COpy b Report No. FAA"lP-75-10o.

FAA WJH Technical Center

IiiDIIIIInt11111W1IIU I11l 00090318

x'1, EFFECT OF TEMPERATURE AND HUMIDITY ON ,\ . ."

~j AIRCRAFT NOISE PROPAGATION

'JB' McCollough

NAFEe Harold C. True LIBRARY

Septem ber 1975

Final Report

Document is available to the public through the National Technical Information Service,

Springfield, Virginia 22161.

Prepared By

u.s. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION

Systems Research & Development Service Washington, D.C. 20590

~ ,.

NOTICE

This document is disseminated under the sponsorship of the Department of Transpcrtation in the interest ,of info~etjon ~Y-chcnge. The Uni~ed Stat~s Government assumes no liability for its contents or use thereof.

...

Technical Report Documentation Page

2. Government Accession No.1. Report No.

FAA-RD-75-l00 4. Title and Subtitle

Effect of Temperature and Humidity On Aircraft Noise Propagation

'-, h::------;-,------------------------------

1_ Author's)

'JB' McCollough and Harold C. True

1S. Supplementary Notes

16. Abstract

3. Recipient's Catalog No.

5. Report Dote

September 1975 6. Performing Orgonization Code

8. Performing OrganizQtion Report No.

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

FINAL REPORT

14. Sponsoring Agency Code

I This report presents the results of a test program conducted to measure the effect of varying meteorological conditions on aircraft flyover noise levels. Detailed temperature and humidity data were obtained using an instrument system carried by a light aircraft. High and low altitude inversions as well as standard lapse rate atmospheres were investigated. Level flyovers were conducted, using a DC-9-l0 aircraft operated at a thrust (Fn/Il of 6,000 lbs., as a constant noise source. Measured noise levels varied up to 4 EPNdB depending upon the absorptive properties of the atmosphere. Several analysis procedures were investigated in an effort to correct noise data for weather conditions. Weather correction procedures based on single point meteorological data were inadequate to normalize, to reference conditions, the noise data for those conditions with non-uniform temperature and humidity profiles. A layered analysis procedure, however, normalized all flyover noise levels to those levels taken under near reference conditions. The layered analysis procedure incrementally adjusts the measured peak spectra based on the acoustic absorption in each increment. These results indicated that noise certification testing under non-uniform temperature and humidity conditions could, if allowed, be conducted provided that frequent and detailed meteorological data is available and the layered weather correction procedure is used.

rKey Words Aircraft !,Toise Levels; Atmospheric Acoustic Absorption: I Meteorological Conditions:

Temperature, Humidity: Level Fl' iers Layered Analysis . : ~., .

18. Oi stri bution Statement

Document is available to the publicthrough the National Technical Information Service Springfield, Virginia 22151

Securi ty Closs; f. (of thi S report) 21. No. of Pages 22. Price20. ~"curity Clossif. (of this page)M

105UNCLASSIFIED UNCLASSIFIED

-- _._----- -. him DOT F 1700.7 (8-72) Re;>roduction of completed page authorized

i

ACKNOWLEDGEMENTS

This program was conducted by the Federal Aviation Administration, Washington, D.C. Due to the size and scope of this program, a number of FAA offices and services were involved as were several other government agencies and private contractors. The success of the program is due to the contribution of the following participants:

FAA/Office of Environmental Quality - identification of program requirement

FAA/Systems Research and Development Service, Aircraft Safety and Noise Abatement Division - overall program management, test direction and data analysis

FAA/Academy - noise source aircraft, flight crew and support crews

FAA/National Aviation Facilities Experimental Center meteorological sounding aircraft and flight crew

FAA/Western Region - flight test engineer, acoustic consulting and test site operations support

NASA/Langley Research Center - noise measurement equipment, atmospheric acoustic sounding and technical support

NCAR/National Committee for Atmospheric Research,-Boulder, Colorado - Kytoon atmospheric sounder and crew

u. S. Army Proving Grounds, Yuma, Arizona - lower atmospheric wind measurements at Yuma, Arizona

Noise and Vibration Control Corporation - test site computer analysis of as measured data and test program computer data reduction

Wyle Laboratories (Subcontractor to NASA) - noise recording

U. S. Marine Corps Air Station, Yuma, Arizona - test site operation support at Yuma, Arizona.

ii

TABLE OF CONTENTS

PAGE

Abstract i Acknowledgements ii List of Tables iv List of Figures v Abbreviations and Symbols vii Metric Conversion Factors x Summary 1

i.o Introduction 7

2.0 Test Program 8 2.1 Noise Measurement 8 2.2 Noise Source 2 . 3 Meteorological Data 2.4 Test Sites 10

3.0 Data Reduction 11

4.0 Description of Noise Measurement System 12

5.0 Discussion of Results 17 5.1 Effect of Low Altitude Inversion, 17

1100 Foot Flight Altitude 5.2 Effect of Low Altitude Inversion, 3S

2000 Foot Flight Altitude 5.3 Effect of Flying at or Below a High Altitude 49

Inversion 5.4 Baseline Noise, Thrust, Altitude EPNL Data 58 5.5 Data Summary

6.0 References 7S

Appendix A - Noise Measurement System Specifications 76

99

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TABLE NO.

1

2

3

4

5

LIST OF TABLES

TITLE

Summary of Average Noise Level Under Varying Meteorological Conditions

Effect of Weather and Weather Correction Method, Low Inversion, Flight Altitude = 1100 feet

Effect of Weather and Weather Correction Method, Low Inversion, Flight Altitude = 2000 feet

Effect of Weather and Weather Correction Method, High Altitude Inversion, Flight Altitude = 1100 feet

Flyover Noise Data Summary

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PAGE

5

20

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37

50

67

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1 Normalization of F1yover Noise Data. Measured 4 and Corrected Spectra at time of PNLTM

- 2 proposed Wider Test Window 6 3 Frequency Dependance of Atmospheric Absorption 14

4 Effect of Roll-Off on Corrected Spectra 15

5 Acoustic and Meteorological Data Reduction 16

6 Temperature and Humidity Profile - Fresno 21 Baseline, 1100 Foot Flight Altitude

7 Temperature and Humidity Profile - Yuma Baseline, 22 1100 Foot Flight Altitude

8 Temperature and Humidity Profile - Hot and Dry, 23 No Inversion, 1100 Foot Flight Altitude

9 Temperature and Humidity Profile - Hot and Dry, 24 strong Inversion, 1100 Foot Flight Altitude

10 Temperature and Humidity Profile - Temperate, 25 Strong Inversion, 1100 Foot Flight Altitude

11 Temperature and Humidity Profile - Hot and Dry, 26 Weak Inversion, 1100 Foot Flight Altitude

12 Temperature and Humidity Profile - Weak Inversion, 27 Calm Winds, 1100 Foot Flight Altitude

13 Temperature and Humidity Profile - Weak Inversion, 28 Stronger Winds, 1100 Foot Flight Altitude

14 Wind Velocity and Direction 29

15 Altitude Attenuation Plot,' Low Altitude Inversions, 30 Flight Altitude = 1100 Feet

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16 FAA DC-9 PNLTM Spectra, Measured Data, Altitude = 31 1100 Feet

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FIGURE NO.

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30

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32

LIST OF FIGURES

TITLE

FAA DC-9 PNLTM Spectra, Baseline Weather Corrections Altitude = 1100 Feet

FAA DC-9 PNLTM Spectra, No Inversion, Hot and Dry Altitude = 1100 Feet

FAA DC-9 PNLTM Spectra, Strong Low Inversion Hot and Dry, Altitude = 1100 Feet

Temperature and Humidity Profile, Fresno Baseline, 2000 Foot Flight Altitude

Temperature and Humidity Profile, Hot and Dry, No Inversion, 2000 Foot Flight Altitude

Temperature and Humidity Profile - Temperate, Strong Inversion, 2000 Foot Flight Altitude

Temperature and Humidity Profile - Hot and Dry, Weak Inversion, 2000 Foot Flight Altitude

Temperature and Humidity Profile - Weak Inversion Calm Winds, 2000 Foot Flight Altitude

Temperature and Humidity Profile - Weak Inversion, Stronger Winds, 2000 Foot Flight Altitude

Altitude Attenuation Plot, Low Altitude Inversion, Flight Altitude = 2000 Feet

FAA DC-9 PNLTM Spectra, Measured Data, 2000 Foot Flight Altitude

FAA DC-9 PNLTM Spectra, Baseline Weather Corrections 2000 Foot Flight Altitude

FAA DC-9 PNLTM Spectra, No Inversion, Hot and Dry, 2000 Foot Flight Altitude

FAA DC-9 PNLTM Spectra, Weak Low Inversion, Hot and Dry, 2000 Foot Flight Altitude

Temperature and Humidity Profile, Baseline, 500 Foot Flight Altitude

Temperature and Humidity Profile - High Altitude Inversion, 500 Foot Flight Altitude

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FIGURE NO.

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LIST OF FIGURES

TITLE PAGE

Temperature and Humidity Profile, High A