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Building Interior Systems II > Exam 1 > Flashcards

Exam 1 Flashcards

Week 1-4

1
Q

What is a unit of measurement for sound pressure, intensity or power:

A

Decibel

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2
Q

What is the name for a Lisener’s perception of the frequency of a pure tone?

A

Pitch

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3
Q

What is the name for the fraction of an incident sound that bounces off a material?

A

Reflectance

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4
Q

What is the name for the fraction of an incident sound that is turned into heat within a material?

A

Absorption

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5
Q

A 10 dB increase represents a perceived loudness increase of:

A

Twice as much

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6
Q

Reverberation times for small to medium spaces designed to facilitate speech should fall between:

A

0.4 – 0.8 seconds

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7
Q

The physical principle underlying free-field sound propagation is:

A

The Inverse Square Law

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8
Q

The minimum threshold of human hearing occurs at 0 decibels.

True or False ?

A

True

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9
Q

What is reverberation defined as?

A

A persistence of sound in a space after the sound source has stopped

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10
Q

what is sound converted into in the process known as sound absorption?

A

Heat

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11
Q

What does Reverberation Time measure?

A

The time it takes for a sound to drop 60 dB

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12
Q

NRC is a good indication of a material’s ability to absorb sound at all frequencies.

True or False

A

False

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13
Q

A material with a NRC of 0.10 is more absorbent than one rated at 0.75.

True or False

A

False

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14
Q

STC is a single number rating that expresses:

A

The transmission loss of a material or construction assembly

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15
Q

“Flanking” describes the ability of sound to:

A

Find the path of least resistance

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16
Q

There is more diffraction with low frequency sounds than with high.

True or False

A

True

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17
Q

In auditorium spaces, seat upholstery and audience members significantly contribute to the sound absorption of the space.

True or False

A

True

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18
Q

What is the name for a sound that is reflected between parallel surfaces of a space?

A

Flutter Echo

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19
Q

Which of the following is desirable for music performances as it spreads the sound evenly over a wide seating area?

A

Diffusion

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20
Q

An interior designer would like to specify a new porous material for a manufacturing space but it must
absorb sound from a machine that produces low frequency. As a professional she should do which of
the following?

A

Check the material’s absorption coefficient for the particular frequency that the machine emits

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21
Q

What are the three common elements in acoustic systems?

A

Source (made louder or softer) , transmission path (transmit more or less sound), and receiver (condition and ability for the listener to receive sound)

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22
Q

The human ear’s response to pressure fluctuations in the air caused by:

A

Vibrating Objects and Air Turbulence which are both sound sources

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23
Q

What is a wave?

A

A wave is a disturbance or variation that transfers energy from point to point in a medium.

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24
Q

What is frequency?

A

Frequency is the speed of the oscillations, the time taken for one compression / decompression cycle.
Frequency is measured in cycles per second

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25
Q

Sound Waves – Stationary Source

A

Sound energy waves can be pictured radiating in air as a series of concentric rings or spheres growing in size

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26
Q

Sound Waves – Moving Source

A

The wavefronts are produced with the same frequency as before. However, since the source is moving, the center of each new wavefront is now slightly displaced to the right.

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27
Q

How will an observer in front of a moving source hear the source in comparison to an observer behind the source?

A

An observer in front of the source will hear a higher frequency and an observer behind the source will hear a lower frequency

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28
Q

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

A

About 340 m/s or about 750 mph
- an observer in front of the source will detect nothing until the source arrives

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29
Q

How does Sound travel?

A

At a velocity that depends on the elasticity and density of the medium

30
Q

How does sound travel in air, steel, and water?

A

Air: 1130 ft/sec (750 mph) 1 mile every 5 sec
Water: 4800 ft/sec (4000 mph)
Steel: 16,000 ft/sec

31
Q

what is the common pitch of a male and female voice?

A

male: 400 Hz
female: 500 Hz

32
Q

what is an octave?

A

An interval between one pitch and another with
half or double its frequency. Therefore, the ratio of frequencies between two notes, one octave apart is 2:1
for example: 400 Hz - 800 Hz

33
Q

What is Logarithmic Scale?

A

When equal interval sensations between two magnitudes of a quantity are obtained by the same ratio, we say the quantity follows a logarithmic scale

34
Q

What is sound intensity?

A

The physical quantity associated with the loudness of a sound, defined as the amount of sound power falling on (or passing through) a unit area.
Since the unit of power is a Watt:
Sound Intensity = W/m^2

35
Q

what are the thresholds of sound?

A

10-12 W/m2 = 0 dB
(Threshold of
audibility)
10 W/m2 = 120-130 dB
(Threshold of pain)
108 W/m2 = 180-200 dB
(Sounds that kill)

36
Q

what are the parts of the human ear?

A

hammel, anvil, stirrup, eardrum

37
Q

what are the perception of change in sound intensity levels?

A

1- imperceptible
3- just perceptible
5- clearly noticeable
10- substantial change

38
Q

what is sound linked to?

A

the nature of sound is inextricably linked with the nature of the space within which it occurs

39
Q

If sound is coming from the front of you, what might you inaccurately think in regards to sound source location?

A

Listener may locate sound inaccurately as coming from above, below, front, or rear

40
Q

If you hear a sound from the left where would you locate the sound source?

A

Listener easily and accurately locates sound as coming from left

41
Q

If you hear a sound from the right where would you locate the sound source?

A

Listener easily and accurately locates sound as coming from right

42
Q

What is the Haas Effect and Echo?

A

Discovered by Dr. Helmut Haas in 1949,

-The law states that when one sound is followed by another with a delay time of approx. 40 ms or less, (below human’s echo threshold) the two are perceived as a single sound

43
Q

Speech intelligibility of 100% is possible with reverberation times of what seconds?

A

0.4 - 0.5 s ( this is the recommended range)

44
Q

How does reverberation increases and decreases?

A

Reverberation increases with volume and decreases with absorption

45
Q

How do you determines the effectiveness of sound absorbing material?

A

The effectiveness of a sound absorbing material can be expressed by its absorption coefficient.

46
Q

What is the measurement of absorption for 1 sqft of concrete?

A

Sound Absorption: 1%
Reflection 99%
Sabins 0.03
Coefficient 0.03

47
Q

What is the measurement of absorption for 1 sqft of plaster?

A

Sound Absorption: 3%
Reflection 97%
Sabins 0.05
Coefficient 0.05

48
Q

What is the measurement of absorption for 1 sqft of acoustic tile?

A

Sound Absorption: 65%
Reflection 35%
Sabins 0.65
Coefficient 0.65

49
Q

What is Sabin (unit)?

A

a sabin is a unit of sound absorption. May be calculated w/ either imperial or metric units.

50
Q

1 sqft of 100% of absorbing material has a value of how many imperial sabin?

A

1 imperial sabin

51
Q

What is the effect for the situation if the difference in coefficient is <0.10.

A

Little (usually not noticeable)

52
Q

What is the effect for the situation if the difference in coefficient is 0.10 - 0.40.

A

Noticeable

53
Q

What is the effect for the situation if the difference in coefficient is >0.40.

A

Considerable

54
Q

What are the Absorption Strategies?

A
  1. Porous Absorbers
  2. Panel Absorbers
  3. Cavity Absorbers
55
Q

Any wave form can be described by its?

A

Amplitude, Wavelength, Frequency

56
Q

What are Porous Absorbers?

A

A porous absorbing material is a solid that contains cavities, channels or interstices so that sound waves are able to enter through them. It is possible to classify porous materials according to their availability to an external fluid such as air.

57
Q

What are Panel Absorbers?

A

Panel absorbers consists of a flat panel made of wood, metal, gypsum board, or plastic material that is arranged in front of an enclosed air volume.

58
Q

What are Cavity Absorbers?

A

The air in the cavity acts as a cushion for absorbing sound. By building cavity walls, a premise may work as a sound proof zone as a large quantity of external noise gets absorbed within the cavity.

59
Q

What is Pitch?

A

Pitch is the subjective response of human hearing to frequency.

Low frequencies are ‘low notes’
High frequencies are ‘high notes’

60
Q

What are Frequency Bands?

A

Frequency is an important variable in how a sound is transmitted or absorbed, and must
be taken into account in designing the acoustics of a building.

61
Q

What is Resonance?

A

Audible resonance is the emphasis of sound energy at particular frequencies

62
Q

What is Diffraction?

A

Diffraction is the bending or ‘flowing’ of a sound wave around an object or through an opening

63
Q

What is Diffusion?

A

Diffusion is the even scattering of sound reflections in a space.

The effect is to blend the sound patterns in a space with the sensation that sound arrives at the
listener from all directions at equal levels

64
Q

What is an Echo?

A

An echo is the distinct repetition of the original sound and is sufficiently loud to be clearly heard above the general reverberation and background noises in a space

65
Q

What is the purpose of a concave surface?

A

Focuses Sound Waves

66
Q

What is the purpose of Convex surface?

A

Scatters Sound waves

67
Q

What happens to a passage of sound ( of same frequency) passing through different opening size?

A

As the opening size decreases, an increasingly larger percentage of sound passes through the opening by diffraction. `

68
Q

What are some acoustic treatments?

A

Fabric drapery, Hinged Panels, Sliding Facings, and Rotatable Elements

69
Q

What is the purpose of hinged panels?

A

sound absorbing material installed on back of sound reflecting panel can be swung into position to vary conditions from hard to soft.

70
Q

What is the purpose of Sliding Elements?

A

Two panels of perforated material can be used to vary absorption by sliding one panel in front of the other. The holes are lined up for maximum absorption and staggered for maximum reflection.

71
Q

What is the purpose of Rotatable Elements?

A

the object have rotating sides of reflecting, absorbing, and diffusing

Building Interior Systems II (1 decks)

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