Physics of Sound

Question 1

sensation that results from the stimulation of the auditory mechanism by pressure variations in any “elastic” medium

Answer 1

sound

Question 2

unwanted sound

Answer 2

noise

Question 3

requirements for sound

Answer 3

1st- sender
2nd- medium
3rd- receiver

Question 4

source of vibration and source of energy

Answer 4

sender

Question 5

carries the pressure change

Answer 5

medium

Question 6

auditory mechanism to receiver and interpret the signal

Answer 6

receiver

Question 7

causes alternative pressure changes in the air molecules

Answer 7

vibration

Question 8

molecules of the medium forced together causing high pressure

Answer 8

compression

Question 9

molecules of the medium separate causing low pressure

Answer 9

rarefaction

Question 10

a series of compression + rarefactions

Answer 10

sound wave

Question 11

what does speed depend on

Answer 11

depends on the medium, the denser the medium, the faster sound travels

Question 12

1,100 feet per second

Answer 12

air

Question 13

4,500 feet per second

Answer 13

water

Question 14

15,000 feet per second

Answer 14

steel

Question 15

graphical representation of the compressions and rarefactions

Answer 15

sine wave

Question 16

horizontal axis

Answer 16

time

Question 17

vertical axis

Answer 17

molecular vibrations

Question 18

frequency is also known as

Answer 18

pitch

Question 19

sound frequency is quantified in terms of

Answer 19

hertz (Hz)

Question 20

human ear is sensitive to frequencies as low as ___Hz and as high as ___Hz

Answer 20

20
20,000

Question 21

speech hearing range

Answer 21

250 Hz - 4000 Hz

Question 22

consonant sounds

Answer 22

high frequencies

Question 23

vowel sounds

Answer 23

low frequencies

Question 24

human ear is MOST sensitive to sounds in the range between ___Hz and ___Hz

Answer 24

1000
4000

Question 25

human ear is LEAST sensitive in

Answer 25

low frequency range

Question 26

what determines intensity or loudness of a sound

Answer 26

pressure or energy exerted at the source of the sound

Question 27

human ear's perception of amplitude

Answer 27

loudness

Question 28

intensity is expressed in

Answer 28

decibels (dB)

Question 29

range intensity range for human ears

Answer 29

0-140 dB

Question 30

represents the average we can hear

Answer 30

0 dB

Question 31

where serious and immediate damage can occur

Answer 31

140 dB

Question 32

background noise begins to interfere with communication

Answer 32

50 dB

Question 33

level of average speaking voice

Answer 33

60 dB

Question 34

hazardous continuous noise

Answer 34

80 dB

Question 35

hazardous impact noise

Answer 35

140 dB

Question 36

possible tissue damage

Answer 36

170-180 dB

Question 37

possible death

Answer 37

180+ dB

Question 38

if you need to shout to be understood from 3ft away, you are in a potentially hazardous noise environment

Answer 38

three foot rule

Question 39

last longer than one second

Answer 39

continuous noise

Question 40

large differences in sound level occur during the day, with periodic interruptions of relative quiet periods

Answer 40

intermittent noise

Question 41

noise levels that vary in intensity with no significant quiet periods

Answer 41

varying noise

Question 42

very short burst of noise lasting less than one second

Answer 42

impulse noise

Question 43

noises are slightly longer in duration than impulse noises

Answer 43

impact

Question 44

combination of sound waves with a mix of frequencies, with varying intensities

Answer 44

complex tones

Question 45

simplest form of sound and represents one frequency

Answer 45

pure tone

Question 46

microphone to measure sound pressure level (SPL)

Answer 46

sound level meter (SLM)

Question 47

is the amount of sounder energy in the atmosphere

Answer 47

sound pressure level (SPL)

Question 48

the decibel scale is

Answer 48

logarithmic

Question 49

scale used by BE mimicking of the human ear

Answer 49

dBA SPL A scale

Question 50

captures more of the low frequency sounds and slightly more of the high frequency sounds than the A-weighting filter

Answer 50

dBC SPL C scale

Question 51

very loud, fast sounds (impulse noise)

Answer 51

dBP SPL P scale

Question 52

hearing test derived by testing a large group of young, normal hearing people *comparing frequencies over time*

Answer 52

HTL scale

Question 53

when a noise source is doubled the noise level will

Answer 53

increase by 3 dB example: two machines running at 90dB, overall sound level is 93dB

Question 54

doubling the distance from a sound source the intensity of the exposure will *inverse square law*

Answer 54

decrease by 6dB

Question 55

when ___ are used, high frequency sounds are attenuated more than low frequencies

Answer 55

barriers

Question 56

amount of time a worker is exposed to hazardous noise over the work day (8-hr day)

Answer 56

time-weighted average (TWA)

Question 57

percentage of an allowable noise exposure the worker experiences through the work day.

Answer 57

noise dose

Question 58

noise dose takes into account two factors:

Answer 58

permissible exposure limit (PEL) exchange rate

Question 59

8 hour time-weighted average exposure at which point 100% noise dose is reached

Answer 59

permissible exposure limit (PEL)

Question 60

OSHA and most U.S. government regulations use ___dBA as the PEL standard

Answer 60

90

Question 61

DoD sets the maximum PEL at ___dBA

Answer 61

85

Question 62

the amount of decibel increase/decrease in the TWA noise exposure causes the noise dose to double (or cut in half)

Answer 62

decibel exchange rate

Question 63

when the steady sound level is increased, what happens to the duration

Answer 63

cuts in half examples: 85 dBA increased to 88dBA the duration goes from 8 hrs to 4 hrs