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NCIDQ IDPX > Chapter 14 - Acoustics > Flashcards

Chapter 14 - Acoustics Flashcards

1
Q

Sound has three basic qualities

A

velocity, frequency, and power

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2
Q

velocity

A

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

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3
Q

frequency

A

number o cycles completed per second

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4
Q

frequency is measured in

A

Hertz (hz)

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5
Q

1 hz equals

A

1 cycle per second

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6
Q

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

A

higher| lower

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7
Q

power (in acoustics)

A

quality of acoustic energy

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8
Q

power (in acoustics ) is measured in

A

watts

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9
Q

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

A

decibel

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10
Q

the decibel relates actual ___ _____ to ___

A

actual sound intensity to the way humans experience sound

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11
Q

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

A

0 dB| 130 dB

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12
Q

Changes in intensity level / change in apparent loudness
1 db

A

almost imperceptible

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13
Q

Changes in intensity level / change in apparent loudness
5 db

A

clearly noticeable

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14
Q

Changes in intensity level / change in apparent loudness
10 db

A

twice or half as loud

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15
Q

Changes in intensity level / change in apparent loudness
18 db

A

very much louder or quieter

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16
Q

Changes in intensity level / change in apparent loudness
20 db

A

four times or one-fourth as loud

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17
Q

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

A

20 - 20,000

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18
Q

Human are most sensitive to the Hz range of

A

3,000 to 4,000

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19
Q

There are two basic problems in controlling noise

A
  1. preventing or minimizing the transmission of sound from one space to another
  2. reducing the noise within a space
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20
Q

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

A

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

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21
Q

there are two important concepts in noise reduction

A
  1. transmission loss
  2. actual noise reduction between two spaces
22
Q

____ takes into account only the loss through the partition

A

transmission loss

23
Q

____ 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

A

noise reduction

24
Q

how can noise reduction be improved?

A
  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
25
Q

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.

A

sound transmission class (STC)

26
Q

the higher the STC, the _______

A

better the barrier is in stopping sound

27
Q

25 STC =

A

normal speech can be heard clearly through barrier

28
Q

30 STC =

A

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

29
Q

35 STC =

A

loud speech is not intelligible

30
Q

42-45 STC =

A

loud speech can only be faintly heard

31
Q

46-50 STC =

A

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

32
Q

low STC to high STC

A

25-50

33
Q
  1. control unwanted sound reflections (noise)
  2. improve speech privacy
  3. decrease or increase reverberation
A

sound absorption is used to do 3 things:

34
Q

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

A

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

35
Q

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

A

.2
.2

36
Q

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

A

noise reduction coefficient (NRC)

37
Q

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

A

.05| .90

38
Q

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

A

3 dB–hardly noticeable

39
Q

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

A

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

40
Q

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.

A

ceiling
wall

41
Q

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

A

reverberation

42
Q

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

A

decrease 60 dB after the source has stopped producing the sound

43
Q

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
A

controlled

44
Q

Walls and floors are generally rated with their ______ values

A

STC

45
Q

The higher the STC the _____.

A

better the barrier is at reducing transmitted sound

46
Q

What type of glass in a door provides better STC?

A

laminated glass

47
Q

_____, 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

A

impact noise

48
Q

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

A

NRC (noise reduction coefficient)

49
Q

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

A

.65-.90

50
Q

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

A

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

51
Q

third rating method for ceiling tiles is _____

A

CAC ceiling attenuation class

52
Q

What is CAC?

A

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

NCIDQ IDPX (42 decks)

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