Aircraft Noise: Sources, Effects and Trends

Aircraft Noise: Sources,
Effects and Trends
Kevin P. Shepherd
NASA Langley Research Center
Hampton VA
Aviation and the Environment: A Primer for North American Stakeholders

Aircraft Noise Sources
Landing Gear
Engine Sources
High-Lift Devices
Propulsion / Airframe
Interactions
Aircraft noise is a complex amalgam of sources and
airframe interactions.

Noise Level, EPNdB
100
95
90
85
80
75
70
Aircraft Noise Metrics
Approach
120 m
2000 m
Sideline
Populated Areas
6500 m
450 m
Takeoff / Cutback
Approach Sideline Cutback
Engine
Airframe
Total

Aircraft Noise Level Trend

Trend in Population within
Airport 65 DNL contours

Growth in Airport Noise “Actions”
Credit: Boeing

Noise is Airports’ Major
Environmental Concern

Effects of Aircraft Noise on People
Much studied and established:
• Speech interference (conversation, TV, radio)
• Sleep interference
• Interference with rest and relaxation
• Annoyance ( Σ Effects + other variables)
• Complaints
Indicative:
• Interference with learning (schools)
• Health (hypertension, myocardial infarction,
mental…)

Aircraft Noise Annoyance
• Annoyance, as determined from community
surveys, is the basis of (most) regulation and
guidance.
• Annoyance is:
– related to noise exposure (noise levels, # flyovers)
– strongly influenced by attitudes
– weakly influenced by demographic variables and
background (ambient) noise levels

Aircraft Noise Engenders Complaints
• Complaints are
– highly visible to airport operators
– not synonymous with annoyance
– generated from all noise level regions
– frequently triggered by individual events
• Complainants are not representative of
general population

Future Trends
“Aircraft noise is the most significant cause of
adverse community reaction…This is expected
to remain the case for the foreseeable future…”
- ICAO Environmental Report 2007

Quiet Technology Demonstrator 2
Boeing, GE, Goodrich, ANA, NASA and FAA
partnership for demonstrating advanced noise
reduction concepts.
Core
Chevrons
PAA Fan Chevrons
Integrated with
Airframe/Pylon
Spliceless
Inlet Liner
and Lip
Liner
Landing Gear Alignment
and Toboggan Fairing
Near Field
Holography
Diagnostics
for Interior
Noise

Continuous Descent Arrival
• CDA is designed to
minimize level flight
segments at low altitude
– Lower required thrust
– Increased distance between
aircraft and community
runway
Current-day
G/S intercept
CDA
G/S intercept
CDA with
conventional avionics
Area of Noise Benefit
Current-day
approach
trajectory

Likely Trends in Airport Noise and
Effects
• Increased flights in nighttime hours
– nighttime limits, sleep disturbance criteria
• Further studies of health effects
– evidence will accumulate
• Improved communication with communities
– clear and accurate descriptions of noise environment
and its effects
• Increased emphasis on “distant” communities
• Trends that might be relevant
– dramatic increases in telecommuting
– growth in “outdoor” living spaces

The Challenge
• Continued growth of air transportation
• Continued pressure from communities for
less noise
• Source noise reduction both difficult and
slow to affect fleet noise levels

Growth and Airport Noise Contour Areas
Scenario
5% annual growth in
# operations
(No change in fleet
mix/technology)
5% annual growth
4% annual fleet
replacement (in-hand
technology)
5% annual growth
4% annual fleet
replacement (new
technology*)
Annual Change
dB Contour area
0.21 3.8%
0.05 0.9%
-0.07 -1.2%
25 year change
dB Contour area
5.25 153%
1.25 26%
-1.75 -26%
* Assumes historical trend of 7dB/25 years

Concluding Observations
• Pressure for reduced airport noise will continue
• If future technology improvements match
historical trends then growth can probably be
accommodated with little or no net change in
noise exposure
• Significant reductions in noise exposure in the
presence of growth will be difficult
– new technology (source noise and ops)
– improved land use (lower “impact” thresholds)
– operating restrictions, phase-outs, and other such
measures