequency range of we. The calibration shall be applied in reporting the results in each octave band. .- 4.2.2 Stations - Measurements shall be made near the head levels of
22、all crew stations and of a representative number of passenger stations. The stations selected for measurements shall be subject to the -approval of the pro- curing activity; additional stations may be required if considered necessary. Measurement6 shall be made for a sufficient peripd of time to per
23、mit a sampling of minimum and maximum levels by octave band. 4.2.3 Altitude - Except as specified in 3.1.2, measurements shall be obtained with the aircraft in level forward flight at the lowest altitude suffi- oient to insure the mcixmum pressure differential between the cabin and the ex- ternal at
24、morpbsrio preasure. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-880bA L5 9961990b 0481755 7 MIL-A-8806A (a) For combat aircraft, measurements shall be made at I both normal and combat pressure differentials, ) If the aircraft is not pressur
25、ized, the altitude shall be the highest at which maximum control power can be obtained, provided this altitude does not exceed 12,000 ft, 4.2.4 Power conditions - (a) In order to determine compliance with 3.1.1 and 3.1.3, the aircraft shall be operated at maximum continuous. power with all auxiliary
26、 systems, which normally operab for more than 5 minutes,. in full operation. (b) In order to determine compliance with 3.1.4, the air- craft shall be operated at norma cruise power with all auxiliary systems, which normally operate for more than 5 minutes, in full operation. (6) In order to determin
27、e compliance with 3.1.2, the aircraft shall be operated under the appropriate flight conditions which maximize the resulting acoustical noise. 5. PREPARATION FOR DELIVERY 6.1 . This section is not applicable to this specification. 6. NOTES 6.1 Intended use - This specification defines the general re
28、quire- menta for the control of acoustical noise in occupied spaces of aircraft, includipg the acceptable noise leve18, and the testing requirements for determining coa- fomance to these levels. 6.2 Definition - 6.261 Acoustio reference level - The reference sound pressure level for measurementa mad
29、e in accordamzt with this specification will be the level produced by a sound preeeure of 0.0002 dyne/cm2. 6.2.2 Acoustical noise level - The acoustical noise level of the air- craft shall be considered to be the numerical average of the measured minimum and Provided by IHSNot for ResaleNo reproduct
30、ion or networking permitted without license from IHS-,-,-NIL-A-8BObA 15 993990b 048l175b 9 E 1 MIL-A-8806A a maximum levels, provided this average is not less than 3 db below the maximum. In the latter case the reported level sel be the maximum less 3 db. 6.2,3 Overall acoustical noise level - The t
31、erm overall acoustical noise level wffl be interpreted as including all noise within the frequency range from 22.4 to 11200 cycles per second. 6.2.4 Maximum oontinuow power - Maxlmwn continuous power is the maximum power that the engine can develop for continuous operation in level flight at the alt
32、itude where measurements are to be taken. 6.2.5 Normal cruise power - Normal cruise power is the power the engine can develop for maximum range in level flight at the altitude where measurements are to be taken, f 6.246 Auxiliary systems - An auxiliary system is any mechanism or structure other than
33、 the airframe or power plant which performs a function at some time during the operation d the aircraft, e,g, heat and vent, pressuri- zation, defrost and defog, inverters, pumps, Auxiliary Power Unit (APU), etc. 6.3 The noise level tables were developed from consideration of damage to hearing, spee
34、ch communication requirements, and effect8 on crew performance, It is recognized that these levels represent a compromise between those desired and those considered attainable within the state of the art of noise control in aircraft. This compromise considere the noise characteristics of present tur
35、bojet, turboprop, and piston-driven aircraft. Custodians: Ariny - MO Navy - A8 Air Force - 11 Reviewers: Army - MO Navy - AS Air Force - 11 Preparing Activity: NaVY - A8 (Project 1500 - 0054) Users: Navy - MC, CG Review/user information is current as of the date of this document. For future coordination of changes to this document, draft circulation should be based on the information in the current DODISS. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
