Book 2 - Engine Noise Reduction

Question 1

three methods of reducing noise from a jet engine:

• use a _______ throttle setting (thrust/power) for take off
• wrap the engine in a noise __________ material
• reduce the velocity of the jet ______ or increase the velocity of the ambient air at the exhaust

Answer 1

three methods of reducing noise from a jet engine:

• use a LOWER throttle setting (thrust/power) for take off
• wrap the engine in a noise INSULATING material
• reduce the velocity of the jet EFFLUX or increase the velocity of the ambient air at the exhaust

Question 2

noise from the jet efflux is caused by the difference in air speeds at the exhaust, creating __________. the turbulence consists of _______. many small eddies, close to the jet pipe produce ____ pitched noise, the eddies getting progressively larger and producing an increasingly ___ pitched noise with __________ distance from the jet pipe

Answer 2

noise from the jet efflux is caused by the difference in air speeds at the exhaust, creating TURBULENCE. the turbulence consists of EDDIES. many small eddies, close to the jet pipe produce HIGH pitched noise, the eddies getting progressively larger and producing an increasingly LOW pitched noise with INCREASING distance from the jet pipe

Question 3

engine noise levels are described using EPNdB or ________ ________ ______ in decibels

Answer 3

engine noise levels are described using EPNdB or EFFECTIVE PERCEIVED NOISE in decibels

Question 4

if the runway is ____ enough, depending on load carried, it may be possible to reduce noise by reducing the _______ setting. this will also reduce engine ____

Answer 4

if the runway is LONG enough, depending on load carried, it may be possible to reduce noise by reducing the THROTTLE setting. this will also reduce engine WEAR

Question 5

insulating material can be placed around the noisiest part of the engine, which on a high by-pass is the ___ but can also be extended to insulate the __________ section and _______, too. material will absorb acoustic energy and convert into ____ and then disperse. normally ________ or ________ honeycomb but can be composite

Answer 5

insulating material can be placed around the noisiest part of the engine, which on a high by-pass is the FAN but can also be extended to insulate the COMBUSTION section and TURBINE, too. material will absorb acoustic energy and convert into HEAT and then disperse. normally ALUMINIUM or TITANIUM honeycomb but can be composite

Question 6

another insulating material is air in the form of by-pass duct air. high-bypass engines much ________

Answer 6

another insulating material is air in the form of by-pass duct air. high-bypass engines much QUIETER

Question 7

reducing the velocity of the jet efflux by mixing ____-stream air with ___ stream air to produce a lower _______ efflux, or _________ cold-stream air around hot gas to provide an intermediary boundary velocity reduces noise

Answer 7

reducing the velocity of the jet efflux by mixing COLD-stream air with HOT stream air to produce a lower VELOCITY efflux, or WRAPPING cold-stream air around hot gas to provide an intermediary boundary velocity reduces noise