Introduction to Acoustics

990 Part G Structural Acoustics and Noise
Part G 23.2
The first issue of 14CFR part 36 became effective
in 1969; ICAO annex 16 was first issued in 1971. The
main objective of those regulations was to ensure that
noise produced by new aircraft designs would be less
than the noise produced by earlier designs. In the years
since the initial issue, the certification noise level limits
have been gradually reduced in stages.
Stage 1 airplanes are the noisiest, and include the
as-manufactured versions of the Boeing 707 and Mc-
Donnell Douglas DC8 and various business/executive
jets. Stage-2-compliant airplanes have lower noise levels
than stage 1 airplanes. Noise levels from airplanes
that comply with stage 3 requirements are even lower.
An airplane that complies with the Stage 1, 2, or 3 requirements
of 14CFR Part 36 also complies with the
corresponding Chap. 1, 2 or 3 requirements of ICAO
Annex 16.
ICAO Annex 16 recently introduced the Chapter
4 requirements for jet-propelled airplanes and for
propeller-driven airplanes having a takeoff gross mass
of more than 8618 kg. The FAA is considering adoption
of similar stage 4 requirements. Noise-level limits
for chapter 4 compliance are the same as for chapter
3 compliance but compliance was made more
stringent by eliminating the tradeoff provisions that had
Noise level, EPNdB (1500' sideline)
120
110
100
90
1950
B-52
Comet 4
Turbojet
707-100
720
DC8-20
707-300B
Caravelle
First generation
turbofan
1960
CV990A
CV880-22
727-100
DC8-61
BAC-111
DC9-10
727-200
747-100
737-100
737-200
747-200
DC10-10
1970
been part of the chapter 2 and 3 (or stage 2 and 3)
requirements.
As an example of the changes to the certification
noise-level limits, the effective perceived noise level
limit at the lateral position for a takeoff gross mass
of 200 000 kg (441 000 lbf) is 107.1 dB for a chapter
2/stage 2 airplane at 650 m to the side of the takeoff
flight path, and 100.4 dB for a chapter 3/stage 3 airplane
(or a chapter 4 airplane) at 450 m to the side of
the takeoff flight path. Changes in lateral noise levels
are representative of improvements in the technology of
aircraft noise reduction.
Figure 23.19 illustrates trends in the progress in reducing
the noise emission from commercial jet aircraft.
There are no chapter 1/stage 1 airplanes operating in
most of the industrialized countries of the world and
only a few chapter 2/stage 2 airplanes.
For jet-powered and propeller-driven airplanes, the
engines are the principal sources of noise during ground
roll, climb-out, and landing. Sound produced by vortices
shed by the extended landing gear and by wing
leading-and trailing-edge devices (flaps) contributes to
the noise level under landing-approach flight paths,
and is an important consideration as engine noise is
reduced.
• Normalized to 100 000 lb thrust
• Noise levels are for airplane/engine
configurations at time of initial service
Second generation turbofan
MD80
747-300
A300B2-101
A310-300
A320-100
767-300
A321
DC10-30
L-1011 767-200
BAC-146-200
737-200
737-300
747-400 737-500
A330
777-200
A340
MD90-30
MD-11
1980
1990 1995
Year of initial service
Fig. 23.19 Progress in aircraft noise reduction. Effective perceived noise level at the 450 m lateral noise-measurement
point normalized to a total static thrust of 444 800 N for the noted airplane/engine configurations at the time of initial
service. (After Willshire [23.110]; adopted from Condit [23.111])