APPENDIX A
APPENDIX A
TABULATION OF ONE-THIRD OCTAVE BAND DATA
The data presented in the following two tables (Tables A-IA and A-IB) are the maximum
one-third octave band levels attained during the associated flyover corrected to an altitude
of 152.4 meters (500 feet). The correction to a constant altitude involved the application
of both spherical spreading and atmospheric absorption effects. In the case of the Prue-2
glider data, corrections were also applied for the ambient noise by the method of energy
subtraction. Several of the glider data band levels fell below the corresponding band
levels of the measured ambient noise, erroneously indicating the absence of data. This is
due to the low frequency variability of the ambient noise. In these cases the band levels
were obtained by linear interpolation between the adjacent bands, and are denoted by
parenthesis in the tabulation.
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APPENDIX B
APPENDIX B VARIATIONS ON A THEME OF AERODYNAMIC NOISE The equations developed herein for predicting the level of the far-field aerodynamic noise can also be expressed in other forms. One such form, somewhat more suitable to aircraft design work, incorporates the terms for the coefficient of lift, C. , and wing load- ing, W/S, in these equations. The results for both the idealized and actual data, respec- tively, are: OASPL = 10 log (Bla) ,-?- H*7 +32.8 35.9 (Bib) OASPL = 10 log •j where the constant (2/p) has been incorporated into the constant term. In the foregoing equation the terms Ct and W/S are expressed separately in order to emphasize their rela- tive importance in the total expression.
Throughout this report SI units have been used. By rewriting equations 6 or 8 in the following generalized form (B2) OASPL = 10 log AR4
V /J
different units can be used with only a change in the value of K. The following table presents K values for different sets of units for both the idealized and actual data as well as the "mean" value for use with equation 8.
CONSTANT (K) "Mean" V S r Idealized Actual 12.2 10.7 knots ft ft 9.1 ft/sec ft ft -1.4 -3.0 -4.5 It is interesting to note that the constant in equation 5 is unaffected by a change of units providing a consistent set of units is used since S -r r is dimensionless.
APPENDIX C
APPENDIX C CONVERSION FACTORS The following table, based on reference 12, is presented for the convenience of the reader.
To Convert Tp_ Multiply By dynes/sq cm .1 newtons/sq m feet .3048 meters feet/sec meters/sec .3048 knots meters/sec .51444444 pounds (force) 4.4482216 newtons slugs/cu ft kg/cu m 515.379 sq ft sq m .09290304
APPENDIX D
APPENDIX D COMPARISON WITH RECENT DATA ON THE C-5A GALAXY In January 1973 a series of flights with the C-5A Galaxy were made by the Lockheed- Georgia Company for the purpose of measuring far-field aerodynamic noise under a variety of aircraft configurations. These data are beinq prepared under a NASA contract for pub- lication as a Contractor's Report (ref. 4). The flights were made with the engines operating at the flight idle setting. One of these flights was made with the aircraft in a "clean" configuration. The portion of the total vehicle noise spectrum attributed to the far-field aerodynamic noise was that below approximately 400 Hz. The measured data, adjusted to an altitude of 91.44 m (300 ft), are presented in the following table along with the corresponding idealized spectrum values. The idealized values, indicated by paren- theses in the table, were obtained by extrapolating the drop-off between the 63 and 80 Hz bands to the 50 Hz band and the drop-off between the 160 and 200 Hz bands to the 250 315, and 400 Hz bands. The energy summation of these 10 third-octave bands is also presented.
Measured Idealized Frequency (Hz) Data Data 50 (68) 79 79 90 90 95 95 125 95 160 93 93 200 87 87 250 89 (81) 315 82 ' (75) 400 81 (69) 100.0 OASPL 100.4 (50 - 400 Hz) The corresponding test condition aircraft dimensional data are: 2 713 415N (608 000 Ib) Gross weight: Wing area: 576 sq m (6200 sq ft) Aspect ratio: 8.0 Altitude: 91.44m (300ft) 101.9m/sec (198 knots) Velocity: The OASPL calculated by equation 8, considered more suitable for predicting the aerodynamic noise from current transport aircraft, is 100.9 dB while that calculated by equation 6a for the idealized spectrum is 99.3 dB. The remarkable accuracy of this sizeable extrapolation, 0.5 to 0.7 dB, verifies the essential validity of the analysis and permits such extrapolations with a reasonably high level of confidence.
REFERENCES 1. Gibson, J. S.: The Ultimate Noise Barrier. Proceedings of the Institute of Noise Control Engineering (Inter-Noise 72), October 1972, pp. 332-337.
2. Blumenthal, V. L; et al.: Aircraft Environmental Problems. Paper 73-5, Am. Inst.
Aeron. and Astronaut, January 1973.
3. Gibson, J. S.: Non-Engine Aerodynamic Noise: The Limit to Aircraft Noise Reduction. Paper F22Y12, Proceedings of the Institute of Noise Control Engineering (Inter-Noise 73), August 1973, pp. 445-454.
4. Gibson, J. S.: Non-Engine Aerodynamic Noise Investigation Of A Large Aircraft, NASA CR-2378, 1974 .
5. Gibbs, J. B.; and Healy, G. J.: Noise From A Gliding DC-3, Report LR 23328, Lockheed-California Company, March 15, 1970.
6. Brooks, P . W . : The World's Airliners, Putnam and Company (London), 1962, pp. 143-149; 211-217.
7. Anon.: Sales Brochure 1969, Aero-Commander Division, North American Rockwell' Company.
8. Anon.: The World's Sailplanes. OSTI Vand Swiss Aero Review, Regina-Druck (Zurich, Switzerland).
9. Anon.: Owners Manual 1967. Cessna Corporation.
10. Anon.: Standard Values of Atmospheric Absorption as a Function of Temperature and Humidity for Use in Evaluating Aircraft Flyover Noise, Society of Automotive Engineers, ARP-866, 1964.
11. Morse, P. M.; and Ingard, K. U.: Theoretical Acoustics, McGraw-Hill Book Company, Inc., 1968, pg. 762.
12. Mechtly, E. A.: The International System of Units, NASA SP-7012, 1973.
NASA-Langley, 1974 CR~2377 63 N A T I O N A L A E R O N A U T I C S A N D S P A C E A D M I N I S T R A T I O N WASHINGTON. D.C. 2OS46 POSTAGE AND FEES PAID IATIONAL AERONAUTICS AND SPACE ADMINISTRATION OFFICIAL BUSINESS SPECIAL FOURTH-CLASS RATE BOOK I f I ' l l i l "The aeronautical and i, itics of the United States shall be conducted so as to contribut owl- mena in the atnu, '.'he Administration shall practicable and appropriate dissemination of infor/> its activities and tl thereof" —NATIONAL AERONAUTICS AND SPACE ACT OF 1958
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