Two computer programs aid aircraft designers who need to identify noise characteristics of various aircraft and engine configurations; calculated noise levels can then be compared with community goals for noise limitation

Peart, N. A.

English

NASA Technical Reports Server

April 1975	 B75-10060 
NASA TECH BRIEF 
Ames Research Center	
_4r 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Prediction of Aircraft Noise Source and Estimation
of Noise-Level Contours 
. 
Two computer programs have been developed to 
aid aircraft designers who need to identify the noise 
characteristics of various aircraft and engine config-
urations; the calculated noise levels can then be com-
pared with community goals for noise limitation. The 
first program is used to predict the noise generated by 
five basic types of aircraft: turbojet, turbofan, turbo-
prop, V/STOL, and helicopter. The second program 
is used to calculate contours of equal noise level 
(footprints) and the area within the contours for an 
aircraft during takeoff and approach operations; a 
second version of the footprint program is compatible 
with a flight simulator which provides aerodynamic 
and engine performance data, and thus an estimate 
can be made of the noise exposure produced by an 
aircraft operation. 
The first program has been generalized to accom-
modate several different types of noise sources as-
sociated with current and future aircraft. The noise-
source prediction modules include: measured data, 
jet noise, core and turbine noise, compressor and fan 
noise, and propeller, helicopter, and tilt rotor noise. 
The four steps in the program which provide the 
flexibility required for predicting the noise from 
several sources are solution of flight path/observer 
geometry, calculation and summation of the sound 
levels for each source, extrapolation of the index 
noise spectra to the observer, and calculation of 
human response measures. One of the requirements 
of the noise prediction program is the linkage of its 
output, a data table, with the noise contour program. 
Output variables for the data table are noise level, 
engine performance parameter, elevation angle in
degrees, and logarithm (log R) of the range at the 
closest point of approach. 
A noise contour is the locus of points on the 
ground in which the noise is at a constant acoustic 
level; its calculation requires the establishment of 
the relationship between the aircraft's noise perform-
ance and the aero/propulsion parameters during 
takeoff and landing. The noise contour calculation 
can also be outlined into four basic steps: formation 
of the acoustic data functions, calculation of log R 
for a specific contour, calculation of contour points, 
and coordinate transformations. 
Notes: 
1. The programs are written in FORTRAN 0 for 
use with an IBM 360 computer. The second ver-
sion of the noise contour program, for use with a 
flight simulator, is written in FORTRAN G for 
Sigma VII and VIII computers. 
2. Inquiries concerning these programs should be 
directed to: 
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: ARC-10880. 
Source: Noel A. Peart of 
Boeing Commercial Airplane Company
under contract to
Ames Research Center
(ARC-10880) 
.
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Category 09 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Prediction of aircraft noise source and estimation of noise-level contours

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