Chapter 14 - Acoustics

Question 1

Sound has three basic qualities

Answer 1

velocity, frequency, and power

Question 2

velocity

Answer 2

depends on medium in which the sound is traveling
temperature of the medium

Question 3

frequency

Answer 3

number o cycles completed per second

Question 4

frequency is measured in

Answer 4

Hertz (hz)

Question 5

1 hz equals

Answer 5

1 cycle per second

Question 6

high-pitched sounds have ____ frequencies| bass notes have ______ frequencies

Answer 6

higher| lower

Question 7

power (in acoustics)

Answer 7

quality of acoustic energy

Question 8

power (in acoustics ) is measured in

Answer 8

watts

Question 9

the ______ (unit) is used in acoustic descriptions and calculations

Answer 9

decibel

Question 10

the decibel relates actual ___ _____ to ___

Answer 10

actual sound intensity to the way humans experience sound

Question 11

__ db is the threshold of human hearing| __ __ __ db is the threshold of pain

Answer 11

0 dB| 130 dB

Question 12

Changes in intensity level / change in apparent loudness
1 db

Answer 12

almost imperceptible

Question 13

Changes in intensity level / change in apparent loudness
5 db

Answer 13

clearly noticeable

Question 14

Changes in intensity level / change in apparent loudness
10 db

Answer 14

twice or half as loud

Question 15

Changes in intensity level / change in apparent loudness
18 db

Answer 15

very much louder or quieter

Question 16

Changes in intensity level / change in apparent loudness
20 db

Answer 16

four times or one-fourth as loud

Question 17

a healthy young person can hear the range of about ____-__0,000 Hz

Answer 17

20 - 20,000

Question 18

Human are most sensitive to the Hz range of

Answer 18

3,000 to 4,000

Question 19

There are two basic problems in controlling noise

Answer 19

1. preventing or minimizing the transmission of sound from one space to another
2. reducing the noise within a space

Question 20

Transmission of sound is primarily retarded by ________. what is also important?

Answer 20

the mass of the partition
stiffness, or rigidity, of the partition

Question 21

there are two important concepts in noise reduction

Answer 21

1. transmission loss
2. actual noise reduction between two spaces

Question 22

____ takes into account only the loss through the partition

Answer 22

transmission loss

Question 23

____ is dependent not only on transmission loss but also on the area of the partition separating the two spaces and the absorption of the surfaces in the quiet room

Answer 23

noise reduction

Question 24

how can noise reduction be improved?

Answer 24

1. increasing the transmission loss of the partition
2. by increasing the absorption in the “quiet” room
3. by decreasing the area of the common wall between the rooms
4. some combo the above

Question 25

To simplify the selection of wall construction and other building components, a single-number rating called the _____ is often used to rate the transmission loss of construction.

Answer 25

sound transmission class (STC)

Question 26

the higher the STC, the _______

Answer 26

better the barrier is in stopping sound

Question 27

25 STC =

Answer 27

normal speech can be heard clearly through barrier

Question 28

30 STC =

Answer 28

lounge speech can be heard and understood| normal speech can be heard by not understood

Question 29

35 STC =

Answer 29

loud speech is not intelligible

Question 30

42-45 STC =

Answer 30

loud speech can only be faintly heard

Question 31

46-50 STC =

Answer 31

loud speech not audible; sound sounds other than speech can only be heard faintly

Question 32

low STC to high STC

Answer 32

25-50

Question 33

1. control unwanted sound reflections (noise) 2. improve speech privacy 3. decrease or increase reverberation

Answer 33

sound absorption is used to do 3 things:

Question 34

the absorption of a material is defined by the coefficient of ____________. This ratio is

Answer 34

absorption ratio of sound intensity absorbed by the material to the total intensity reaching the material

Question 35

coefficient below ____ is considered reflective coefficient above ____ is considered absorbing

Answer 35

.2 .2

Question 36

the coefficient of absorption, for convenience, is translated into a single number. This coefficient is referred to as _______.

Answer 36

noise reduction coefficient (NRC)

Question 37

vinyl tile on concrete NRC| 5/8" suspended acoustic tile NRC

Answer 37

.05| .90

Question 38

Each doubling of the amount of absorption in a room results in a noise reduction of only _____

Answer 38

3 dB--hardly noticeable

Question 39

To make any difference in the noise reduction within a space, the total absorption must be increased by at least _______

Answer 39

three times to change the reduction by 5 dB, which is noticeable

Question 40

Although absorptive materials can be placed anywhere, ______ treatment for sound absorption is more effective in large rooms, while _____ treatment is more effective in small rooms.

Answer 40

ceiling wall

Question 41

__________ is the prolongation of sound as it repeatedly bounces off hard surfaces.

Answer 41

reverberation

Question 42

technically, reverberation time is the time it takes the sound level to _________

Answer 42

decrease 60 dB after the source has stopped producing the sound

Question 43

three primary ways sound can be ___________ within a space: 1. by reducing the level of loudness of the sound voice 2. by modifying the absorption in the space 3. by introducing nonintrusive background sound to mask the unwanted sound

Answer 43

controlled

Question 44

Walls and floors are generally rated with their ______ values

Answer 44

STC

Question 45

The higher the STC the _____.

Answer 45

better the barrier is at reducing transmitted sound

Question 46

What type of glass in a door provides better STC?

Answer 46

laminated glass

Question 47

_____, or sound resulting from direct contact of an object with a sound barrier, can occur on any surface, but it generally occurs on a floor and ceiling assembly

Answer 47

impact noise

Question 48

What is one of the most important ceiling ratings for sound?

Answer 48

NRC (noise reduction coefficient)

Question 49

Absorptive ceiling tiles normally have an NRC range of ___ to _____

Answer 49

.65-.90

Question 50

What is a rating similar to the NRC which is often used for ceiling tiles?

Answer 50

SRA speech range absorption singe number rating. range more closely represents the frequencies of speech and may be a better rating to use in evaluating and selecting ceiling tiles

Question 51

third rating method for ceiling tiles is _____

Answer 51

CAC ceiling attenuation class

Question 52

What is CAC?

Answer 52

single-number measure of the transmission loss through ceiling tiles between two closed rooms where there is no wall or other barrier above the suspended ceiling