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Flashcards in Noise and Vibration Deck (21):
0

The most aeromedical significant frequencies for communications are in the ________ to __________ range.

500 to 4,000 Hz range

1

Accordingly, the Occupational Health and Safety Administration has limited permissible exposure of sound for a worker over a career to _______ dB for eight hours a day over a 40 hour work week.

90 dB

2

A helpful noise comparison guide for airmen is provided by the National Institute for Occupational Safety and Health:
Whisper 30 dB
Normal conversation 60 dB
Lawn Mower 90 dB
Chain Saw 110 dB
Ambulance Siren 120 dB
Jet Engine 140 dB

NIOSH permissible exposure time limits:
8 hours 85 dB (5 dB lower than OSHA standard)
4 hours 88 dB
2 hours 91 dB
1 hour 94 dB

85 dB

3

Wax impregnated foam polyurethane ear plugs provide how much noise protection on average?

30-35 dB

4

Hearing is covered under what section of FAA regulations?

14 Code of Federal Regulations Part 67

5

The frequencies most important for human speech are:
a) 20 to 500 Hz
b) 500 to 4,000 Hz
c) 3,000 to 6,000 Hz
d) 6,000 to 20,000 Hz

b) 500 to 4,000 Hz

6

The mechanism of the ear for converting the sound pressure waves from an air to a fluid medium without signficant loss of energy is called impedance matching and this is done through:
a) rapid fatigue of the auditory nerves.
b) movement of the otoliths in the cochlear canals
c) size differential between the eardrum and the footplate of the stapes and the lever action of the ossicles.
d) the property of binaural hearing and that sound waves do not strike the ears at the same intensity.

c) Only 1% of airborne sound enters the liquid medium whereas 99% is reflected away. The middle ear has two arrangements to narrow this potential energy loss. The first is the size differential between the eardrum and the footplate of the stapes. The second is the lever action of the ossicles amplifies the intensity of sound as it traverses the middle ear by 2.5 dB.

7

Noise exposure is commonly thought to be a combination of time and exposure level. What is the criterion noise exposure level which would give a person a daily limiting noise exposure for an 8 hour period with the associated exchange rate according to the US military and US EPA?
a) 84 db for 8 hours with 4 db per doubling
b) 85 db for 8 hours with 3 db per doubling
c) 90 db for 8 hours with 5 db per doubling
d) 78 db for 8 hours with a 6 db per doubling

b) 85 db for 8 hours with 3 db per doubling

8

Loudness is a psychoacoustic phenomenon. When a listener judges a sound to be twice (or half) as loud when compared to another sound, the difference is sound pressure level between the two sounds is approximately ___________.

10 dB

9

Parameters describing an oscillatory motion are:
a) amplitude
b) frequency
c) period
d) acceleration
e) all the above

e) all the above

10

When excited with certain input frequencies, resonances of body parts can occur, ie- the deformation or displacement of the organ is much larger at the resonance frequency than at other frequencies. The body's lowest tolerance to vibration is:

4-8 Hz

11

Many noise control problems require a practical knowledge of the relationship between pressure, intensity, and power. In measuring noise levels in locations that are reverberant, one can expect that the noise levels will be:
a) lower than predicted values
b) higher than predicted values
c) at the predicted values
d) none of the above

b) higher than predicted values

12

The limiting factor for the toleration to vibrations of 2-12 Hz is:
a) Chest pain
b) Dyspnea
c) Tachyarrhythmia
d) abdominal pain

a) Chest pain

13

A simplified model for the representation of a vibratory system is made up of:
a) a mass, a spring, and a shock absorber
b) a mass, a spring, and a damper
c) a mass, a filter, and a damper
d) a mass, a spring, a damper, and a filter

b) a mass, spring, and a damper

14

Whole body vibration occurring in flight concerns primarily those frequencies between:
a) 20-20,000 cycles/second
b) 0.5-200 Hz
c) 0.01-1.0 Hz
d) greater than 100 cycles/second

b) 0.5 -200 Hz

15

The effects of vibration at frequencies of less than 2 Hz include all of the following EXCEPT:
a) motion sickness
b) fatigue
c) inability to maintain control of the aircraft
d) hearing loss
e) structural aircraft damage

d) hearing loss

16

The ordinary sound level meter:
a) gives a direct measurement of loudness
b) cannot accurately measure impulse noise
c) is capable of accurate frequency analysis
d) is the preferred instrument for detailed monitoring and specific analysis of sound content.

b) cannot accurately measure impulse noise

17

Resonance of a system exposed to forced vibration exists when any change, however small, in the frequency of excitation causes ________________.

A decrease in a response of the system.

18

The only specific vibration induced disease with well supported evidence is:
a) whole body vibration syndrome
b) vibration induced back pain
c) White Finger syndrome
d) retinal detachment
e) vibration induced menstrual disorder

c) Vibration Induced White Finger Syndrome.

19

According to the vibration exposure criteria presented in ISO 2631, the seated or standing human exposure to whole body vibration in the VERTICAL direction is most sensitive to vibration frequencies occuring between ___________.

4-8 Hz

20

According to the vibration exposure criteria presented in the ISO 2631 the seated or standing human exposed to whole body vibration in the HORIZONTAL direction (lateral, fore and aft) is most sensitive to vibration frequencies occurring between ___________.

1-2 Hz