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Term 1 Theory Prep > H - Decibels > Flashcards

H - Decibels Flashcards

1
Q

what is a decibel

A

a logarithmic unit used to express the ratio of two values of a physical quantity. it is 1/10th of a bell

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2
Q

what 2 values does a decibel require to have meaning

A

how much louder is one sound compared to another/ how much voltage a signal has compared to another

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3
Q

the dB scale describes the ratio of what 2 quantities

A

power (acoustic or electrical) and pressure (acoustic or electrical)

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4
Q

sound pressure level is…

A

the local pressure deviation from the ambient atmospheric pressure, caused by a sound wave

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5
Q

what is a logarithmic scale

A

a non-linear scale used when there is a large range of quantities

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6
Q

our perception of frequency and loudness is….

A

logarithmic

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7
Q

what is the base 10 logarithm

A

the number that 10 must be raised to the power of, in order to equal the number.

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8
Q

a bel is the log of an…..

A

electrical or acoustic power ratio

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9
Q

what is the dB suffix

A

the dB suffix defines the unit type, also defines the standard reference value.

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10
Q

What are weighting networks?

A

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

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11
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

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12
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

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13
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

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14
Q

what is dBm and its reference level

A

became the standard volume indicator and reference level in the 1940s. odBm = 0.001 watts (1 milliwatt)

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15
Q

what is dbV and its reference level

A

was used for many years for voltage reference. 0dbV = 1 volt RMS.

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16
Q

what is dbv and its reference level

A

the NAB adopted the use of the lower case v to denote the voltage value corrosponding to the power indicated by dBm (if one assumes a 600 ohm circuit). 0dBV = 0.775 Volts

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17
Q

what is dBu and its reference level

A

the dBu replaced the dBv, and is the more appropriate term for output or input voltage. 0dBu = 0.775 volts.

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18
Q

what is the nominal operating level for professional standard equipment….

A

+4dBu

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19
Q

what is the nominal operating level for consumer standard equipment….

A

-10dBV

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20
Q

what is the electric power definition

A

electric power is the rate of energy consumption in an electrical circuit

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21
Q

what is dBFS

A

decibels relative to full scale, used for amplitude levels in digital systems. 0dBFS is assigned to the maximum level,

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22
Q

what does a digital systems dynamic range mean

A

the ratio between the maximum signal level and the noise floor.

23
Q

bit depth means

A

the maximum digital level that can be encoded in a digital system determined by the number of bits

24
Q

what does full scale mean

A

the maximum possible value in the positive direction in a PCM digital system

25
Q

what is digital clipping

A

it is a form of distortion when an amplifier or audio signal is driven beyond its maximum capacity.

26
Q

What is the threshold of pain?

A

approx. 130 dB

27
Q

How loud is normal conversation?

A

Approx 60 dB

28
Q

How much is 0dB in Pa?

A

0.00002 Pa

29
Q

what is sound pressure level measured in?

A

Pascals

30
Q

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

A

+3 dB m

31
Q

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

A

-3 dB m

32
Q

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

A

+6 dB SPL

33
Q

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

A

-6dB SPL

34
Q

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

A

+10 dB m

35
Q

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

A

-10 dB m

36
Q

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

A

+20 dB SPL

37
Q

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

A

-20 dB SPL

38
Q

What is the quantifier for Watts re: decibels?

A

dB m

39
Q

What is the quantifier for pressure re: decibels?

A

dB SPL

40
Q

DEF: Sound Pressure Level (SPL)

A

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

41
Q

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

A

Pascal (Pa)

42
Q

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

A

0 dB

43
Q

What type of scale is dB?

A

logarithmic

44
Q

what does RMS stand for?

A

Root Mean Squared

45
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

46
Q

DEF: phon

A

a unit of loudness measurement for pure tones

47
Q

what does the “m” in dBm stand for?

A

milliwatts

48
Q

what is the equivalent to 0dBm in watts?

A

0.001 watts (1 milliwatt)

49
Q

what is the threshold of human hearing

A

o dbSPL

50
Q

what is o dBSPL in pascals

A

0.00002 pascals

51
Q

what level will result in a perforated ear drum

A

160 dB SPL

52
Q

how many pascals is 160dB SPL

A

2000 Pa

53
Q

in a 16-bit system, what is the maximum possible positive level

A

32767

2 to the power of 16 / 2

54
Q

how many samples do people tend to settle on over the maximum level when audible clipping occurs

A

2 or 3

Term 1 Theory Prep (11 decks)

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