sound editing terms

7/29/2019 Sound editing terms

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Lecture 1 notes for Workshop

.AM (amplitude modulation)

A band of radio frequencies that carries information by changing the strength of the signal. Most AM

broadcasts are in mono, but many stations are adding equipment to broadcast stereo AM programs.

You must have an AM stereo tuner to receive them in stereo.

Amplifier

A separate component, or a section built into an integrated component, that strengthens the electrical

signal (increases its amplitude). A power amplifier must be connected to a preamplifier (or "control

amplifier") to switch and process the sound. An integrated amplifier combines power amplifier and

preamplifier functions in the same unit. A receiver adds an AM/FM tuner to the integrated-amplifier

configuration.

Analog

Type of audio component or recording medium that operates with signals whose waveforms are

directly analogous to the sounds they represent.

BalanceA control found on some receivers, integrated amplifiers, and preamplifiers that changes the relative

volume of the left and right channels .

Band

A particular segment of a frequency spectrum. For example, a graphic equalizer may divide the audio

frequency spectrum into ten bands, with one control to adjust the relative volume of each band. The

AM and FM bands are distinct parts of the RF (radio frequency) spectrum.

Bass

The lower frequencies in the audio spectrum, such as those produced by a string bass or bass guitar. An

instrument producing bass tones vibrates air more slowly than one producing treble tones.

BiasA very high-frequency signal added to an audio signal being recorded on tape to reduce distortion.

Type I (normal or ferric) tape requires less bias than Type II (chrome or chrome equivalent) or Type IV

(metal) tape.

Channel

A distinct path for an audio signal. Stereo signals consist of two channels, left and right, which are sent

to left and right speakers (or headphones), respectively (see separation). A surround-sound system adds

one or more additional channels, usually for the rear. Mono (or monophonic) signals have only one

channel.

Compliance

A measurement of how easily the stylus of a phono cartridge can be moved by the grooves of a record.

A high-compliance cartridge has a more flexible stylus than a low compliance cartridge.

Crossover, or crossover network

A circuit that divides lower-frequency sounds from higher-frequency sounds. Crossovers are used in

speakers that have more than one driver. In a two-way speaker system, for instance, the crossover sends

the low frequencies to the woofer and the high frequencies to the tweeter. Crossovers are also available

as separate components for use in more elaborate systems.

Crossover frequency or crossover point

In a crossover network, the frequency at which audio signals are divided so they can be routed to the

appropriate driver (low frequencies to a woofer and high frequencies to a tweeter, for example).

Damping

The application of mechanical resistance, such as a rubber or silicone material, to the cantilever pivot

to reduce the amplitude of a resonance.



DAT (digital audio tape)

A cassette that is about half the size of a standard audio cassette. The cassette shell houses a reel of

magnetic tape that contains digitally encoded audio information.

dB (decibel)

The common unit used to measure the volume of sound or an electrical signal that represents sound(also called loudness or amplitude). The decibel is a logarithmic ratio of two power levels. When

sound-pressure level (SPL) is measured in decibels, for example, a whisper is about 40 dB and a jet

engine about 120 dB. The decibel scale is logarithmic, meaning that an increase of 10 dB represents a

tenfold increase in power: it takes ten times as much energy to produce an SPL of 80 dB as one of 70

dB, even though 80 dB is subjectively only twice as loud as 70 dB. Doubling the power raises the SPL

by about 3 dB; cutting the power in half reduces the volume about 3 dB. Doubling or halving the

volume requires a change in SPL of about 10 dB.

dbx

Ordinarily, a noise-reduction system-more precisely known as dbx II--developed by the dbx company

and used in some cassette decks. This system reduces the dynamic range of the audio signal during

recording, making the soft parts of the music louder and the loud parts softer. During playback, the

processing is reversed, restoring the original dynamic range and reducing the noise added by the tape.The dbx I system is used in professional studio tape recorders. Another type of dbx noise reduction is

used in the MTS stereo TV broadcasting system.

De-emphasis

A form of equalization used in FM tuners that is complementary to a pre-emphasis used in

transmission. The purpose is to improve the overall S/N ratio (signal-to-noise), while maintaining a

uniform frequency response. Some compact discs also are processed with a frequency pre-emphasis;

these discs automatically engage de-emphasis circuits in the player.

Defeat

To bypass a signal-processing feature, removing it entirely from the circuit. Tone controls are

sometimes accompanied by a tone-defeat switch, which enables the user to eliminate their effects

without changing their settings, allowing easy comparisons of the sound with and without tone controlmodifications.

Digital

A digit is a number, and digital components use numbers in some way. A digital tuner, for example,

may only use numbers on its front-panel display, or it may use digital-synthesis tuning circuits for

improved reception. Compact discs contain a pattern representing a series of binary numbers (strings of

ones and zeros); a CD player converts these numbers into a continuously changing current that

represents the sound of the master recording. Digital audio tape (DAT) recorders turn analog input

signals into binary numbers and record these on tape; for playback, the numbers are read from the tape

and converted into an analog signal.

Dipole

A type of speaker that radiates as much sound from its rear as from its front.

Dispersion

The spread of a speaker's high-frequency output, measured in degrees.

Distortion

An unwanted alteration in an audio signal; also see THD (total harmonic distortion), noise, and IM

(intermodulation).

Dither

Very low-level noise added to a signal being digitized to reduce the high-order distortion caused by

quantizing very low-level audio signals.

Dolby B and Dolby C

Noise-reduction (NR) systems designed and licensed by Dolby Laboratories for use in consumer tape



recorders. They work by making the high sounds softer during recording and louder during playback.

Dolby C is more effective than Dolby B, but Dolby B is more common.

Dolby HX Pro

A special circuit for tape recorders - the HX stands for headroom extension - that lowers the amount of

bias added during recording when the signal being recorded already has a lot of high frequencies. This

allows high frequencies to be recorded at higher levels with less distortion.

Dolby Surround

A system developed for movie theaters, now available in add-on home components and in some

audio/video receivers, that adds two more audio channels (centrefront and rear) to the ordinary right

and left stereo channels. To derive the extra channels, a Dolby Surround decoder adds the left- and

right-channel signals together for the centrefront channel and subtracts them from each other for the

rear channel, usually sent to two rear speakers.

Driver

Any individual speaker within a system, such as a woofer or tweeter.

Dubbing

The process of making a recording of another recording. A dubbing cassette deck can record from onetape in one transport to another in a second transport. Dubbing can be done with two single-transport

decks or one dual-transport deck.

Dynamic range

The difference, in decibels (dB), between the softest and the loudest possible sounds that a component

can produce. Higher ratings are better because they indicate that the component can more accurately

reproduce the full dynamics of recorded music that is played through it.

Effects (sometimes referred to as filters)

In digital audio editing, effects or filters can be applied to sound files or tracks. Most programs use the

same terminology to describe the effects, which include:

Amplify makes a sound louder or softer.

Backwards reverses the sound wave. Bender gradually raises or lowers the sound pitch.

Delay repeats a sound once.

Echo repeats a sound with a decay.

Emphasize emphasises the high frequency parts of a sound by passing the sound through a high-pass

filter. It is the opposite of a Smooth filter. Use Emphasize command to quickly add spice to a dull

recording, such as a voice recorded from a telephone, where the high frequencies have been attenuated.

Envelope lets you adjust the loudness of a sound.

Equalizer increases or decreases the amplitude of different frequency ranges in a sound.

Fade In gradually increases the volume of a sound.

Fade Out gradually decreases the volume of a sound.

Flanger imparts a whooshing effect to the sound.

Normalize amplifies a sound to its maximum value without clipping or distorting the sound. This is

similar to applying an automatic gain control. Use this effect to raise the amplitude of a sound to its

highest distortion-free level without time-consuming, manual amplitude adjustments. A sound that is

already clipped will not be amplified. To adjust the amplitude of the sound to a fraction of its

maximum, distortion-free value, enter a value less than 100 percent.

Pitch Shift alters both the pitch and the playing speed of a sound. Used with speech, this affect can

produce voices completely different from the original. Pitch Shift changes the duration and disk size of

the sound file.

Reverb creates the combined effect of multiple sound reflections within a room, giving a smooth and

gradual decay of the perceived sound after its source stops.

The Smooth effect simulates a low-pass filter that cuts out many of the higher frequencies from a

selection. Use this command to eliminate hiss, sharp edges, clicks, pops and static from a sound.

Tempo changes the speed of a sound without changing its pitch.



EQ (equalization)

The process of changing the relative volume levels of different segments of the audio frequency

spectrum to compensate for losses or distortion at some stage of recording or reproduction. For

instance, the output from speakers can be equalized to compensate for room acoustics. Phono signals

require a specific type of playback equalization because of the equalization built into the process of

cutting a record.

Equalizer

A component, or part of a component, that is used to equalize (see EQ) an audio signal received from a

source component by dividing the signal into various separately adjustable bands. The most common

type is the graphic equalizer, which derives its name from the way its sliding controls make a rough

graph of the selected frequency changes on its front panel.

Expander

A device used to restore natural dynamic range. This is achieved by counteracting the compression of

dynamic range that occurs when recordings are made and when a signal is broadcast.

FM (frequency modulation)

A type of radio broadcasting that carries audio information by changing the frequency of the broadcast

signal. An FM station with a centre frequency of 88.1 MHz will actually broadcast a signal thatchanges from slightly less than 88.1 MHz to slightly more according to the waveform being broadcast.

Frequency

How often something vibrates or changes. Sounds are vibrations and can be represented by electrical

signals that change at different rates; a low-pitched sound is represented by a slowly changing current,

while a high-pitched sound is represented by a quickly changing current. Frequency is measured in

cycles per second, or hertz (abbreviated Hz). Most people can hear notes as low as about 20 Hz and as

high as 15,000 or 20,000 Hz. In radio, frequency refers to the wavelength of the carrier signal of the

station, such as 88.1 MHz for an FM Station or 1,010 kHz for an AM station.

Frequency balance

The relative volume of different segments of the audio frequency range, from low bass to high treble.

Logic

In cassette decks, the ability to switch from one transport function, such as fast forward, to another,

such as rewind, without first pressing the stop button; doing this in decks without logic controls can

damage the tape. In a surround-sound system, logic circuits are used to process encoded signals.

Loudness compensation

A form of equalization that progressively emphasizes low frequencies (and sometimes high

frequencies) as volume is reduced. Loudness-compensation circuits, which appear in some

preamplifiers and receivers, compensate for the human ear's loss of sensitivity as the sound level

decreases.

Microphone

An electroacoustic pickup device that converts acoustical energy - such as live music or a voice - into

an electrical signal that is essentially equivalent in shape and amplitude to the acoustical input.

Midbass

The segment of the audio frequency spectrum covering sounds produced in the upper bass and lower

midrange region; special midbass drivers can be used to reproduce these frequencies.

Midrange

The segment of the audio frequency spectrum between the bass and treble frequencies. The midrange

includes most voices and the fundamental tones produced by most musical instruments. Midrange

drivers reproduce sounds in this frequency range.

Mix

In post-production, blending many soundtracks into one (monaural) or two (stereo) to create a finished

program.



Mono (or monophonic)

An audio signal in which all the information is combined in one channel; also, a component that

handles only one channel, such as a mono amplifier (used in pairs for stereo programs).

Multitrack

An audio recorder, using either tape or computers (disks, memory chips), that can record and play back more than two tracks, usually multiples of four or eight.

Noise

An unwanted part of a processed signal that is not related to the original signal. Audio noise usually

sounds like hiss. Some audio editing programs have a Noise Gate effect or filter that can remove

excessive hiss or background noise from a sound. You can also use it to remove silent gaps in a sound.

Non-linear

Any form of video editing that doesn't record to a single, master tape. Once referred to systems that

used banks of VCRs or laserdisc players, now refers almost exclusively to digital editing on a

computer. The logical opposite, "linear editing," was never used very much.

NR (noise reduction)A system designed to reduce the noise added to an audio signal during recording.

Output level

A measure of how strong a signal produced by a component is, usually in relation to the strength of the

signal put into it.

Oversampling

A digital filtering technique used in some compact disc players. The 44.1-kHz signal from the CD is

sampled at some multiple of that frequency (usually two or four times), which raises the frequencies of

any spurious signals created by the digital recording process well above the audio range. The spurious

signals are then removed by an analog filter with a gentle slope, which is said to cause fewer phase

irregularities than the sharp-cutoff filter required when oversampling isn't used.

Peak indicator

Usually a flashing LED on a tape recorder that indicates when transient signal levels have exceeded the

recorder's ability to handle them without distortion; a supplement to recording-level meters.

Post-production

The third and final stage in a film or video project. Concerned with editing the picture and sound, then

generating the finished master version. In slang, simply "Post."

Pre-production

The first of three stages in a film or video project. Concerned with research, writing scripts, and

planning.

RCA connector

The most common kind of connector for home audio systems, using small, one-pin phono plugs. The

cables usually come in pairs, with the right channel marked in red and the left channel in black, grey, or

white.

Recording-level meter

An indicator on a tape recorder that displays the signal levels being recorded onto tape from moment to

moment; used to set proper recording levels. Most analog and digital audio equipment allows you to

adjust recording and playback levels. For best results, adjust the output level of the device playing the

sound to its maximum without clipping. Recording levels show the levels for input. If a red light

appears on the display, the signal from the analog-to-digital converter is clipped. To correct this

problem, turn down the input source.

Playback levels show the levels for output. Red lights indicate that the sound is clipped. To avoid

clipping, lower the playback levels.



Sampling frequency (or rate)

In digital audio, the number of times a signal is sampled each second. The standard sampling rate for

the CD (compact disc) format is 44.1 kHz, which means each second of sound is encoded by 44,100

numbers for each channel. Higher sampling rates yield better sound fidelity and larger sound files. Use

lower sampling rates if you want to save disk space. Before recording, always choose the highest

sampling rate that your hardware supports. When finishing a sound, select a sampling rate supported by

the destination computer. Sample size determines the resolution of each sample. The most widelysupported resolution is 8 bits. CD-quality sounds use 16 bits.

Shot

What the camera sees, the basic unit of a film or video. Typical shots are:

Close-up - fills the frame with one person's head or face.

Medium shot - includes the head and upper body.

Long shot - view that includes much of the environment around the subject.

Establishing shot - usually a wide view that creates a sense of place.Macro - extreme close-up of very small objects such as coins, postage stamps, etc.

Sound

Here are some common terms related to sound for audio-visual and multi-media production:

Effects - sounds other than spoken words or music.Mix - creating a complete sound track by re-recording multiple tracks into one or two while balancing

each sound for the proper effect.

Sync - sound matched to video, usually voices recorded while shooting.

Track - a linear assembly of sound in program order; multiple tracks may contain voices, narration,

music, or effects.

Stereo

Sound with two separate, usually "left" and "right" channels.

Subwoofer

A separate speaker designed to reproduce only bass frequencies. Subwoofer systems sometimes contain

an amplifier and a crossover network.

Super

Short for "superimpose." A visual effect in which one image is placed "atop" or "in front of" another,

as when a person's name appears over their picture during an interview.

Supertweeter

A tweeter used to reproduce only extremely high frequencies; usually found in four- or five-way

speaker systems.

Time code

A digital code which identifies each frame of video, recorded on the tape. There are two common time

code systems. SMPTE (60Hz) and EBU (50 Hz).

Time-lapse

The technique of condensing time by increasing the interval between frames while recording; often

used to show flowers blooming, the sun or mooon rising, etc. Also known as "time-lapse photography."

Titles

Any text displayed on the screen. The name of the production, displayed on the screen, is the "main

title."

Treble

The high part of the audio frequency range.

Tweeter

A driver in a speaker system that is designed to reproduce treble sounds (high frequencies).

Videocassette



Videotape and reels enclosed in a case for convenience. Formats include:

8 millimeter and VHS - home videocassettes, the former using tape 8 mm wide, the later tape 1/2 inch

wide.

High-8 and Super VHS - developments of 8mm and VHS using "S-video" recording method for images

of higher quality; will not play on conventional 8mm or VHS machines.

Umatic- or "3/4-inch" - videocassette using tape three-quarters of an inch wide; used extensively in the

1970s and early 1980s, but now obsolete. Betacam and Betacam SP - not to be confused with "Betamax" home format; professional

videocassette using 1/2-inch tape; Betacam SP is a slight improvement to Betacam picture and sound

quality.

Digital Betacam - digital videocassette recording system designed to be in some ways compatible with

standard Betacam and Betacam SP.

D-1, D-2, etc . - digital recording formats promoted by various manufacturers.

Volume

Usually expressed in decibels (dB), the strength of a sound wave or audio signal.

Wipe

A transition between scenes in which one image appears to cover another; stars, irises, shutters,

checkerboards, and countless other patterns are available.

Woofer

A driver in a speaker system designed to reproduce the low, or bass, part of the audio frequency

spectrum.

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