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Sound Theory > Sound Theory > Flashcards

Sound Theory Flashcards

1
Q

Hertz is named after who? Why?

A

Named after Heinrich HertzHe was the first person to conclusively prove the existence of electromagnetic waves

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2
Q

What is the generally accepted range of human hearing?

A

20 Hz - 20 kHz

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3
Q

What affects the speed at which sound travels?

A

Temperature and density of the given medium

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4
Q

What is a decibel?

A

1/10th of a Bel

A dimentionless unit used to describe a ratio of either power or pressure; needs two values to have meaning

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5
Q

When a sound is louder, how does it affect the frequencies?

A

As sound gets louder the frequency response becomes more linear—you perceive all frequencies more evenly rather than perceiving some frequencies as being louder than others

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6
Q

What is the threshold of pain?

A

approx. 120 dB

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7
Q

How loud is normal conversation?

A

Approx 60 dB

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8
Q

What is white noise?

A

All frequencies at the same actual volume

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9
Q

What is pink noise?

A

All frequencies as the same perceived volume

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10
Q

DEF: diffusion

A

The scattering of sound waves evenly throughout a given space

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11
Q

DEF: refraction

A

A change in direction of a sound wave caused by the sound wave hitting a medium through which the sound travels differently

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12
Q

DEF: absorption

A

When sound waves are absorbed into a medium and converted from sound energy into heat

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13
Q

DEF: diffraction

A

The bending of waves around an obstacle or spreading out of waves beyond small openings

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14
Q

How do high frequencies react when diffracted?

A

They are highly directional either focusing as they pass through an opening or being blocked by an obstacle

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15
Q

What is the speed of sound at 21° C?

A

343.6 m/s (344 m/s rounded up)

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16
Q

How does density of a medium affect the speed of sound?

A

The more dense the medium, the faster sound travels. sound travels fastest in solids, then liquids, and more slowly in gasses

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17
Q

How does temperature affect the speed of sound?

A

Sound travels faster in warmer temperatures and slower in cooler temperatures

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18
Q

How do you calculate the distance a sound is travelling?

A

d = c x t (Distance = speed x time)

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19
Q

How do you calculate the time a sound will take to travel at a certain distance ?

A

t = d/c (Time = distance / speed)

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20
Q

How do you calculate the speed at which a sound is travelling?

A

c = d/t (Speed = distance / time)

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21
Q

What is sound, technically?

A

Sound is fluctuation in air pressure that uses a medium to propagate, reaches our eardrum, vibrates our eardrums and registers as sound in our brain

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22
Q

What are the two types of waves in which sound can travel?

A

Longitudinal and transverse waves

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23
Q

What two periods make up a single cycle of a sound wave?

A

A period of compression (increased pressure), followed by a period of rarefaction (decrease pressure)

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24
Q

What is a zero crossing?

A

The centre line of zero amplitude in a sine wave that is reflected in DAWS

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25
Q

DEF: reflection

A

Sound bouncing off a surface and returning in the direction from which it arrived

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26
Q

How does sound behave when reflected off a concave object?

A

Sound becomes more focused/stronger

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27
Q

How does sound behave when reflected off a convex surface?

A

It diffuses

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28
Q

How much is 0dB in Pa?

A

0.00002 Pa

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29
Q

If there is a doubling of power (Watts) what is the rule?

A

+3 dB m

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30
Q

If there is a halving of power (Watts), what is the rule?

A

-3 dB m

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31
Q

If there is a doubling in pressure (SPL), what is the rule?

A

+6 dB SPL

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32
Q

If there is a halving in pressure (SPL), what is the rule?

A

-6dB SPL

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33
Q

If there is a tenfold increase in power (Watts), what is the rule?

34
Q

If there is a tenfold decrease in power (Watts), what is the rule?

35
Q

If there is a tenfold increase in pressure (SPL), what is the rule?

A

+20 dB SPL

36
Q

If there is a tenfold increase in pressure (SPL), what is the rule?

A

-20 dB SPL

37
Q

What is the quantifier for Watts re: decibels?

38
Q

What is the quantifier for pressure re: decibels?

39
Q

Formula for determining ratio for power

A

dB m = 10 x log (p1/p2)

40
Q

Formula for determining ratio for sound pressure

A

dB SPL = 20 x log (e1/e2)

41
Q

DEF: Sound Pressure Level (SPL)

A

local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure, caused by a sound wave

42
Q

What is the standard international (SI) unit for sound pressure?

A

Pascal (Pa)

43
Q

If only one value is given when determining dB ratio, what is the assumed other value?

44
Q

What type of scale is dB?

A

logarithmic

45
Q

DEF: Envelope

A

The way a sound’s amplitude changes over time

46
Q

DEF: Attack

A

the beginning of the sound and the way it changes before it reaches its steady-state intensity

47
Q

DEF: Decay

A

the rate at which a sound fades to silence

48
Q

Formula for determining speed of sound at a given temperature?

A

c = 331 + 0.6 x t

49
Q

DEF: Sustain

A

the steady state of a sound at its maximum intensity

50
Q

What is the speed of sound at 0ºC?

51
Q

DEF: amplitude

A

The amount of pressure being exerted on molecules in dB

52
Q

what does RMS stand for?

A

Root Mean Squared

53
Q

DEF: root mean squared (RMS)

A

a calculation of the average of values over a period of time to determine the average perceived loudness

54
Q

What is the formula for calculating the length of a soundwave in meters?

A

λ = c / f

55
Q

How do you determine the added frequencies that occur as a result of the combination and interaction of two sine waves?

A

calculate the sum of both and the difference of both

56
Q

What is the formula for calculating phase shift in degrees?

A

Ø = Δt x 360 x f

measured in miliseconds

57
Q

What is the formula for calculating phase shift in cycles?

A

Ø = Δt x f

58
Q

What is the makeup of a triangle wave?

A

A sine wave plus odd harmonics, increasing in frequency and decreasing in amplitude stacked on top of each other

59
Q

What is the makeup of a square wave?

A

a sine wave with odd harmonics, but has more harmonics than the triangle wave

60
Q

What is the makeup of a sawtooth wave?

A

a sine wave with odd and even harmonics above the fundamental

61
Q

Comparatively, how do pink and white noise sound to us?

A

White noise sounds very bright because of the way our ears perceive sound.

Pink noise sounds darker because there is more low end content

62
Q

What does the fundamental tone determine?

63
Q

How does a triangle wave sound?

A

sounds brighter than the sine wave because it contains higher frequencies as part of the sound rather than just the fundamental

64
Q

How does a square wave sound?

A

brighter still than the triangle because it has more harmonics

65
Q

How does a sawtooth wave sound?

A

brightest of all the basic wave shapes because it has the most harmonics; more nasal

66
Q

Do sine waves start in or out of phase and by how much?

A

Sine waves start in phase

67
Q

Do cosine waves start in or out of phase and by how much?

A

Cosine waves start 90º out of phase

68
Q

DEF: phon

A

a unit of loudness measurement for pure tones

69
Q

DEF: masking

A

when a sound is covered up by another, louder/more harmonically rich sound in the same frequency range

70
Q

Why do sound waves travel faster in warmer temperatures?

A

The air molecules have more energy at a higher temperature and vibrate faster enabling sound waves to travel more quickly

71
Q

What is a longitudinal wave?

A

A wave in which the displacements of a medium are in the direction of or directly opposite to the direction of prolongation of the wave

72
Q

What is a transverse wave?

A

A wave where the displacements of a medium are at a right angle to the direction of propagation of a wave

73
Q

what does the “m” in dBm stand for?

A

milliwatts

74
Q

what is the equivalent to 0dBm in watts?

A

0.001 watts (1 milliwatt)

75
Q

P = V^2 / R

A 
R = resistance in ohms
V= voltage in volts
P= electric power in watts
76
Q

What equation do you use when calculating the value in dBu against a given reference in watts ?

A

pressure

dBu = 20 x log (p1/p2)

77
Q

What equation do you use when calculating the value in dBV against a given reference in volts ?

A

pressure

dBu = 20 x log (p1/p2)

78
Q

What equation do you use when calculating the value in dBm against a given reference in volts ?

A

power

dBm = 10 x log (e1/e2)

79
Q

What are weighting networks?

A

Ways of measuring decibels which account for the Fletcher Munsen curve.

80
Q

A Freq. Weighting (incl. Phon line reference)

A

weighting network designed to reflect the response of human hearing, generally shown in dB(A).
Has the most dramatic frequency response
referenced to the 40 Phon line used between 20-55 dB SPL

81
Q

B Freq. Weighting (incl. Phon line reference)

A

Used to weight things of moderate volume
referenced to the 70 Phon line
used between 55-85 dB SPL

82
Q

C Freq. Weighting (incl. Phon line reference)

A

used for louder volumes, above 80 dB
referenced to the 100 Phon line
used about 85 dB SPL

Sound Theory (4 decks)

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