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Term 2 Theory Prep > Digital Audio > Flashcards

Digital Audio Flashcards

1
Q

What does PPM stand for?

A

Pulse Position Modulation

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2
Q

DEF: Pulse Position Modulation (PPM)

A

for each number there is a position in time with subdivisions, the subdivision within that time dictates the number being communicated

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3
Q

what does PNM stand for?

A

Pulse Number Modulation

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4
Q

DEF: Pulse Number Modulation (PNM)

A

for each number communicated you have a series of pulses equal to the number similar to morse code: 1 pulse = 1, 6 pulses = 6, 13 = 1 pulse followed by 3 pulses, etc.

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5
Q

what does PWM stand for?

A

Pulse Width Modulation

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6
Q

DEF: Pulse Width Modulation (PWM)

A

the length of the pulse dictates the number being communicated short pulse = small number, longer pulse = bigger number

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7
Q

what does PAM stand for?

A

Pulse Amplitude Modulation

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8
Q

DEF: Pulse Amplitude Modulation (PAM)

A

Amplitude dictates the number being communicated lower amplitude = lower number wasn’t very accurate so they needed to develop a better way

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9
Q

what does PCM stand for?

A

Pulse Code Modulation

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10
Q

DEF: Pulse Code Modulation (PCM)

A

uses binary code range of numbers to be communicated is established, which gives you bit depth. Bit depth is then used to communicate the information on and offs that allow transmission of data (think morse code)

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11
Q

what is the binary system

A

a two digit system (base 2 system) made up of 0 and 1 used to represent a larger amount of information

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12
Q

What is a BIT?

A

A binary digit

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13
Q

What is a byte?

A

8-bit word

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14
Q

what is a nibble?

A

4 bits

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15
Q

Bit depth indicates what in binary code?

A

the word length i.e. 4 bit, 24 bit, etc.

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16
Q

what are the sample rate and bit depth setting used for CD?

A

44.1 kHz, 16-bit

17
Q

DEF: sample rate

A

the number of measurements taken in a second

18
Q

DEF: bit depth

A

the amount of values you can give to each sample taken

19
Q

DEF: quantisation

A

the act of assigning a binary value to the voltage amplitude that is read for each sample in the sample

20
Q

DEF: Nyquist theorem

A

double the highest frequency you wish to accurately reproduce

21
Q

What two factors determine the quality of resolution of a digital signal?

A

bit dept and sample rate

22
Q

How do you calculate the number of bits in the binary word?

A

2^n n = binary word length

23
Q

how does the dynamic range change for each bit added to the binary word length?

A

dynamic range increases by approx 6 dB for each bit added

24
Q

DEF: oversampling

A

a process of sampling your signal at a sampling rate significantly higher than the Nyquist frequency, which improves resolution, reduces noise, and helps to avoid aliasing and distortion in the D/A conversion process

25
Q

DEF: aliasing

A

artifact cause when the frequencies above the nyquist frequency fold back into the sound

26
Q

DEF: anti-aliasing filter

A

very steep low pass filter that cuts off frequencies above the Nyquist frequency

27
Q

When are anti-aliasing filters typically used in the A/D D/A conversion process?

A

typically at the input of the ADC

28
Q

When are reconstruction filters used?

A

typically at the output of the DAC

29
Q

How is aliasing prevented by the anti-aliasing filter

A

the bandwidth of the sampled signal is limited to frequencies below the Nyquist frequency

30
Q

DEF: dither

A

intentionally applied form of noise used to the A/D path to improve the resolution of the conversion process and reduce harmonic distortion so the signal’s low-level resolutions can be more accurately interpreted in the ADC process

31
Q

DEF: quantization (DAC)

A

the resolution (overall quality and distortion characteristics) of an encoded signal compared to the original analog signal at its input

32
Q

DEF: jitter

A

time-base errors cause by varying time delays in the circuit paths from component to component in the signal path. Often adding noise, distortion and potentially blurring the signal image

33
Q

What is a worldclock?

A

A “master” clock used to sync the internal clocks of all digital devices so as to avoid jitter, clicks and pops

34
Q

name the digital audio file types

A

AAC , AC3, AIFF, MP3, FLAC, BWF, Vorbis (Ogg), WAV

35
Q

what types of audio compression are lossy?

A

MP3, Vorbis, AC3, AAC

36
Q

lossless audio compression techniques

A

FLAC, WAV

37
Q

What audio compression techniques are “non-compression”?

A

WAV, AIFF, AU

38
Q

what equation is used to determine the number of rows required to communicate a binary value?

A

Term 2 Theory Prep (11 decks)

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