ENVI ENG

Question 1

is any undesirable or unwanted sound.

Answer 1

Noise

Question 2

The first-generation jet aircraft in the _____ led to a rapid expansion in commercial aviation and their engines created significant noise.

Answer 2

1950s

Question 3

In the 1970s, the U.S. ________________ introduced the first noise certification standards
and the ________________ promoted similar standards
globally (Smith, 1989).

Answer 3

Federal Aviation Administration (FAA) ; International Civil Aviation Organization (ICAO)

Question 4

Chapter 2 of ICAO’s “Environmental Protection/ Annex 16 to the Convention on International Civil Aviation” (ICAO, 2008a) defined ____________
for aircraft certified before October 6, 1977 (with some exemptions);

Answer 4

noise standards

Question 5

Sound level is measured in _______

Answer 5

decibels

Question 6

Two General Sources of noise from aircraft

Answer 6

Engines and the Airframe

Question 7

Aircraft generate noise whenever there is_____________________________.

Answer 7

high-speed or turbulent airflow and/or high-speed mechanical movement and rotation

Question 8

Airframe noise is caused by the __________________________________.

Answer 8

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

Question 9

Engine noise tends to dominate on the ground, especially during _________ when
the engines are at very high thrust level, on _______ when using thrust reversers and
when taxiing at low speed.

Answer 9

takeoff ; landing

Question 10

Another source of aircraft noise besides the engine and airframe

Answer 10

Sonic Boom

Question 11

sonic boom created by aircraft flying at ___________ which can be very
disruptive to activities on the ground.

Answer 11

supersonic speeds

Question 12

The increasingly stringent _______________ have spurred the development of low-noise technologies for new aircraft.

Answer 12

noise certification standards

Question 13

Most reductions in aircraft noise have
been achieved through improvements in _________

Answer 13

engine technology

Question 14

the ratio between the amount of air drawn in by the fan that bypasses the engine core relative
to that passing through the core.

Answer 14

Bypass Ratio

Question 15

Bypass Ratio of Large modem turbofan

Answer 15

10:1

Question 16

Sound Energy radiated by such sources is
transmitted through the air in sound waves which are tiny pressure fluctuations just
above and below atmospheric pressure.

These pressure fluctuations, called _______ , impinge on the ear, creating audible sound.

Answer 16

sound pressures

Question 17

root-mean-square (RMS) value that is the square root of the average squared pressure fluctuation over some brief period of time

Answer 17

Sound Pressures

Question 18

The loudest sounds people can hear without pain have about __________ the RMS sound pressure as the faintest sounds people can hear.

Answer 18

1 million times

Question 19

Equally remarkable
is the way the auditory system perceives _________ in loudness.

Answer 19

changes

Question 20

The smallest difference in RMS sound
pressure the human auditory system can detect is about ________.

Answer 20

10 percent

Question 21

____________, is well suited for quantifying
sound in a manner which relates to human perception.

Answer 21

a logarithmic, or decibel scale

Question 22

In its logarithmic form, RMS
sound pressure is called the _________

Answer 22

RMS sound pressure level (SPL).

Question 23

is the logarithm of the ratio of two squared pressures, the numerator containing the
pressure of the sound source of interest and the denominator containing a reference
pressure

Answer 23

Sound Pressure Level

Question 24

The unit of sound pressure level

Answer 24

decibels

Question 25

Another important attribute of sound is its ___________.

Answer 25

frequency, or pitch

Question 26

unit of frequency

Answer 26

hertz

Question 27

this is the number of times per second the sound pressure oscillates back and forth
about atmospheric pressure

Answer 27

Pure tone

Question 28

The normal frequency range of hearing for a young adult extends from a low of
__________________.

Answer 28

16 Hz to a high of about 16,000 Hz