Module 4 Flashcards
any undesirable or unwanted sound
noise
In the ______, the first-generation jet aircrafts led to a rapid expansion in commercial aviation with their ______ creating significant noise which severely disrupted the living patterns in nearby communities.
1950s, engines
In the ______, the U.S. Federal Aviation Administration (FAA) introduced the first noise certification standards and the International Civil Aviation Organization (ICAO) promoted similar standards globally (Smith, 1989).
1970s
What is Annex 16?
Environmental Protection
defined noise standards for aircraft certified before October 6, 1977
Annex 16 Chapter 2
defined noise standards for aircraft certified between October 6, 1977 and December 31, 2005
Annex 16 Chapter 3
defined noise standards for aircraft certified after December 31, 2005
Annex 16 Chapter 4
corresponds to ICAO Chapters 2/3/4
US FAR Part 36 Stages 2/3/4
Each new ICAO chapter imposes increasingly stringent noise limits, resulting in a ____ to ____ cumulative reduction in allowable noise.
10 to 20-dB
Two General Sources of Aircraft Noise
engines, airframe
Aviation Noise Sources
turbofan engine noise, turboprop engine noise, airframe noise, engine noise
It comes from the flow of air through and rapid rotations of the various components of the engine fan and core elements, as well as the high-speed gases in the engine exhaust being expelled into the outside air.
Turbofan Engine Noise (including APU noise)
This includes the turbulent air shed from each blade and the interactions between the blades.
Turboprop (Propeller) Noise
It is caused by the flow of air over the surfaces of the aircraft and the turbulent flows created by the structure and cavities introduced by the deployment of high-lift devices and landing gear.
Airframe Noise
It tends to dominate on the ground, especially during takeoff when the engines are at very high thrust level, on landing when using thrust reversers and when taxiing at low speed.
Engine Noise
It is created when the aircraft is flying at supersonic speeds which can be very disruptive to activities on the ground.
Sonic Boom
This issue severely limited the market for supersonic commercial aircraft introduced in the 1970s.
Sonic Boom
Only the ________ found a niche market serving transatlantic routes until its retirement in 2003 on economic grounds.
Aerospatiale-BAC Concorde
It is the ratio between the amount of air drawn in by the fan that bypasses the engine core relative to that passing through the core.
Bypass Ratio
Bypass ratio of large modem turbofan engines
10:1
This configuration achieves a given thrust level with minimum size of core and the slower moving bypass air mixes with the high-speed core air, resulting in a significantly lower exhaust velocity that in turn reduces exhaust noise.
large modem turbofan engines
near-term suggested solutions
engine core, nacelle chevrons, streamlined landing gear fairings
medium-term suggested solutions
geared turbofans, ultrahigh bypass ratio engines (unducted fan)
long-term suggested solutions
more integrated airframe/engine designs such as blended-wing body configurations
transmitted from a source through the air in waves
sound
It is sensitive to sound pressure.
human auditory system
The loudest sound a normal person can hear is approximately ____ times the RMS sound pressure of the faintest sound noticeable.
1 million
Its functions are:
- To address the limitations of using unweighted sound pressure levels in assessing the impact of noise on human perception and well-being.
- To provide a more accurate representation of how humans experience noise
The A-Weighted Sound Level
defined as a scalar quantity used to indicate the amplitude level of sound at a specific location in space
sound pressure
It is the deviation from the ambient atmospheric pressure and is caused by a sound wave
sound pressure
depends on the distance the measurement is taken from and in what atmospheric environment it is taken in
sound pressure
are not a unit of measure but a logarithmic function which indicates the ratio between two values
decibels
when the range of the sound pressure is expressed in decibels it is referred to as ______
sound pressure level
refers to the assessment and management of the impact of aircraft noise on the surrounding land uses
Aircraft Noise and Land-Use Compatibility