PDX_27_Acoustics Part 2

Question 1

PDX_28_Acoustics #3

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

Answer 1

Wavelength (λ)

Question 2

PDX_28_Acoustics #3

Acoustic power (P)/4πr²=

Answer 2

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

Question 3

PDX_28_Acoustics #3

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

Answer 3

Inverse square law

Question 4

PDX_28_Acoustics #3

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

Answer 4

Sound intensity level (decibel)

Question 5

PDX_28_Acoustics #3

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

Answer 5

Noise reduction (dB)

Question 6

PDX_28_Acoustics #3

Three basic qualities of sound:

Answer 6

Velocity, frequency, and power

Question 7

PDX_28_Acoustics #3

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

Answer 7

Velocity

Question 8

PDX_28_Acoustics #3

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

Answer 8

Frequency

Question 9

PDX_28_Acoustics #3

This quality of acoustical energy, measured in Watts

Answer 9

Power

Question 10

PDX_28_Acoustics #3

Velocity of sound in air:

Answer 10

1130 ft./s(A constant)

Question 11

PDX_28_Acoustics #3

Velocity of sound in wood:

Answer 11

11,700 ft./s

Question 12

PDX_28_Acoustics #3

Velocity of sound in water:

Answer 12

4,500 ft./s

Question 13

PDX_28_Acoustics #3

Velocity of sound in steel:

Answer 13

18,000 ft./s

Question 14

PDX_28_Acoustics #3

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

Answer 14

Wavelength

Question 15

PDX_28_Acoustics #3

Human ear can hear sounds in this range:

Answer 15

20 Hz – 20,000 Hz range

Question 16

PDX_28_Acoustics #3

Most sensitive sound range to the human ear is:

Answer 16

125 Hz – 6000 Hz range

Question 17

PDX_28_Acoustics #3

Speech is composed of sound primarily in this range:

Answer 17

100 Hz – 600 Hz

Question 18

PDX_28_Acoustics #3

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

Answer 18

Octave band

Question 19

PDX_28_Acoustics #3

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

Answer 19

Eight octave bands

Question 20

PDX_28_Acoustics #3

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

Answer 20

Send intensity level (IL)

Question 21

PDX_28_Acoustics #3

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

Answer 21

Sound power level (PWL)

Question 22

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.

Answer 22

Sound pressure level (SPL)

Question 23

PDX_28_Acoustics #3

Smallest difference into sounds the human ear can detect is:

Answer 23

1 dB

Question 24

PDX_28_Acoustics #3

Each increase of 10 dB the human ear perceives as:

Answer 24

10x loudness

Question 25

# PDX_28_Acoustics #3 130 dB

Answer 25

Decibel level at threshold of pain:

Question 26

# PDX_28_Acoustics #3 Typically doubling the distance between the source and the ear reduces levels by:

Answer 26

6 dB

Question 27

# PDX_28_Acoustics #3 Human years more sensitive to sounds in these frequencies:

Answer 27

Middle frequencies

Question 28

# PDX_28_Acoustics #3 Walls located between source and here are most effective located:

Answer 28

Close to source

Question 29

# PDX_28_Acoustics #3 The scale of the most closely represents the response of the human ear is called the:

Answer 29

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

Question 30

# 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

Answer 30

Transmission loss (TL)

Question 31

# 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.

Answer 31

Noise reduction (NR)

Question 32

# PDX_28_Acoustics #3 Method of rating walls, doors, etc. In terms of their typical or overall resistance to sound transmission.

Answer 32

Sounds transmission class (STC)

Question 33

# PDX_28_Acoustics #3 Typical STC ratings:STC 25

Answer 33

Normal speech can be clearly heard through barrier

Question 34

# PDX_28_Acoustics #3 Typical STC ratings:STC 30

Answer 34

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

Question 35

# PDX_28_Acoustics #3 Typical STC ratings:STC 35

Answer 35

Loud speech can be heard but not understood

Question 36

# PDX_28_Acoustics #3 Typical STC ratings:STC 41-45

Answer 36

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

Question 37

# PDX_28_Acoustics #3 Typical STC ratings:STC 46–50

Answer 37

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

Question 38

# 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

Answer 38

Noise criteria (NC) curves

Question 39

# 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.

Answer 39

Preferred noise criteria (PNC)

Question 40

# 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

Answer 40

Doppler effect

Question 41

# PDX_28_Acoustics #3 Used to measure the degree of isolation of impact noises in a structure A 'tapping machine' is used

Answer 41

Impact isolation class (IIC)

Question 42

# PDX_28_Acoustics #3 Mess law is based on the principle that the larger the mass the less it will:

Answer 42

Vibrate

Question 43

# PDX_28_Acoustics #3 Technique used to hide unwanted sounds by the addition of controlled sounds (a.k.a. pink/white noise)

Answer 43

Sound masking