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Digital Audio Flashcards

(94 cards)

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1
Q

A/D and D/A converters, and where

A

Small piece of circuitry inside interfaces, consoles, cell phones, computers, headsets, MP3 players, CD players, DVD players, BluRay players, etc

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2
Q

A/D converters

A

Takes AC voltage and converts into Binary Code

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3
Q

D/A converters

A

Take Binary Code and converts into AC voltage

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4
Q

The Clock

A

Uses crystals (commonly quartz) to maintain a precise frequency, which regulates the movement of a timing device (watches, CONVERTERS)

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5
Q

Why is the Clock important in a converter?

A

It is responsible for the accuracy and timing of the converter when converting A/D or D/A

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6
Q

PCM

A

Pulse Code Modulation

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7
Q

PCM’s two basic properties that determine quality of recorded audio

A
  1. Sample rate

2. Bit depth

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8
Q

Sample rate

A

Determines frequency response

How many samples per second per track

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9
Q

Bit depth

A

Determines dynamic range and resolution (volume)
Deals with amount of information happening
Amount of bits stored for every sample take

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10
Q

Samples

A

Samples are snapshots of information throughout bit depth (volume/level) fluctuates over sample rate (time)
The more snapshots, the more samples

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11
Q

Main function of an audio interface

A

Converts analog signal to digital (binary) information

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12
Q

Analog sound pressure waves representation

A

AC voltage (positive & negative charges) on a molecular level

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13
Q

Digital sound pressure waves representation

A

Binary information

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14
Q

Analog/Digital: Which has the more accurate representation of sound/waveform?

A

Analog

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15
Q

List at least 3 advantages of digital audio

A
  1. Non-destructive editing
  2. Visual editing
  3. Recall sessions
  4. Flexibility in sharing
  5. Portability in equipment
  6. Affordability
  7. Maintenance (DAWs and plug-ins have no wear&tear)
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16
Q

Information in between samples

A

Information in between samples are lost

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17
Q

Dynamic resolution formula

A

2^n = same as calculating bit in a binary word

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18
Q

Quantisation

A

The sample’s level is quantised to the nearest value based on the bit depth

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19
Q

Nyquist theorem

A

The sample rate must be at least 2x the highest audio frequency being recorded or converted
The highest frequency you can capture is half the sample rate

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20
Q

Nyquist theorem requires

A

At least one sample of both compression and rarefaction - if the frequency’s compressions and rarefactions are happening faster than the sample rate, it will not be captured correctly

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21
Q

Alias/Artefacts

A

These can be caused when the frequencies are higher than the sample rate

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22
Q

How do you get rid of alias/artefacts?

A

Anti-alias filter

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23
Q

Anti-alias filter

A

Steep low-pass filter at the Nyquist frequency which will cut off any higher frequencies

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24
Q

Standard CD quality sample rate and bit depth

A

44.1kHz sample rate

16 bit depth

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25
From standard quality sample rate, how do you calculate the next common measurements?
Double the frequency
26
Next two common samples rates after 44.1kHz
Double 44.1 = 88.2kHz | Double 88.2 = 176.4kHz
27
Standard DVD quality sample rate and bit depth
48 kHz sample rate | 24 bit depth
28
Next two common samples rates after 48kHz
Double 48 = 96kHz | Double 96 = 192kHz
29
BluRay quality sample rate and bit depth
192kHz | 24 bit depth
30
Higher sample rate and bit depth essentially means
Less information is lost because we have more samples and information within each sample (bit depth)
31
How well can you hear a difference between these standard sample rates/bit depths?
Hardly any - human hearing only goes up to 20kHz. So this is more about information retention accuracy than being able to hear an actual difference
32
Up-sampling, and does it affect quality?
Up-sampling is only used for compatibility reasons, and it will NOT affect (or improve) quality *can't have more of what you already don't have
33
Down-sampling, and does it affect quality?
We are now losing samples when we do this, therefore we will degrade the quality
34
Sample rate side effects
Jitter, phase issues, thin stereo image, drop outs, pops, clicks, etc.
35
Jitter
Digital TIMING error between samples
36
Bit depth formulas for Dynamic range and Dynamic resolution
Dynamic range: 1 bit = 6dB; n bits x 6dB = DR | Dynamic resolution: 2^n=degrees; n = bits
37
Bit depth=16 | What is the dynamic range and dynamic resolution?
Dynamic range: 16 x 6 = 96dB | Dynamic resolution: 2^16 = 65,536 degrees
38
How often and how much is a simple way to describe these two things
Sample rate and bit depth
39
Pro audio standard bit depth
24 bit
40
BluRay sample rate
192 kHz
41
Compression ratio for .mp3
11:1
42
Bit depth of audio CD
16 bit
43
Nyquist frequency of 48 kHz sample rate
24 kHz
44
Degrees of dynamic resolution of 7 bit
128 degrees
45
dBs of dynamic range of 16 bit
96dB
46
Common bit rate for .mp3
256kbps
47
Quantisation noise
Q-noise: added noise from the converters working
48
Higher bit depth affects Q-noise how?
Larger bit depth means larger dynamic range and resolution, pushing Q-noise further down to the bottom of the volume scale
49
Quality that determines frequency response of a digital recording?
Sample rate
50
Lossy vs lossless data compression
Lossless: non-destructive, temporary Lossy: destructive, permanent
51
Pro audio protocol for converting A/D & D/A
PCM
52
iTunes bit rate
256 kbps
53
ADAT channels
8
54
Bit rate of CD quality uncompressed .wav file
1411 kbps
55
Consumer protocol for stereo digital audio
S/PDIF
56
Impedance of BNC cable
75Ω
57
Impedance of AES/EBU XLR cable
110Ω
58
Professional protocol for stereo digital audio
AES/EBU
59
Cable used in ADAT protocol
Toslink - fibre-optic cable
60
Which protocol can use an RCA connector?
S/PDIF
61
Codec can be described as _____
A program
62
List the 3 AES/EBU connectors
1. XLR 2. BNC 3. DB-25
63
The Clock can be described as _____
A bit rate locking system, allowing multiple devices to move data at a controlled rate (sample rate)
64
Embedding
The process of combining audio and video down a single cable
65
Word clocks
Send out a pulse that has a timing reference (sample rate)
66
Multiplexing
Combining multiple channels of audio down a single cable
67
Advantage of using digital audio transfer protocols
It eliminates too many conversions from A/D or D/A
68
Stereo digital audio protocol that uses a balanced cable with XLR connector
AES/EBU
69
Digital audio protocols that can use coaxial cable
AES, S/PDIF, MADI
70
2 examples of lossless codecs
ALAC | FLAC
71
3 examples of lossy codes
.mp3 .m4a .ogg
72
Is m4a lossy or lossless?
It can be either depending on how it's encoded | AAC (lossy) or ALAC (lossless)
73
2 examples of uncompressed audio files
.wav | .aiff
74
Digital audio protocol that can send 64 channels
MADI
75
S/PDIF connectors
Unbalanced 75Ω coaxial cable with RCA connector | Toslink fibre-optic cable
76
List examples of multiplexing protocols
``` AES/EBU S/PDIF ADAT T/DIF MADI ```
77
3 advantages of Toslink fibre-optic cables
1. No RFI (radio frequency interference) 2. No EMI (electromagnetic interference) 3. No ground loops
78
Bit rate vs Bit depth
Bit rate: samples per second | Bit depth: how much/volume/dynamic range
79
Master clock
One piece of gear that all the digital devices will lock in with for a timing reference
80
Self-clocking
When a protocol can send clock information along with the audio it streams
81
2 things used to "draw" a digital waveform
1. Bit depth (how much) | 2. Sample rate (how often)
82
2 lowest common sample rates
44.1 kHz | 48 kHz
83
2 middle common sample rates
88.2 kHz | 96 kHz
84
2 highest common sample rates
176.4 kHz | 192 kHz
85
Bit rates unit of measurement
kilobits per second = kbps
86
Highest bit rate for .mp3
320 kbps
87
T/DIF channels
8
88
Cable used in T/DIF protocol
D-25
89
Cables used in MADI protocol
Unbalanced 75Ω coaxial cable with BNC connector | Fibre-optic cable with MADI optical connector
90
Ogg Vorbis common bit rate
560 kbps
91
Compression ratio for 560 kbps
3:1
92
Highest quality lossy file type
.ogg
93
Compression ratio for 320 kbps
4:1
94
Compression ratio for 256 kbps
5.5:1

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