Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ARE Building Systems > ACOUSTICS > Flashcards

ACOUSTICS Flashcards

0
Q

What do you measure velocity of sound in?

A

Ft/sec

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Symbol for coefficient of absorption

A

Lowercase a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Symbol for wavelength

A

Lowercase w

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Symbol for power

A

Uppercase W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is amplification?

A

Increased intensity of sound by mechanical or electrical means

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is articulation index?

A

A measure of speech intelligibility calculated from the number of words read from a selected list that are understood by an audience.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a low articulation index and what is the desired situation?

A

0.15 or less, for privacy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a high articulation index and what is the desired situation?

A

Above 6.0 is desired for good communication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Attenuation

A

The reduction of sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Decibel - definition and formula

A

10 times the common logarithm of a the ratio to a reference quantity of the same kind, such as power, intensity, or energy density. … Often the unit of sound intensity in this formula:

IL = 10*log(I/Io)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Symbol and measure for sound intensity

A

Capital I… W/cm squared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Symbol for minimum sound intensity audible to the average human ear

A

Io … 10 to the negative 16’s W/cm squared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Symbol and measure for sound intensity level

A

IL measured in dB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Symbol and measure for noise reduction

A

NR …dB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Symbol and measure for acoustic power

A

P … W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Symbol and measure for area of barrier or component between rooms

A

S … Feet squared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Symbol and measure for coefficient of transmission

A

t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Symbol and measure for total acoustical absorption

A

A … Sabins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

dBA

A

The unit of sound intensity measurement that is weighted to account for the response of the human ear to various frequencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Frequency

A

The number of pressure fluctuations recycles occurring in one second, expressed in hertz (Hz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Hertz

A

The unit of frequency; one cycle per second equals one hertz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Impact insulation class (IIC)

A

A single number rating of a floor-ceilings impact sound transmission performance at various frequencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Intensity

A

The amount of sound energy per second across a unit area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Intensity level

A

10 times the common logarithm of the ratio of a sound intensity to a reference intensity… The formula for decibel describes this

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Noise

A

Any unwanted sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Noise criteria (NC)

A

A set of single number ratings of acceptable background noise corresponding to a set of curves specifying sound pressure levels across octave bands. Noise criteria curves can be used to specify continuous background noise, achieve the sound isolation, and evaluate existing noise situations.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Noise insulation class (NIC)

A

A single number rating of noise reduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Noise reduction

A

The arithmetic difference, in decibels, between the intensity levels in two rooms separated by a barrier of a given transmission loss. Noise reduction is dependent on the transition loss of the barrier, the area of the barrier, and the absorption of the surfaces of the receiving room.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Noise reduction coefficient (NRC)

A

The average sound absorption coefficient to the nearest 0.05, measured at the four one third octave band center frequencies of 250, 500, 1000, and 2000 Hz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Octave band

A

A range of frequencies in which the upper frequency is twice that of the lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Phon

A

A unit of loudness level of a sound equal to the sound pressure level of a 1000 Hz tone judged to be as loud

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Reverberation

A

The persistence of a sound in a room after the source has stopped producing the sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Reverberation time

A

The time it takes the sound level to decrease 60 dB after the source has stopped producing the sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Sabin

A

The unit of absorption; theoretically, one square foot of surface having an absorption coefficient of 1.00

34
Q

Sabin formula

A

The formula that relates reverberation time to a room’s volume and total acoustical absorption.

T = 0.05 (V / A)

T is reverberation time
V is room volume
A is total acoustical absorption

35
Q

Sound absorption coefficient

A

The ratio of the sound intensity absorbed by material to the total intensity reaching the material. Theoretically, 1.00 is the maximum possible value of the sound absorption coefficient.

36
Q

Sound power

A

The total sound energy radiated by a source per second, in watts

37
Q

Sound transmission class (STC)

A

A single number average over several frequency bands of a barrier’s ability to reduce sound. The higher the STC rating, the better the barriers ability to control found a transmission.

38
Q

Transmission loss TL

A

The difference, in decibels, between the sound power incident on the barrier and a source room and the sound power radiated into a receiving room on the opposite side of the barrier. The transmission lost varies with the frequency being tested.

39
Q

What are sound’s three basic qualities?

A

Frequency, velocity, and power.

40
Q

What is the velocity of sound in air at sea level?

A

1130 ft./s

41
Q

What is frequency

A

The number of cycles completed per second, measured in hertz.

42
Q

What is the formula relating frequency and velocity?

A

F = C / W

43
Q

Power, in acoustics, is…

A

The quality of acoustical energy is measured in watts.

44
Q

What is the formula for sound intensity?

A

I = P / 4πr²

45
Q

What is the inverse square law?

A

Sounds intensity is inversely proportional to the square of the distance to its source

46
Q

Range of human hearing in decibels

A

0 dB is the threshold of hearing

… 130 dB is the threshold of pain

47
Q

To compute the combined decibel level of multiple sources of sound producing identical decibel sound intensities use the formula:

A

Total IL = IL (of source) + 10log(#of sources)*33.8

48
Q

Rules of thumb for combo sound intensity levels of two sounds…

(Hint: combined decibels)

A

When difference is.. 0-1dB add 3dB
When difference is.. 2-3dB add 2dB
When difference is.. 4-8dB add 1dB
When difference is.. 9dB or more add 0dB

49
Q

Name some common subjective changes in decibel with their effect

A

1 dB - almost imperceptible
5 dB - noticeable
10 dB - twice/half as loud
20 dB - 4 times/one fourth as loud

50
Q

Transmission of sound is primarily retarded by 1.) most important thing 2.) second thing

A

1.) mass of the barrier, 2.) stiffness

51
Q

What is the formula for noise reduction?

A

NR = TL + 10log(A/S)

NR is noise reduction
TL is transmission loss
A is total acoustical absorption of receiving room
S is area of barrier/component bt rooms

52
Q

If you know the value of transmission loss for individual materials, what is the formula for calculating coefficient of transmission?

A

t = 10 to the negative -(TL/10)

53
Q

A conference room and an office I separated by a common wall 13 feet long and 9 feet high with an STC rating of 54. The total absorption of the office has been calculated to be 220 Sabins. What is the total noise reduction from the conference room to the office?

A

57 dB

54
Q

What is the combines transmission loss of a wall 9 feet high and 15 feet long with the 3-ft by 7-ft door in it? Assume the transmission loss of the wall is 54 dB and at the door, with full perimeter seals, is 29 dB.

A

Total wall area = 135
Total door area = 21
Total partition area = 114

t = 10 to the negative -(TL/10)

t of partition = 10 to the -5.4
t of door = 10 to the -2.9

TL = 10log(total area/sum of coefficient of transmission times area of component)

TL = 10log(135/((10 to the -5.4)(114) + (10 to the -2.9)(21)))

= 10log5012
= 37 dB

55
Q

What are some representative noise criteria for different spaces?

A

Concert halls, opera houses, recording studios… 15 to 20 dB

Bedrooms, apartments, hospitals… 20 to 35 dB

Private offices, small conference rooms… 30 to 35 dB

Large offices, retail stores, restaurants… 35 to 40 dB

Lobbyists, drafting rooms, laboratory work spaces… 40 to 45 dB

Kitchens, computer rooms, light maintenance shops… 45 to 55 dB

56
Q

What is the difference between NC and PNC?

A

The difference between noise criteria and preferred noise criteria: it takes into account background noise containing low-frequency and high-frequency sounds, making the sound pressure levels lower than the NC curves on the chart

57
Q

In general, transmission loss through a barrier tends to _____ with the frequency of sound.

A

Increase

58
Q

A wall with .1% open area from cracks, holes, etc., will have a maximum transition loss of _____… A wall with 1% open area will have a maximum transmission loss of about _____…

A

30 dB… 20 dB…

59
Q

A hairline crack will decrease a partitions transmission lost by about _____. A 1 in.² opening in at 100 square-foot Gypsum board partition can transmit _____.

A

6 dB… As much sound of the entire partition…

60
Q

Some affects of barrier STC unhearing effect on hearing are…

A

25 STC… Normal speech can clearly be heard through barrier.

30 STC… Loud speech can be heard and understood fairly well; normal speech can be heard but barely understood.

35 STC… Loud speech is not intelligible but can be heard.

42 to 45 STC loud speech can only be faintly heard; normal speech cannot be heard.

46 to 50 STC… Loud speech is not audible; loud sounds of other than speech can only be heard faintly, if at all.

61
Q

Sound intensity level decreases about _____ for each doubling of distance from the source in free space.

A

6 dB

62
Q

Generally, a material with the color efficient below blank is considered reflective, and one with the coefficient above blank is considered sound absorbing.

A

0.2

63
Q

Express any formula how the total absorption of a material is dependent on its coefficient of absorption and the area of the material.

A

A = Sa

64
Q

What is the formula but describes an increase of sound absorption within a space. What is the formula for the noise reduction that happens once you increase the sound of sorption?

A

NR = 10log(A_1/A_2)

65
Q

A room 15’ x 20’ with 9 foot ceiling has a carpeted floor with 44 ounce carpet on pad (a = 0.40), gypsum board walls, and a gypsum board feeling (a = 0.05. What would be the noise reduction achieved by directly attaching acoustical tile with a given NRC of 0.70 to the ceiling?

A

3.4 dB

66
Q

The average absorption coefficient of a room should be at least what? But not above what (partly because of economical justification)?

A

0.20 dB… 0.50 dB…

67
Q

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

A

3

68
Q

Each doubling of the absorption in the room reduces reverberation time by _____.

A

One half

69
Q

Although absorptive materials can be placed anywhere, what is the best place for sound absorption in a large room? And what is the best place for sound absorption in the small room?

A

For large rooms… The ceiling. For small rooms… The walls.

70
Q

Reverberation time is…

A

… The time it takes the sound level to decrease 60 dB after the source has stopped producing the sound.

71
Q

What is the formula for reverberation time?

A

T = 0.05(V/A)

V is room volume
A is total acoustical absorption

72
Q

In general a shorter reverberation time is best for what size space? And a longer reverberation time is best for what size space?

A

Shorter times for smaller spaces, longer times for larger spaces.

73
Q

Name some recommended reverberation times.

A

Auditoriums speech and music… 1.5 to 1.8 seconds

Broadcast studios, speech only… 0.4 -0.6 seconds

Churches… 1.4-3.4 seconds

Elementary classrooms… 0.6-0.8 seconds

Lecture/conference room… 0.9 to 1.1 seconds

Movie theaters… 0.8 to 1.2 seconds offices, small rooms for speech… 0.3 to 0.6 seconds

Opera house… 1.5 to 1.8 seconds

Symphony concert halls… 1.6 to 2.1 seconds

Theaters, small dramatic… 0.9 to 1.4 seconds

74
Q

What do helmholtz resonators do?

A

They absorb low-frequency sound while reflecting mid and high frequency sound

75
Q

What is another name for the Helmholtz resonator?

A

A cavity resonator… Panel resonators also do the trick

76
Q

What is the difference between articulation class and the articulation index?

A

The articulation class gives a rating of system component performance and does not account for masking sound. The articulation Index measures the performance of all the elements of a particular configuration working together.

77
Q

PAI rating ranges from 0.00 to1.00 which is privacy and which is absolutely no privacy?

A

0.0 is complete privacy and 1.0 is where all individual spoken words can be understood. Confidential privacy is at or below 0.05. Normal speech privacy is between 0.05 and 0.20. Above 0.20 AI speech becomes readily understood. There is no privacy above 0.30.

78
Q

What is the signal-to-noise ratio?

A

The balance between speech sound and background noise

79
Q

What is impact noise? What quantifies it? A higher number means what?

A

Impacts noise is the sound resulting from direct contact of an object with a sound barrier, usually a floor and ceiling assembly. It is quantified by the impact insulation class (IIC) number, a single number rating of a floor ceiling impact on sound performance. A higher number means less sound interruption.

80
Q

What is mechanical noise? What are a few good ways to control it?

A

Similar to impacts noise, mechanical noise occurs when a vibrating device is in continuous direct contact with the structure.

  1. Mount it on springs or pads.
  2. Connect ducts pipes and equipment with flexible connectors
  3. Noise producing equipment should be located away from quiet spaces that’s pretty obvious
81
Q

In sound and acoustics what is the difference between reflection, diffusion, and diffraction?

A

Reflection is the return of soundwaves from a surface. If the surface is greater or equal to four times the wavelength of the sound striking it, the angle of incidence will equal the angle of reflection.

Diffusion is the random distribution of sound from a surface. It occurs when the surface to mention equals the wavelength of the sound of striking out.

Diffraction is the bending of sound waves around an object or through an opening. Diffraction explains why sounds can be heard around corners.

82
Q

The higher the frequency in hertz the _____ the wavelength.

A

Smaller

83
Q

Lighting in watts is to illuminance on a surface as sound power (watts, dB) is to ____ _____.

A

Sound pressure (dB)

ARE Building Systems (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions