777 

Federal Aviation Administration, DOT 

Pt. 36, App. A 

A

PPENDIX

A 

TO

P

ART

36—A

IRCRAFT

 

N

OISE

M

EASUREMENT AND

E

VALUA

-

TION

U

NDER

§ 36.101 

Sec. 

A36.1 

Introduction. 

A36.2 

Noise Certification Test and Measurement 

Conditions. 

A36.3 

Measurement of Airplane Noise Received 

on the Ground. 

A36.4 

Calculations of Effective Perceived Noise 

Level From Measured Data. 

A36.5 

Reporting of Data to the FAA. 

A36.6 

Nomenclature: Symbols and Units. 

A36.7 

Sound Attenuation in Air. 

A36.8 [Reserved] 
A36.9 

Adjustment of Airplane Flight Test Re-

sults. 

Section A36.1 Introduction 

A36.1.1 This appendix prescribes the condi-

tions under which airplane noise certifi-
cation tests must be conducted and states 
the measurement procedures that must be 
used to measure airplane noise. The proce-
dures that must be used to determine the 
noise evaluation quantity designated as ef-
fective perceived noise level, EPNL, under 
§§ 36.101 and 36.803 are also stated. 

A36.1.2 The instructions and procedures 

given are intended to ensure uniformity dur-
ing compliance tests and to permit compari-
son between tests of various types of air-
planes conducted in various geographical lo-
cations. 

A36.1.3 A complete list of symbols and 

units, the mathematical formulation of per-
ceived noisiness, a procedure for determining 
atmospheric attenuation of sound, and de-
tailed procedures for correcting noise levels 
from non-reference to reference conditions 
are included in this appendix. 

A36.1.4 For Stage 4 airplanes, an acceptable 

alternative for noise measurement and eval-
uation is Appendix 2 to ICAO Annex 16, Vol-
ume I, Amendment 7 (incorporated by ref-
erence, see § 36.6). 

A36.1.5 For Stage 5 airplanes, an acceptable 

alternative for noise measurement and eval-
uation is Appendix 2 to ICAO Annex 16, Vol-
ume 1, Amendment 11–B (incorporated by 
reference, see § 36.6). 

Section A36.2 Noise Certification Test and 

Measurement Conditions 

A36.2.1 

General. 

A36.2.1.1 This section prescribes the condi-

tions under which noise certification must 
be conducted and the measurement proce-
dures that must be used. 

N

OTE

: Many noise certifications involve 

only minor changes to the airplane type de-
sign. The resulting changes in noise can 
often be established reliably without resort-
ing to a complete test as outlined in this ap-
pendix. For this reason, the FAA permits the 

use of approved equivalent procedures. There 
are also equivalent procedures that may be 
used in full certification tests, in the inter-
est of reducing costs and providing reliable 
results. Guidance material on the use of 
equivalent procedures in the noise certifi-
cation of subsonic jet and propeller-driven 
large airplanes is provided in the current ad-
visory circular for this part. 

A36.2.2 

Test environment. 

A36.2.2.1 Locations for measuring noise 

from an airplane in flight must be sur-
rounded by relatively flat terrain having no 
excessive sound absorption characteristics 
such as might be caused by thick, matted, or 
tall grass, shrubs, or wooded areas. No ob-
structions that significantly influence the 
sound field from the airplane must exist 
within a conical space above the point on the 
ground vertically below the microphone, the 
cone being defined by an axis normal to the 
ground and by a half-angle 80

° 

from this axis. 

N

OTE

: Those people carrying out the meas-

urements could themselves constitute such 
obstruction. 

A36.2.2.2 The tests must be carried out 

under the following atmospheric conditions. 

(a) No precipitation; 
(b) Ambient air temperature not above 95 

°

F (35 

°

C) and not below 14 

°

F (

¥

10 

°

C), and 

relative humidity not above 95% and not 
below 20% over the whole noise path between 
a point 33 ft (10 m) above the ground and the 
airplane; 

N

OTE

: Care should be taken to ensure that 

the noise measuring, airplane flight path 
tracking, and meteorological instrumenta-
tion are also operated within their specific 
environmental limitations. 

(c) Relative humidity and ambient tem-

perature over the whole noise path between 
a point 33 ft (10 m) above the ground and the 
airplane such that the sound attenuation in 
the one-third octave band centered on 8 kHz 
will not be more than 12 dB/100 m unless: 

(1) The dew point and dry bulb tempera-

tures are measured with a device which is ac-
curate to 

±

0.9 

°

F (

±

0.5 

°

C) and used to obtain 

relative humidity; in addition layered sec-
tions of the atmosphere are used as described 
in section A36.2.2.3 to compute equivalent 
weighted sound attenuations in each one- 
third octave band; or 

(2) The peak noy values at the time of 

PNLT, after adjustment to reference condi-
tions, occur at frequencies less than or equal 
to 400 Hz.; 

(d) If the atmospheric absorption coeffi-

cients vary over the PNLTM sound propaga-
tion path by more than 

±

1.6 dB/1000 ft (

±

0.5 

dB/100m) in the 3150Hz one-third octave band 
from the value of the absorption coefficient 
derived from the meteorological measure-
ment obtained at 33 ft (10 m) above the sur-
face, ‘‘layered’’ sections of the atmosphere 
must be used as described in section A36.2.2.3 

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