Intro To Audio Engineering Midterm

Front 1

Overtones

Back 1

all freq. present in a sound

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Harmonics

Back 2

even overtones (integer multiples)

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Frequency

Back 3

the rate at which a periodic wave repeats

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Wavelength

Back 4

the point between successive crests on a periodic wave.

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Decibels

Back 5

A logarithmic unit used to express the ration between two values of a physical quantity, often power or intensity

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+10 db

Back 6

Subjectively twice as loud (perception)

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+6 db

Back 7

Objectively twice as loud (scientifically)

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+3 db

Back 8

Theoretically twice as loud (from the source)

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Equal Loudness Contours

Back 9

Show how much we have to correct frequencies so we can perceive them at the same exact level

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Threshold of Hearing

Back 10

The point at which a sound becomes inaudible

0db

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Transducers

Back 11

A device that converts variations in physical quantity, such as brightness or pressure, into an electrical signal, or vice versa

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Positive polarity

Back 12

the compression of air

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Negative Polarity

Back 13

the rarefaction of air

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Balanced Cabling

Back 14

three lines:

normal polarity (hot)

reversed polarity (cold)

and the ground wire

The receiving device flips the reversed polarity signal, effectively canceling most noise that was acquired along the length of the cable

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Unbalanced Cabling

Back 15

two lines:

the signal ("hot")

and the ground

The receiving device interprets the signal by comparing the hot signal with the ground

Any noise/interference picked up along the length of the cable it then included as part of the signal

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Most common Unbalanced Cables

Back 16

TS (quarter inch mono)

RCA

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Most common Balanced Cables

Back 17

TRS (quarter inch stereo)

XLR

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Shielded Cables

Back 18

Reduce interference, but limited to 20 ft.

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Phon

pronounced as "PHONE"

Back 19

Unit of loudness level for pure tones

By definition the number of phon of a sound equals the db SPL of a sound at a frequency of 1kHZ that sounds just as loud

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Frequency Response

Back 20

The qualitative measure of the output spectrum of a system or a device in response to a stimulus

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Dynamic Range

Back 21

Describes the difference between the loudest and quietest portions of an audio signal.

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VU Meter

Back 22

Volume Unit Meter

Displays average loudness with a slight delay

by definition, it displays the RMS (Root Mean Square) Voltage with 300ms response and release times

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Peak meter

Back 23

Displays peaks (transients)

Fast response time,

Release of actual parts can be delayed

(Controllable parameter)

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Flat Frequency Response

Back 24

accurately produces or reproduces the frequencies

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Unit for Frequency

Back 25

Hertz (Hz) "Cycles per Second)

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Timbre

Back 26

The diversity of frequency content in a sound

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White Noise

Back 27

Each frequency is played equally

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Pink Noise

Back 28

Each frequency is represented equally

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Amplitude

Back 29

Compression and Rarefaction

measured from the zero point of a wave to the peaks

Front 30

How it works:

Dynamic Microphone

Back 30

Sound pressure changes vibrate the diaphragm

The diaphragm is connected to a coil of wires

The coil of wires move back and forth over a magnet

This produces an electrical charge (the audio signal)

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Features:

Dynamic Mic

Back 31

-Relatively inexpensive

-Handle rough treatment

-Do not require power

-High threshold for feedback

// Ideal for live use

-Response is far from flat

-Simple, few moving parts

-Sturdy

-Does not require batteries

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How it works:

Ribbon Mic

Back 32

Works just like a dynamic mic, but with a small "ribbon" suspended in a magnetic field

Fluctuations in air pressure vibrate the ribbon

The ribbon is open both to the front and to the back, meaning it is subject to sound bi-directionally

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Features:

Ribbon Mic

Back 33

Subject to significant "proximity effect"

Classic radio mic and ideal vocal mic

The resulting bass boost close up results in a warm sound

The ribbon itself is quite fragile, subject to temperature change

Typically bi-directional but can be shielded

Typically expensive

Typically flat response with some bass boost

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How it works:

Condenser Mic

Back 34

A capacitor stores energy in the form of electrostatic field, between a front plate (the diaphragm) and a back plate.

Sound pressure fluctuations move the front plate

When closer to the back plate, charge current occurs (+)

When further apart, discharge current occurs (-)

As voltage is required for this, it must either have a battery orde powered by external phantom power

Front 35

Features:

Condenser Mic

Back 35

Requires phantom power

(Unless an electret condenser)

Flatter frequency response than dynamic

Generally more expensive, not as sturdy

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Phantom Power

Back 36

Provides power (48v) to condenser mics via a regular balanced cable.

XLR Pin 1 is ground, Pin 2 is Hot, and Pin 3 is Cold

Power is carried identically on 2&3

It can come from a mixer, a preamp, direct box, or a standalone device

Avoid powering anything that doesn't require power

Front 37

Proximity Effect

Back 37

A change in the frequency response of a microphone, having a directional pickup pattern, that produces an emphasis on lower frequencies

Only applies to uni-directional mics

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Pad

Back 38

Reduces the output of the microphones capsule

Some mics have multiple attenuation levels

This does not change the microphones noise floor

For use in instances of high SPL

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Factors that go into picking the right microphone:

Back 39

The frequency response/range

Dynamic range

Directional sensitivity

Polar patterns

- Omni

- Bidirectional

- Cardioid

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Point Source

Back 40

A single, locatable source

Each loudspeaker is a point source of audio

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Active vs. Passive

Back 41

Active has a built-in amp

XLR or TRS

Passive requires an external amp

speakON cables

Front 42

Features:

speakON Cables

Back 42

Reduces confusion with low-current cables

Lock into their sockets with a twisting motion (less prone to disconnection

Shielded from human touch, preventing electrical shock

The contacts do not short out during connection or disconnection

Front 43

How it works:

Dynamic Loudspeaker

Back 43

The cone is moved by a coil, which moves over a magnet via + and - AC

Dynamic mic, in reverse

Front 44

How it works:

Ribbon Design

Back 44

Ribbon mic in reverse

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Features:

Ribbon Design

Back 45

Very little mass, accelerates very quickly; good high frequency response

Fragile

Front 46

Direct Radiators

Back 46

Just a dynamic speaker without the enclosure

However, this Interferes with itself

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Enclosures

Back 47

The casing of a dynamic speaker

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Speaker Ports

Back 48

The port (vent) is carefully placed so it amplifies a band of low frequency energy

The placement of the port would change how the speaker is tuned

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Crossover

Back 49

Fixes issues with overlapping frequency ranges from loudspeakers

When multiple speakers are used, issues arise from the overlap of frequency ranges produced by the separate drivers

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Dispersion

Back 50

How sound is projected from the source of the speaker

Front 51

Horn Loading

Back 51

Increased efficiency

More focused dispersion

Front 52

Environmental Delay

Back 52

Delay in ms = 1000 (distance (ft)/1130)

Or

For every 100 feet, 90ms

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Analog vs. Digital

Back 53

A simple explanation is that "analog" represents continuous data, whereas "digital" represents discreet, divided data

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Magnetic Tape

Back 54

A typical plastic film with a coating of tiny particles capable of holding a magnetic charge

The coating is typically iron oxide or chromium dioxide

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How it works:

Recording to a tape

Back 55

the record head converts an electrical signal into a magnetic field that can be used to create a pattern of magnetization in the tiny magnetic particles of the tape

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Issues:

Magnetic Tape

Back 56

Magnetic tapes has a nonlinear response at low signal strengths (it becomes imprecise with errors

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Bias

Back 57

Fixes main issues with low-amplitude signals

Bias is added to analog tape recordings to improve fidelity

An inaudible high frequency (above 40kHz) is added to the signal before its recorded

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Tape Saturation

Back 58

A kind of analog distortion that occurs when all the particles are as magnetized as they can be

This can be used to positive effect, adding grit in particular styles of recording

This can also sound bad when overdone

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Gap loss

Back 59

Occurs when certain frequencies are mildly attenuated as a result of the gap within the magnetic heads

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Tape Hiss

Back 60

Noise caused by the finite size of the magnetic particles in the tape.

The signal to noise ratio increases at faster speeds or with wider tracks (more magnetic particles to provide greater precision)

and decreases at slower speeds or with narrower tracks

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Effects of Tape Speed

Back 61

Tape speed affects the quality/accuracy of the recording

Faster moving tape provides opportunity for more precise recordings

Slower tape speeds mark more potential for impression, including increased effects of tape imperfections

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Common tape speeds (inches per second)

Back 62

15ips - professional standard

30ips - exceptional treble response, great signal-to-noise ratio. Bass can be adversely affected

22.5ips - when audio data is connected directly to video film, audio must move at the same rate; this is the standard for 70mm film at 24fps

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Crosstalk

Back 63

Audio "bleed" between tracks on a multitrack tape

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Wow and flutter

Back 64

Variations in freq that occur as a result of instability in a tape's speed (perhaps during the recording process)

they mean the same thing, but differ in duration

- Flutter is a quick fluctuation

- Wow is a longer pitch fluctuation

Front 65

EQualization

Back 65

The process of altering the frequency response of a system (or part of a system) using simple filters

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Filter

Back 66

An amplifier that changes an audio signal through a combination of amplifying, passing, and attenuating various frequency ranges

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Pass Filters

Back 67

Lets one range of frequency through, while attenuating other ranges

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Low Pass Filter

Back 68

Frequencies below the cut-off frequency pass.

Frequencies above the cut-off frequency are attenuated (shall not pass)

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High Pass Filter

Back 69

Frequencies above the cut-off frequency pass.

Frequencies below the cut-off frequency are attenuated (shall not pass)

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Band Pass Filter

Back 70

Built around a center frequency

The "width" of that band is the bandwidth

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Most common Filter Variables

Back 71

Cutoff frequency

Q

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High Shelf filter

Back 72

* Does not attenuate below the cut-of frequency
* Instead adds the variable of "GAIN" to the frequency range above the cut-off frequency

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Low Shelf Filter

Back 73

* Does not attenuate above the cut-off frequency.
* Instead adds the variable of "GAIN" to the frequency range below the cut-off frequency

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Graphic EQ

And its variables

Back 74

* An equalizer built around multiple Band Pass Filters
* The bandwidth of these filters is "hard-wired" to ensure a reasonable crossover between - the filters
* Center frequencies are also hard-wired

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Parametric EQ

And it's variables

Back 75

* Highly controllable multiband EQ
* Bandwidth
* Amplitude
* Cut-Off
* Center Frequency or Crossover Frequency

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Dynamic Processor

Back 76

* Alters the amplitude of an output signal based on the amplitude of an input signal

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Compressors

Back 77

Decrease the dynamic range of an audio signal

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Compressor Variables

Back 78

Threshold

Ratio

Makeup Gain

Knee

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Threshold

Back 79

the point above or below which the amplitude will be changed

Front 80

Ratio:

Back 80

how much above or below the threshold the amplitude is changed

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Make-Up Gain

Back 81

gain added to the signal after the compression occurs so that the signal peaks are not too quiet

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Knee

Back 82

a softening on the threshold point

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Compressor Attack

Back 83

* How long until compression occurs after it arrives at the threshold

Front 84

Compressor Release

Back 84

* The time it takes for compression to be removed after the hold

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Compressor Hold

Back 85

* How long the compression remains after it leaves the threshold

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Pumping

Back 86

Sudden and (usually) unwanted deep gain reduction

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Breathing

Back 87

a slower return (release) to operating level with a noticeable rise of the noise floor

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Limiters

Back 88

* Limiters are employed to define the maximum amplitude that can be achieved for an audio signal, they are often employed to avoid clipping, but can not do so because they cannot respond to signals immediately

Front 89

Limiter Params.

Back 89

* Threshold
* Ratio (typically 100:1 or infinity:1)
* As fast as possible attack times (often undefined)
* Release times vary, but typically they are short

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Another Word for Noise Gate

Back 90

Dynamic Expander

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Noise Gates

Back 91

* Mute an audio signal when it is below a certain threshold

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Noise Gate Params.

Back 92

Threshold

Ratio

Knee

&

Temporal Controls

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Sidechain/Key-Input

Back 93

* The dynamic processor is not responding to the signal it is altering. It is responding to another signal (the side-chained signal)

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Delay

Back 94

an effect in which an audio signal is recorded onto a temporary storage medium and is played back after a specified interval of time

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Tape Delay

Back 95

Analogue delay: Used magnetic tape as the means to record and playback the input at a user-controlled time interval.

* Longer delays would use multiple tape decks

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Digital Delay

Back 96

Makes use of a buffer to store the audio signal for delay.

* Can be a separate piece of hardware or software.

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Digital Delay Variables

Back 97

* Delay (time interval)
* Mix (dry/wet)
* Feedback (how much of the delayed signal returns to be delayed again)
* Echoes (Measures feedback in terms of the number of echoes a given source will have)

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Doubling Delays

Back 98

a very quick delay. Intended to give the effect of doubling an audio source (30-50ms)

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Slapback Delays:

Back 99

* 75-250ms, very dry

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Reverb

Back 100

a delay-based effect intended to emulate an acoustic space (real or fictional)

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4 parts of reverb

Back 101

* Init. Impulse (the sound source)
* Establish the size of a space
* The Onset of Reverb
* Decay
* Though a room size is a variable in this, speaks more about materials

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RT60

Back 102

* The amount of time for the reflections of a sound to decrease by 60db
* Used to measure length of reverb trails

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Physical ways to produce reverberation

Back 103

* Chamber Reverb
* Plate Reverb
* Spring Reverb

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Chamber Reverb

Back 104

* Using an actual physical space to create the reverberation

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Plate Reverb

Back 105

* Creates reverberation by producing the audio source in connection to a metal plate

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Spring Reverb

Back 106

* Introduces the source signal to a spring, which vibrates in response

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Digital Reverb

Back 107

* Creates reverb through signal processing effects
* Typically includes series of delays and filters, taking into consideration variation in the stereo field (or 5.1 field or whatever)

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Convolution reverb

Back 108

* Convolution is a mathematical process for combining two functions
* In case of convolution reverb, one function is your audio signal. The other is the impulse signal of the space that is being emulated
* When well done, convolution reverb is processor intensive, but highly effective

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Direct sound : Reverb ratio

Back 109

Wet/Dy Mix

Establishes distance from source

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Binary

Back 110

The digital world, at its most basic, is a binary system.

Binary numbers exist in a base-2 counting system

Each bit is one binary digit (Binary digIT). A 0 or a 1

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Bit depth

Back 111

the amount of SPL data collected

* The number of bits that each sample consists of
* CD quality is 16 bit

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Sampling rate

Back 112

how fast the SPL data is collected

* CD quality is 44.1kHz

Front 113

Nyquist Frequency

Back 113

Half the Sampling rate;

A digital signal cannot be higher than this

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Aliasing

Back 114

high frequencies fold downward, creating new frequencies

Front 115

Anti-Aliasing

Back 115

a low pass filter with a cut-off less than the nyquist freq. should negate any possible aliasing

Front 116

Sample and hold

Back 116

* Part of the process of converting an analog signal to a digital one
* The sample is held for the length of time

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Dithering

Back 117

Adds Noise to a signal to remove digital artifacts caused by altering the bit depth or sampling rate.

Front 118

Diffraction

Back 118

the bending of waves around small obstacles and the spreading out of waves beyond small openings.