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CTS-D > Elements of Acoustics > Flashcards

Elements of Acoustics Flashcards

1
Q

____ is how the energy is generated; in other words, the source of the sound.

A. Production
B. Propagation
C. Control
D. Interaction
E. Reception
A

A. Production

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2
Q

____ is the pathway of the energy.

A. Production
B. Propagation
C. Control
D. Interaction
E. Reception
A

B. Propagation

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3
Q

____ is how (sound) energy is generated and subsequently propagated.

A. Production
B. Propagation
C. Control
D. Interaction
E. Reception
A

C. Control

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4
Q

____ is how material responds to the sound energy imposed upon it.

A. Production
B. Propagation
C. Control
D. Interaction
E. Reception
A

D. Interaction

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5
Q

____ is how hearers’ ears and brains will respond to the stimuli placed upon them.

A. Production
B. Propagation
C. Control
D. Interaction
E. Reception
A

E. Reception

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6
Q

_____ is the distance between two corresponding points of two consecutive cycles.

A

Wavelength

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7
Q

The speed of sound in air is ____ft per second.

A

1,130 ft (344 m)

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8
Q

Wavelength formula

A

λ = v/f

where:
• λ is the wavelength measured in feet or meters.
• v is the speed of sound in feet (meters) per second.
• f is the frequency in hertz.

divide the speed of sound by frequency

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9
Q

As frequency increases, the wavelength ____.

A

decreases

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10
Q

The unit for sound power is _____.

A

watts per square meter (W/m2)

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11
Q

_____ is the distance of a particle’s movement from its equilibrium position in a medium as it transmits a sound wave.

A

Particle Displacement

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12
Q

_____ is sound that arrives directly from the source to the listener.

A

Direct sound

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13
Q

____ is sound that arrives to the listener after the direct sound as reflected energy.

A

reflections

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14
Q

____ reflections bounce directly off a surface like light bouncing off a mirror. Like light, the incoming angle (the angle of incidence) will equal the outgoing angle (the angle of reflection).

A

Direct (or specular)

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15
Q

____ is the scattering or random redistribution of a sound wave from a surface. It occurs when surfaces are at least as long as the sound wavelengths but not more than four times as long.

A

Diffusion

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16
Q

For reflecting surfaces to function as diffusers, they must be heavily textured and irregular—the dimensions of irregularities should be _____ to the wavelength of sound.

A

nearly equal

17
Q

A _____ is a series of reflections that continue to bounce back and forth between parallel hard surfaces, such as large walls, ceilings, windows, and floors.

A

flutter echo

18
Q

A ____ is the amount of energy at fixed positions within a room. They significantly affect the perceived low-frequency performance in smaller rooms, such as boardrooms, conference rooms, classrooms, home theaters, music practice rooms, and small studios—really, any relatively small room.

A

mode (or standing wave or room resonance)

19
Q

A _____ occurs when a sound wave travels between two reflecting surfaces, such as two parallel walls.

A

standing wave

20
Q

_____is the sound that persists in a room after the energy that created it is stopped.

A

Reverberation

21
Q

The _____ of a space (Figure 11-8) is said to be the number of seconds it takes for the sound to decay to one-thousandth of its original level, or 60 dB.

A

reverberation time

22
Q

Reverberation time is also referred to as _____.

A

RT 60

23
Q

The _____ takes an average of the four middle test frequencies (250, 500, 1000, and 2000).

A

noise reduction coefficient (NRC)

24
Q

Generally speaking, NRC values smaller than ___ are considered to be reflective, while values greater than ___ are considered to be absorptive.

A

0.20 / 0.40

25
Q

The _____ is a single-number rating that is the average, rounded off to the nearest 0.01, of the sound absorption coefficients of a material for the 12 one-third octave bands from 200 through 2500 Hz.

A

sound absorption average (SAA)

26
Q

Acoustic Mass Law formula

A

TL = 20 * log (m * f ) – 47.2

where:
• TL is the transmission loss in dB.
• m is the mass in kg/m2.
• f is the frequency in Hz.

27
Q

_____rates transmission loss at speech frequencies from 125 to 4000 Hz plotted against a standard contour as the reference.

A

Sound transmission class (STC)

28
Q

STC does not evaluate performance at frequencies below ___ Hz, where music and mechanical equipment noise levels can be high.

A

125

29
Q

Speech Privacy

No privacy. Voices clearly heard between rooms.

A. 0-20 STC
B. 20-40 STC
C. 40-55 STC
D. 55-65 STC

A

A. 0-20 STC

30
Q

Speech Privacy

Some privacy. Voices will be heard.

A. 0-20 STC
B. 20-40 STC
C. 40-55 STC
D. 55-65 STC

A

B. 20-40 STC

31
Q

Speech Privacy

Adequate privacy. Only raised voices will be heard.

A. 0-20 STC
B. 20-40 STC
C. 40-55 STC
D. 55-65 STC

A

C. 40-55 STC

32
Q

Speech Privacy

Complete privacy. Only high level noise will be heard. Note that the term complete may not be adequate for some secure facilities.

A. 0-20 STC
B. 20-40 STC
C. 40-55 STC
D. 55-65 STC

A

D. 55-65 STC

33
Q

____ is a rating used to quantify impact sound absorption. It is an average of the attenuation in decibels that occurs at frequencies ranging from 100 to 3150 Hz.

A

Impact insulation class (IIC)

34
Q

The ____ the IIC rating is, the better insulation from impact noise the material provides.

A

higher

35
Q

Within certain time frames, our ear/brain system processes direct and reflected energy as one sound event, known as the _____.

A

integration process

36
Q

Our brain uses the comparison between direct and reflected sound to determine the direction of the sound’s origin, a psychoacoustic effect called _____.

A

precedence effect

37
Q

First notch frequency formula

A

F = 1 / 2t

where:

  • F is the frequency.
  • t is the time in seconds.
38
Q

_____ is the background noise that originates from all sources other than the desired source.

A

Ambient noise

39
Q

An important unseen effect is an increase in loudness, which occurs when the reflected sound is within what is colloquially called the _____ —about 30 ms for speech and 50 ms for music, depending on the temporal structure of the sound.

A

integration interval

CTS-D (17 decks)

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