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Building Systems > PDX_27_Acoustics Part 2 > Flashcards

PDX_27_Acoustics Part 2 Flashcards

1
Q

PDX_28_Acoustics #3

Velocity of sound (FPS)/Frequency of sound (HZ)=

A

Wavelength (λ)

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2
Q

PDX_28_Acoustics #3

Acoustic power (P)/4πr²=

A

Sound intensity (watts/unit area)*we typically deal with decibels instead

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3
Q

PDX_28_Acoustics #3

Sound intensity (I₁) / (I₂)=Distance from source (r²₂) / (r²₁)

A

Inverse square law

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4
Q

PDX_28_Acoustics #3

10 log (Intensity of sound being measured)/Reference intensity of 1x10⁻¹⁶

A

Sound intensity level (decibel)

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5
Q

PDX_28_Acoustics #3

(Barrier transmission, TL)-10log [(area of barrier wall, S) /(total absorption of receiving room, Ar)]

A

Noise reduction (dB)

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6
Q

PDX_28_Acoustics #3

Three basic qualities of sound:

A

Velocity, frequency, and power

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7
Q

PDX_28_Acoustics #3

This quality depends on the medium in which the sound is traveling and the temperature of that medium

A

Velocity

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8
Q

PDX_28_Acoustics #3

This quality as the number of cycles completed per second, measured in hertz

A

Frequency

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9
Q

PDX_28_Acoustics #3

This quality of acoustical energy, measured in Watts

A

Power

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10
Q

PDX_28_Acoustics #3

Velocity of sound in air:

A

1130 ft./s(A constant)

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11
Q

PDX_28_Acoustics #3

Velocity of sound in wood:

A

11,700 ft./s

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12
Q

PDX_28_Acoustics #3

Velocity of sound in water:

A

4,500 ft./s

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13
Q

PDX_28_Acoustics #3

Velocity of sound in steel:

A

18,000 ft./s

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14
Q

PDX_28_Acoustics #3

The distance between similar points on successive waves or the distant sound travels and one cycle. Measured linear feet.

A

Wavelength

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15
Q

PDX_28_Acoustics #3

Human ear can hear sounds in this range:

A

20 Hz – 20,000 Hz range

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16
Q

PDX_28_Acoustics #3

Most sensitive sound range to the human ear is:

A

125 Hz – 6000 Hz range

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17
Q

PDX_28_Acoustics #3

Speech is composed of sound primarily in this range:

A

100 Hz – 600 Hz

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18
Q

PDX_28_Acoustics #3

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

A

Octave band

19
Q

PDX_28_Acoustics #3

In building acoustics, measurements and analysis is often divided into___ identified by their center frequency

A

Eight octave bands

20
Q

PDX_28_Acoustics #3

Types of sound measurement:The decibel, how intense the sound is

A

Send intensity level (IL)

21
Q

PDX_28_Acoustics #3

Types of sound measurement:Watts/cm², The power at the source

A

Sound power level (PWL)

22
Q

PDX_28_Acoustics #3

Types of sound measurement:The pressure exerted by the sound waves on a surface at a given location, varies with barometric pressure.

A

Sound pressure level (SPL)

23
Q

PDX_28_Acoustics #3

Smallest difference into sounds the human ear can detect is:

A

1 dB

24
Q

PDX_28_Acoustics #3

Each increase of 10 dB the human ear perceives as:

A

10x loudness

25
Q

PDX_28_Acoustics #3

130 dB

A

Decibel level at threshold of pain:

26
Q

PDX_28_Acoustics #3

Typically doubling the distance between the source and the ear reduces levels by:

A

6 dB

27
Q

PDX_28_Acoustics #3

Human years more sensitive to sounds in these frequencies:

A

Middle frequencies

28
Q

PDX_28_Acoustics #3

Walls located between source and here are most effective located:

A

Close to source

29
Q

PDX_28_Acoustics #3

The scale of the most closely represents the response of the human ear is called the:

A

A scaleWhen measurements using to a scaler converted to decimals, the resultant measure is designated dBA

30
Q

PDX_28_Acoustics #3

The difference (in dB) between the sound power incident on a barrier in a source room and the sound power radiated into a receiving room on the opposite side of the barrier

A

Transmission loss (TL)

31
Q

PDX_28_Acoustics #3

The arithmetic difference (in decibels) between the intensity levels in two rooms separated by a barrier of a given transmission loss.

A

Noise reduction (NR)

32
Q

PDX_28_Acoustics #3

Method of rating walls, doors, etc. In terms of their typical or overall resistance to sound transmission.

A

Sounds transmission class (STC)

33
Q

PDX_28_Acoustics #3

Typical STC ratings:STC 25

A

Normal speech can be clearly heard through barrier

34
Q

PDX_28_Acoustics #3

Typical STC ratings:STC 30

A

Lab speech can be heard and understood well, normal speech to be heard, but barely understood.

35
Q

PDX_28_Acoustics #3

Typical STC ratings:STC 35

A

Loud speech can be heard but not understood

36
Q

PDX_28_Acoustics #3

Typical STC ratings:STC 41-45

A

Loud speech can only be faintly heardCan’t hear normal speech at all

37
Q

PDX_28_Acoustics #3

Typical STC ratings:STC 46–50

A

Loud speech is not audibleLoud sounds other than speech can only be faintly heard

38
Q

PDX_28_Acoustics #3

Variables of sound have been consolidated into a set of curbs used and specifying the maximum noise level in a given space under a given set of conditions

A

Noise criteria (NC) curves

39
Q

PDX_28_Acoustics #3

A modification of NC curves that have sound pressure level slower than the NC curves on the low/high-frequency needs of the chart.

A

Preferred noise criteria (PNC)

40
Q

PDX_28_Acoustics #3

The apparent change in frequency or wavelength of a wave it’s perceived by an observer moving relative to the source of the wave

A

Doppler effect

41
Q

PDX_28_Acoustics #3

Used to measure the degree of isolation of impact noises in a structure A ‘tapping machine’ is used

A

Impact isolation class (IIC)

42
Q

PDX_28_Acoustics #3

Mess law is based on the principle that the larger the mass the less it will:

A

Vibrate

43
Q

PDX_28_Acoustics #3

Technique used to hide unwanted sounds by the addition of controlled sounds (a.k.a. pink/white noise)

A

Sound masking

Building Systems (37 decks)

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