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AC:- Acronym for Alternating Current,
which is electrical current where electrical charge will travel
in one direction, then change into moving in the opposite direction.
When looked at through an oscilloscope, it's waveform
is generally of a sinusoidal, square or sawtooth shape. Almost
all domestic electricity found in homes is AC, with a frequency
of 60 Hertz, Although virtually all electronic
devices require DC power (batteries are DC)
this is rectified through the use of transformers
and rectifiers
in the devices power supply. The reason why AC has been chosen
as the standard for mains electricity when DC may be more suitable
is due to it's abilty to be tranferred over great distances. See
also DC and Rectifier.
AC Bias:- See "Bias".
A Cappella: - Music which consists only of voice or voices,
and is bereft of any instrumental accompaniment.
Acoustics: - The study of sound and its behaviour within
an environment.
A/D Conversion / Converter: - Analogue to Digital
conversion. A converter is a piece of circuitry
which acheives this. The quality of conversion is highly dependent
on the amount of bits used in the conversion process, hence a
24 bit converter will acheive a much more accurate resolution
of the sound than say, an 8 bit converter.
Additive Synthesis: - see Sound
Synthesis .
"A.D.S.R.": - Attack, Decay, Sustain, Release.
See also "synthesiser"/"envelope
generator"
AES: - Acronym of the Audio Engineering Society.
After Touch: - facility of some keyboards which allows
the sonic quality of a note to be altered by further pressure
after the key has been initially depressed.
AIFF: - Digital sound format closely
associated with Mac computer, but used on other platforms. Acronym
of Audio Interchange File Format.
Algorithm: - Step by step solution to a mathematical problem.
In software, a "routine" designed to realise some specific
task.
Aliasing: - See Nyquist
Theorem .
Alignment: - see "azimuth alignment".
Alignment Tape: - Tape using several specific tones, used
for the optimisation of azimuth alignment (see below) on tape
machines.
Ambience: - In audio / acoustic terminology, this is the
reverberant quality of a room.
Ampere / Amp: - see Current.
Amplitude: - the level of a signal.
Analogue: - A continuous electrical signal whose amplitude
varies with time.
Anechoic / Anechoic Chamber:
- Anechoic means an absence of echo / reverberation.
An Anechoic chamber is a room that has been acoustically designed
to have no echo. Quite a hard thing to do, it is realised by the
use of materials that will completely absorb sound waves, and
is important for the testing of loudspeakers etc.
Arpeggio / Arpeggiator: - When the notes of a chord are
played one after the other (sequentially), rather than all together
(concurrently), this is an arpeggio. An Arpeggiator is a hardware
device or software which will automatically create an arpeggio.
Attack: - In music, it is the period between the note
being struck, and it's peak in terms of sound pressure level.
It could be described as being a sounds initial transient.
Attenuate / Attenuation / Attenuator: - In sonic terms,
this means reducing the level of something. An attenuator is a
device which reduces the level of a signal.
Audio Frequency: - Frequency which
falls within the range of human hearing, and measured in Hertz (20Hz - 20,000Hz) . See
frequency for fuller explanation.
Autolocator: - Feature of some tape machines which enable
a specific location on a tape to be stored, so that later, the
tape machine may locate the same cue point.
Azimuth (alignment): - Degree of alignment between tape
head and tape. Perfect azimuth alignment is when the tape head
and the tape are both are making a perfect 100% contact with each
other. When this is the case, alignment is said to be at it's
"zenith", and it is exactly 90 degrees between the tape-head
gap, and the longitudinal axis of the tape. Good azimuth alignment
is vital to the sound quality produced by any kind of tape machine,
with poor quality alignment, a tape machine will often sound muffled,
and somewhat lacking in "top end". Poor azimuth alignment
is largely responsible for the inferior sound quality produced
by many cassette recorders.
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Baffle: - The part of a loudspeker enclosure on to which
the drive units are fastened. Alternatively, a sound absorbent
barrier used in recording studios to separate musicians who are
recording in the same room (sometimes referred to as a "gobo"
in this sense). Hence a "well baffled speaker" is not
a speaker that is in a state of some confusion! but rather, it
is a loudspeaker which has been firmly fixed to a rigid base-board.
Balanced / Balanced Line: - An audio cable, most commonly
a three pin "XLR"
type mic cable, which has two conduction channels
surrounded by metallic shielding where each conductor is of equal
impedance relative to the ground/
earth. The conductors should have equal potential but opposite
polarity. The advantage of this system is in terms of noise reduction,
as a balanced line reduces unwanted noise because the opposing
polarities ensures that unwanted noise is lost through "cancellation"
when the inverted signal on one conductor is added to the original
signal of the second conduction channel when the whole of the
signal reaches it's destination.
Bandwidth: - Generally this is the amount of information
which may be carried by a specific device, eg a modem may carry
a maximum of x amount of bits per second, and that is said to
be it's "bandwidth".
In music and sound, "bandwidth" may be the difference
or "spread" between the lowest and highest frequencies
that are capable of being produced by a piece of sonic circuitry
(eg amplifier, computer soundcard etc) or musical intrument, where
the "spread" between the frequencies corresponding to
the lowest and highest notes would be regarded as the "bandwidth"
of the instrument.
In a case of radio however, one could also speak in terms of
the bandwidth that is capable of being received (as opposed to
produced). This could be illustrated by saying that a radio that
is capable of receiving signals within the bandwidth between
88 and 108 Mhz could be described as being an "F.M."
radio.
Band Pass Filter: - A filter which
allows only certain audio frequencies to
pass, while rejecting all others above and below the cutoff points.
An example of a bandpass filter may be found in a "3 - way"
loudspeker system which will utilise a "woofer" for
bass frequencies, a "midrange" unit for middle frequencies,
and a "tweeter" for high frequencies. Whilst the woofer
(which has no frequencies below it) will be able to have it's
band of frequencies fed to it via a "low pass" filter
and the "tweeter" which has no frequencies above it
will have a high pass filter, the midrange, which will have frequencies
both above and below it's area of operation will need to have
its frequencies fed to it via a bandpass filter. See also "Crossover".
BJT: - Acronym of Bipolar Junction Transistor.
Bias: - Current / Voltage
which determines the intrinsic "noise
floor" of an audio device (measured in db's)
... Also AC bias (tape recorder) ... This is
where bias is defined as an ultrasonic
signal, which is usually found between the frequencies
of 100/200 k Hz.
This signal is incorporated with the conventional audio signal
(via the record head) to reduce hysteresis
induced harmonic distortion. The "bias"
of a magnetic tape ("Metal", Chrome", "Normal"
etc) refers to a bias signal which is roughly optimal to the kind
of magnetic material that has been used in the manufacture of
the tape. See "hysteresis" for more
information.
Bi-Directional (microphone): - Microphone that will pick
up sounds which are emanating from the front of the microphone
(on-axis), and the rear of the microphone (off-axis), and largely
reject those to the side. Also described as a "figure of
eight" microphone, as the field pattern just described corresponds
to that of the figure eight.
Binaural: - Hearing with two ears, humans who are not
deaf in one / both ears hear things "binaurally".
Bit: - Smallest unit of digital currency,
and the basis of the binary numbering system (bit is a shortening
of "binary digit). A bit may be either 0 (off), or 1 (on).
Eight bits make a Byte (see below).
"Boomy": - A subjective term used to describe
sound recording - mix etc which has an excessive amount of bass.
"Break-Jack": - See Normalised
/ Normalled Connection.
Buffer: - A temporary storage location in memory, where
data may be accumulated until it is ready for processing.
Bug: - Software error. A term that originally comes from
the early days of computing, when a problem in an early military
research computer was found to be caused by a moth inside the
machine!
Bus: - In recording parlance, a bus is one of the main
outputs of a mixer, which may be connected to one of inputs of
a recorder, amplifier or signal processor. In computing parlance,
it is the means by which data is transported between one part
of a computer (eg Central Processing Unit) to another (eg Hard
Disk). A computing type of bus may be separated into two parts,
an address bus, and a data bus, and is measured in terms of its
"width" in terms of bits (how many bits of data it can
move at one time).
Buzz: - Annoying audio noise, created by harmonics at
the 60 Hertz (the frequency of AC electricity) part of the sound
frequency spectrum.
Byte: - A grouping of eight continuous bits, which are
collectively known as a byte.
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Capacitor / "Cap" / Condenser: - Electronic
component which lets lets Alternating Currents
through, but stops Direct Currents. Along
with the transistor
and the resistor,
it is one the most common components in electronics.
Capstan: - slim roller on tape machine which along with
a pinch roller,
helps to maintain the correct tension of the tape relative to
the tape head.
Cardioid: - see Polar
Pattern.
Cent: - A musical cent is one hundredth of a semitone.
Chip: - Another word for an Integrated
Circuit / Microprocessor.
Chromatic Scale: see scale.
Chorus: - Signal processing which creates an electronic
simulation of a chorus by combining a signal with a delayed copy
of itself. Often, the delay time and level of the copy is continuously
varied in the interests of added "reality". This part
of the process is known as flanging, often used as an effect in
itself.
Circuit: - When electrical components (eg transistors,
resistors,
capacitors etc, are connected in a way that utilizes the central
electrical / electronic concepts of current (see below), voltage,
and resistance
to perform some task, this is a circuit.
Circuit Board: - Convenient, flat layer on which the electronic
components that make up a circuit may be placed, often containing
metallic, conductive strips to connect the components together.
Clipping: - When the amplitude of a signal exceeds the
maximum possible level of a device, the part of the waveform which
is excessive is "clipped" resulting in a distortion
of the sound. If clipping is harsh and prolonged, this can result
in damage to the device in question. See also "Headroom".
Close Field: - See Near
Field .
Coincident Pair: - If a pair of microphones are mounted
together, so that the capsules are at a 45 degree degree angle
(which is is the optimum position for picking up a nice two channel
stereo sound field), then the two microphones in question could
be described as being a " co-incident pair".
Complex Wave: - see Wave.
"Compression / Compressor": - see Dynamics
Processing.
Concert Pitch: - See Pitch.
Condenser: - Old term for a Capacitor (see above).
Condenser Microphone: - Microphone which works on the
principles of Capacitance and the Capacitor (see above). When
the diaphragm of the capacitor vibrates in response to soundwaves,
the Capacitor's ablity to hold charge varies. This measured change
is the transduction of sound waves into electrictal signal. As
the plates of the Capicitor need to be fed with charge everytime
the mic is in use (an exeption to this is the "electret condenser"
see below), an external source of power is required, usually a
supply of up to 48 volts DC, which is also known as "phantom"
power, as the power is carried throgh the same cable as the audio
signal.
Condenser microphones offer the greatest fidelity in terms of
tranducing soundwaves into an electrical signal, however, they
do have the disadvatages mentioned above, as well as a great sensitivity
to picking up hums/ ground loops etc, and a delicacy which renders
many of them more suitable for studio, rather than stage use.
Even then, many of them have to be used in conjunction with a
special "cradle" which inhibits interference from external
sources. However, there is no substitute for the fidelity and
beauty of sound as rendered by a great "large - plate"
condenser microphone.
Conductor / Conductive: - Any material which offers very
low resistance
to an electrical current passing through it.
Opposite of insulator. Examples of good conductors
include Gold, Silver, Copper and Aluminium. See also Ohm,
Resistance
Current etc. Also a musical term for someone
who waves a stick at an orchestra.
CPU: - Acronym of Central Processing Unit
aka microprocessor. See microprocessor
for a full definition.
Crest Factor: - When the peak value of a signal is divided
by its rms
value, this is said to be its Crest Factor.
Crossover / Crossover network: - As
most loudspeaker systems use two or more specialized drive units
which individually only cover a part of the frequency
spectrum ("woofer" for bass frequencies "tweeter"
for treble etc), some kind of circuit is needed to separate the
bands of frequencies which are appropriate for each of the drive
units, this is a crossover. There are two primary ways of doing
this.
Active Crossover: - One is to split the frequencies into
different bands (bass, mid, treble etc) before the signal is amplified.
This is known as an "Active" kind of crossover network.
This "Active" way of splitting the frequency bands is
usually used where multiple power amplifiers (eg one amp for bass,
one for mid and so on) as well as multiple drive units are used.
An example of this would be a large sound re-inforcement or "PA"
system of the kind seen at large rock concerts etc, whose power
output may be many thousands of watts.
Passive Crossover: - Most domestic "Hi Fi's"
of lower power use what is known as a "Passive" crossover
system, where the frequencies are split after the signal has been
amplified.
High pass / Low pass / Band pass:
A high pass filter utilizes capacitors,
as the impedance of a capacitor decreases for HIGH frequencies,
this enables it to ensure the passage of higher frequencies, and
stop the passage of more powerful, lower frequency signals which
may blow the poor little tweeter unit to smithereens!
Conversely, a low pass filter utilizes
an inductor or "coil", so called as basically it is
a coil of wire of a certain length wrapped around a magnet. The
"conversely" bit is that an inductor has a lower impedance
for LOW frequencies, hence, it is useful as a low pass filter.
Use both a capicitor and inductor in parallel, and you have a
band pass filter, rolling
off frequencies both above and below the appropriate roll-off
frequencies, and useful for speakers which utilize a "mid-range"
unit.
Crosstalk: - When one electronic signal begins to interfere
with another electronic signal, this interference is referred
to as crosstalk.
Current: - A flow of electrical charge through a electronically
conductive material. Usually measured in Ampere's (Amps A). 1
amp repesents 6.24 x 1018 "charge carriers", which are mostly
electrons or electron deficient atoms.
Cutoff Frequency: - The frequency
where the output of a filter, speaker etc
is 3 Decibels per Volt lower than its maximum level. A loudspeakers
/ amplifiers / microphones frequency response is usually designated
by this form of measurement.
Cycles Per Second: - See Frequency.
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D/A Conversion / Converter: - Digital to Analogue
conversion. A converter is a piece of circuitry
which acheives this. The quality of conversion is highly dependent
on the amount of bits used in the conversion process, hence a
24 bit converter will acheive a much more accurate resolution
of the sound than say, an 8 bit converter. This aside a good "rule
of thumb" for measuring the quality of D/A and A/D converters
is to examine the S/N or "Signal to Noise" ratio of
the device in question, which is measured in dBs.
D.A.T. - Acronym of Digital Audio Tape.
dbx: - Form of noise reduction patented by the dbx corporation
of the United States. Works by compressing
the sound during recording, and expanding it
during playback.
DC: - Acronym for Direct Current,
which is electrical current where the flow of electrical charge
is ALWAYS in the same direction. Whilst almost all household elctricity
is AC, the power produced by batteries is invariably
DC. See also AC. When looked at through an
oscilloscope, DC electricity produces a nice, even Sine
Wave.
Decibel (dB): - A logarithmic measure of sound pressure
level, a "Decibel" is one tenth of a "Bel".
To put this in human terms, someone with pretty good hearing will
be able to pick up sounds from @ 0 - 10dB (a quiet room can be
as much as 40dB), and will start to feel pain and possibly sustain
hearing damage if they are exposed to levels in excess of 135dB
for any length of time (The public address speakers of the kind
used at very large concerts may realize this if they are running
at their maximum).
De-esser: - Signal processing device used to cut down
on the sibilance or "hissy s's" which can sometime affect
speech and singing through a microphone. This is usually through
use of the techniques of high frequency compression
combined with equalisation.
"Delay": - see Effects or "FX"
Processing .
Detent: - A stop or catch. In electronics usually placed
in a variable resistor such as a the middle point of a "pan"
control on a mixing desk, to tell you where the "default"
setting is.
Diatonic Scale: - See scale.
Digital: - The use of Binary data to represent information,
"Binary" meaning that the highly complex data (audio, video, whatever) has been
broken down into many values which have one of two states, positive
and non positive. Positive is represented by 1, and non positve
by 0. Each value is known as a "bit". For more on "Digital" within
an audio context, see Sample.
Direct Injection (DI) Box: - Transfomer device which allows
a musician to plug an an electronic instrument such as a guitar
or bass, directly into one of the inputs of a mixing desk.
Directional Pattern: - see Polar
Pattern.
"Dry" Signal: - Signal which is bereft of any
processing, such as eq, gating, reverb and the like. Opposite
of "wet"
signal.
Dynamics Processing: - Processing which alters aspects
of the dynamics (difference in sound level) of an audio
signal. Common examples are...
"Compression": - ("squashing" the
sound so that the difference between highest and lowest level
of the sound is lessened. This usually means amplifying lower
level signals, resulting in a sound that is perceived as louder
and more "punchy"), the reverse of this is "expansion"...
"Noise Gating"(cutting the signal for very short
periods of time when it falls below a certain level - useful as
a form of noise reduction and occaisionally as an effect in itself).
Dynamic Microphone: - Microphone which works through a
diaphragm being attached to a coil which operates within a strong
magnetic field. The diaphragm vibrates in response to soundwaves,
which, in turn stimulates motion of the coil. The magnetic field
causes an electric current to flow through
the coil, with a voltage
which varies in sympathy with the motion of the diaphragm. This
measured change is the transduction of sound waves into an electrical
signal. Not as good in terms of fidelity as a condenser
type of microphone, but more sturdy and less prone to noise interference,
hence it's wide use on stage, or where a certain kind of "grittiness"
is required.
Dynamic Range: - Difference in signal level between the
loudest and quietest parts of a performance / recording etc. It
is measured in decibels. Incidentally, the dynamic range of the
human ear is said to be @ 130 dB.
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Earth: - see ground.
Earth Loop: - see Ground Loop.
Echo: - Reflected sound that arrives at the ear of the
listener after the direct sound. Not to be confused with reverberation,
which is more of a gradual decay of a sound resulting from mixture
of multiple echos, rather than a "bounce - back", where
each echo may be heard distinctly.
Effects or "F.X." Processing: - Processing
of audio signal in order to:
a) attempt to create a particular kind of acoustic environment
or "atmosphere", or
b) make strange/funny sound effects!. Common examples
include
"Reverb": - (device which simulates reverberation,
which primarily changes our perception of the acoustic environment
in which music is recorded or played), and
"Delay": - (device which will repeat sound
at regular intervals producing echo-like effect).
c) attempt to replicate something eg a Chorus.
Effects return: - Connector, control, and/or path where
a processed (wet) signal from an from a signal processing device
enters a mixer. The enables the level of influence of the "wet"
signal to be influenced via a potentiometer
on the mixing desk.
Efficiency: - With loudspeakers, efficiency is generally
the Sound Pressure
Level (measured in Decibels) produced
from a given watt of an amplifiers signal (dB's per Watt). A very
efficient speaker can have a bigger influence on the SPL's produced
by a system than the level of watts produced by the amplifier.
A good rule of thumb is that a speaker that 3 dB's more efficiency
per Watt that another speaker will be twice as efficient, and
will be capable of producing the same amount of dB's from an amplifier
with say, a 50 Watts power output, as the less efficient speaker
would with an amp which has a hundred Watts power output. To put
it another way if one speaker has an efficiency rating of 100
dB's per Watt, and another speaker has an efficiency of 103 dB's
per Watt, the second speaker will not be @ 3% more efficient,
it will be @ 100% more efficient!
Electret Condenser microphone: - Condenser
microphone where the condenser / capsule is kept in a constant
state of charge.
EMF (ElectroMotive Force): - See Voltage.
Envelope: - Factors which determine how a signal / sound
changes over its period of existence. See also Sound
Synthesis (envelope generator).
Envelope Generator: - see "Sound
Synthesis" .
Error Correction / Error Detection: - Error detection
is the process of determining whether any bits
in a piece of digital audio have been lost. Error Correction is
the process of replacing these lost bits.
Equalisation or "EQ": - Signal processing device
which alters the frequency response of an
audio signal. There are several types of equalisation, notable
examples being "Graphic EQ" and "Parametric EQ".
Equalisation may be used to help acheive the desired "flat"
response in a performance / recording (perhaps to correct
acoustic defincies in the local environment),
or used to alter more un natural levels of frequency response
as an effect in itself (modern djs / remixers tend to like doing
this alot).
Event: - Any single piece of MIDI
data is referred to as an "event", eg a note being triggered,
the velocity
of the note, a program change etc.
Expansion and Expander:- A form of Dynamics
processing. When lower level signals are lowered (attenuated)
and higher level signals are raised (boosted), this is expansion.
A devise that acheives this through circuitry
or software is called an expander. This is the opposite of compression.
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Fader: - Sliding potentiometer
which may increase or attenuate (the fade bit!)
the gain of a signal. Usually associated
with a mixing desk.
Fade-In / Fade-Out: - Gradually increment (fade in), or
decrement (fade out) the level of a signal.
Fairlight: - Very early computer based music/ sampling
workstation, developed in Australia through the mid/ late seventies
by Peter Vogel and Kim Ryrie. It was relased in 1979 as the "Fairlight
Computer Musical Instrument", it's most notable early users
being Peter Gabriel and Stevie Wonder. Along with the American
Synclavier, it went on to have a very significant impact on the
music of the 1980's. Much more info here.
Feed: - In signal routing terms, this is where an output(s)
from one device that is sent into the input of another.
Feedback: - When the sound being produced by the output
signal (from a loudspeaker) is picked up by the input (in a kind
of circular loop). When feedback reaches a certain level it causes
an exponential rise in the level of certain frequencies, such
as the screaming howl familar to guitarists and microphone users,
or in the case of lower frequencies, a kind of ever increasing
rumble.
FET: - Acronym of Field Effect Transistor.
Figure of Eight microphone: - see Polar
Pattern.
Filter: - Electrical circuit designed to boost or attenuate
certain frequencies within the sound spectrum.
Final Mix: - When a multitrack
recording is mixed down into a two channel stereo recording (master).
Flanger / Flanging: - When a signal is combined with with
a slightly delayed, modulated form of itself.
"Flat" (frequency) Response: - When an amplifier
/ microphone / loudspeaker displays an even frequency response
(an even efficiency of frequencies within its
bandwidth). This is usually defined as being
within 2 dB's .
Frequency: – The amount of times
that a wave
repeats per second, measured in Hertz (which are cycles per second)
after Heinrich R. Hertz the man who devised this form of measurement.
Or to put it another way, if a soundwave vibrates the air x amount
of times a second, this could be said to be it's frequency in
Hertz. A young human who hasn't abused their ears (unlike most
of the visitors to this site!) will be able to detect frequencies
roughly in the range of 20 - 20,000 Hertz. However, as we get
older and/or abuse our hearing listenting to loud music etc, this
may gradually roll off so that an older person / Death-Metal fan
may only be able sounds up to the frequency of say, 16,000 Hz.
Our ears become progressively less sensitive to sounds below 500
Hertz, and they are at their most sensitive to sounds which have
a frequency of @ 3-5kHz.
Frequency response: - Difference or "spread"
between the lowest and highest frequencies that are capable of
being produced by a piece of sonic circuitry
(eg amplifier, computer soundcard loudspeaker etc).
Fundamental Frequency: - Nearly all sounds are made up
of a Fundamental Frequency, which is the lowest frequency, and
a collection of Harmonics, which are higher
frequencies at stepped increments. It is the fundamental which
gives us the the main frequency / pitch of the sound, and the
interaction of the harmonics further up the frequency scale which
gives us the essential "character" or "Tone Colour"
of the sound.
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Gain: - level of amplification of a given signal... Sound
professionals tend to use this term where the layman may say "volume".
"Gain Riding": - The art of constantly adjusting
the gain control of a mixing desk, amplifier etc in order to get
the maximum possible level of amplitude (signal level) without
going too far, and creating distortion though overload.
"Gang", "Ganged" etc: - In electronics,
this is where two or more controls / sockets etc operate together,
and changing one will automatically affect the other, as they
are running in parallel.
Gap: - In tape recorders, the "gap" is the distance
between the magnetic poles of the record, playback and erase heads.
"Gate": - see "Dynamics
Processing" .
"General" MIDI (GM): - See MIDI
.
Generation Loss: - A loss of sound quality between subsequent
generations of an analogue recording (usually
tape, where a copy of a copy of a copy may sound noticably inferior
to the original recording). This is not a problem with digital
recording, so long as it is not converted into analogue. This
is due to the fact that in its most basic level, the copying of
a digital recording is a copying of a vast amount of binary numbers,
which can be checked.
Glide: - An effect where a note / pitch is decreased by
a semitone, then "glides" its way back up to the original
pitch.
Gobo: - See "Baffle".
Ground: - In electronics, this is a terminal which has
no voltage,
(known in the UK as "earth"). Both names arrive from
the fact that the eventual end point of the ground / earth channel
in an electrical system (eg mains electricity) is a conductive
metal spike which must be in contact with the ground / earth, where any
voltages are dissipated.
Ground / Earth Loop: - A condition which may occor in
an electrical system where there is more than one Ground connection
(see above), which causes a circulation, or looping of currents
between ground points with cable resistance
transforming this into fluctuations in voltage. Its symptom is
a low hum @ 50 - 60 Hertz (see Frequency).
If you are in the US it will be 60, in Europe 50.
"GS" MIDI : - See MIDI
.
Guide Vocal: - When a vocalist records an initial vocal
track for a multitrack recording which acts as a "guide"
for other musicians who record their parts later. When the other
tracks are recorded, this is usually then replaced with a "final
vocal".
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Half Step / Half Tone / 1/2 Tone etc: - American terms for a semitone.
Harmonic(s): - With the exeption
of an electronically generated pure sine wave All of the sounds that we hear gain their essential "character" through the presence of harmonics, which are (in the case of music
and audio) soundwaves whose frequency rises
in incremental steps from a Fundamental frequency. To use
an example, say there was a sound with a fundamental frequency
(or if we were being musical, a note or pitch) of 100 Hertz. the "first" harmonic of this would have a frequency that
was exactly double this (200Hz), the "second" would
be double that (400) and so on. If this were a note, its pitch
would corresond to the fundamental frequency of the sound, however
the subtle interaction of these higher frequency harmonics of
varying amplitudes (levels), will give the sound its "timbre"
or "colour". Hence a guitar playing E4 will sound considerably
different from a piano playing E4, although the fundamental frequency,
or pitch will still be @ 329.63 Hertz (if they are correctly tuned!).
Harmony: - As all the musicians will know out there will
probably know, harmonic concepts are the primary basis for the
contruction of music theory, eg "chords" and the concept
of playing music in a "key" are built around the notion
of having a fundamental note, with a series of notes higher in
pitch than this, their pitches being in harmony with the fundamental
note, in line with the harmonic principles mentioned above.
Harmonic Distortion: - When harmonics are present in an
output signal which weren't a part of the input signal of an audio
device, this is referred to as harmonic distortion.
HDR: - Acronym of Hard Disk Recorder. Any digital audio
recording device which is based on a computer type hard disk storage
device, rather than D.A.T. (Digital Audio Tape), CD etc.
"Headroom:" - The difference in dB's or watts
etc between the highest level of a sonic signal that is
being produced, and the highest level that is capable
of being produced without significant distortion/ spontaneous
combustion! A sonic system always sounds at it's best when it
has lots of headroom, and at its worst when there is no headroom
at all, as clipping may result.
Hertz: - See Frequency .
High Pass Filter / HPF: - A filter
which attenuates frequencies
which are below it's stated cutoff frequency. See also "Crossover".
Hypercardioid: - see Polar
Pattern (cardioid).
Hysteresis:- In a general sense, "hysteresis"
can be explained by pressing on an object that yields, if when
you release the pressure, the object doesn't quite spring back
to the shape that it had before, then it is displaying hysteresis.
In recording, this term is used mostly in relation to magnetic
tape, and other devices which utilize magnetism (eg the magnetic
fields of a microphone etc). With magnetic tape, it is when the
magnetization of the tape lags slightly behind the electro-magnetic
field produced from the recording head, creating a kind of distortion.
This problem is partially overcome with the use of high frequency
(around 100-200 k Hz) inaudible signal,
which is known as an (AC) "bias"
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Impedance: - At it most general electronic level, impedance
is the amount of resistance
and / or reactance offered by an electronic circuit
or device to the (AC) current
which flows through it. It is commonly represented by the mathematical
symbol "Z", and is measured in Ohms.
Some people may have had an unwelcome brush with the laws of impedance
when (usually drunk at a party!) they attempt to wire several
speakers to each channel of their amplifier, then witness the
scene of expensive electronic carnage which usually follows!
Keeping with speakers and amplifiers, impedance in terms of Ohms
is usually measured nominally (an average of the various levels
of impedance measured throughout the scale of sound frequencies
eg a typical loudspeaker with a nominal impedance of 8 Ohms may
vary in impedance between 3 and 30 Ohms!) a speaker with a lower
nominal impedance (say 4Ohms as opposed to 8) will offer less
opposition to the power which the amplifier provides Amplifiers
will also have a specifed minimum impedance rating, which is the
lowest load (in terms of Ohms) that the amplifier is capable of
driving. The lower the nominal impedance of the load, the higher
the power (in terms of Watts) delivered to the speaker.
Returning to the "drunken party" scenario, if you connect
a 4 speakers with a nominal impedance of 8 Ohms each to one channel
of of your amplifier, collectively, they will have an nominal
impedance load of 2Ohms, which is beyond the range of most domestic
amps. However if it is capable of driving this load comfortably,
the amp will deliver a much higher wattage than it would to an
8Ohm load. However finally, this must be qualified by reminding
readers that nominal impedance is merely an average (see above),
so some "margin of error" is required when matching
speakers with an amp which may be operating at the limits of its
impedance "envelope". So as they used to say in a famous
TV cop programme "be careful out there!"
Infrasonic: - Sound frequencies which are below the lowest
frequency of human hearing (20 Hz). See also
Ultrasonic.
Insert Point: - A connection which permits the insertion
of an external signal
processing device (reverb, compressor, gate, eq etc) into
the signal chain
/ path.
Insulator: - Any material which is very poor at conducting
an electrical current (eg rubber, plastics
etc). Opposite of "conductor". See
also resistance.
Integrated Circuit (IC): - Originally
conceived by UK Ministry of Defence scientist, Geoffrey Dummer
an integrated circuit is a series of transistors
(along with capacitors, resistors
etc), working together to perform some task within one discrete
unit. The first working model of an IC was patented by Jack Kilby
of Texas Instruments as a "Solid Circuit" using Germanium
as a semiconductor.
Slightly later (1961), a more advanced device, utilzing silicon
as the semiconductive material, and known at the time as a "Unitary
Circuit" (Later "Integrated"), was patented by
Kenneth (Intel) Noyce when he was working at Fairchild Semiconductor.
Intel's Ted Hoff later took IC's to an extreme, when he developed
a device known as a "microprocessor",
(the Intel 4044).
"IPS": - Acronym of Inches Per Second, a measurement
of the speed that a tape travels when it is playing.
"IRQ" (Interrupt request): - An Interrupt Request
is a message, usually sent from a hardware device within/ connected
to your computer (eg Hard Disk, printer etc) via a dedicated line
to the Central Processing Unit (CPU) of your system. In modern
"plug and play" systems each dedicated IRQ line is automatically
assigned a number, however in older systems this had to be set
manually by the user. IBM standard PC's have a maximum of 15 IRQ
lines, which work on a priority basis, depending on the relative
importance of the Interrupt. so that an Interrupt Request with
a high priority may interrupt one with a lower priority, and one
with a very high priority may override both of them! For reference,
heres a list (below) of the standard IRQ configuration for a PC
standard computer.
00) - System Timer . . . 01) - Keyboard . . . 02)
- Cascade Controller / 2nd PIC . . . 03) - COM's 2 &
4 . . . 04) - COM's 1 & 4 . . . 05) - Sound
/ Parallel Port 2 . . . 06) - Floppy Disk . . . 07)
- Parallel Port 1 . . . 08) - Real Time Clock . . . 09)
- Redirected IRQ2 / Network Available / Open . . . 10)
- Open . . . 11) - SCSI / Video / Open . . . 12)
- PS2 / Open . . . 13) - Co Processor . . . 14)
- Primary Hard Disk (Master) / Hard Disk Controller / Open . .
. 15) - Secondary Hard Disk (Slave) / Open .
It should be noted that IRQ's 00, 01, 02, 08 and 13 Should always
remain static, and never be removed or shared with any other devices,
whereas the others may possibly be reconfigured or removed.
Isopropyl Alcohol: - Best kind of alcohol to use for the
cleaning of tape heads and other metallic devices used in audio.
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"Jack" plug: - Very popular form of audio connector,
available in stereo or mono formats. A full sized Jack plug has
a spur of a quarter of an inch, but there are also smaller "mini"
jack plugs.
Jitter: - A form of digital distortion
caused by a very slight imprecision of digital sampling times
(when sound is recoded digitally, it is done by "slicing"
the signal into many segments, see Sample
for a further explaination), leading to amplitude (signal level)
errors. The distortion is more pronounced at the higher end of
the frequency spectrum. Jitter also refers
to timing errors where the word
clock is an embedded part of the datastream (self-clocking).
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k: - Prefix, an abbreviation of kilo or 1000, eg kiloHertz
/ kHz - 1000 Hertz, kiloByte / kB - 1000 bytes (oop's! sorry,
that one's 1024 but you know what I mean!).
Key: - Foundation of all tonal music, a dominant note or chord of a piece of music,
dominant major or minor scale used to construct melodies and harmonies in a piece of music.
For example, a piece in the key of C major uses mostly notes of the C major scale. A piece of music can
have several key changes in it, and this is known as "modulation" (see "key change" below).
The first note of a scale is known as the tonic and is the note that tells us the name of the key.
Key Signiture: - Usually found at the start of a musical manuscript, just after the clef.
Saves the musician the bother of writing sharps or flats on every "accidental" note within the piece, and saves cluttering up the stave. If there are no symbols, then the piece will be in the key of C Major or A Minor, or it could possibly be a piece of arty "atonal" music by Karlheinz Stockhausen or someone similar, which has no key.
Key Change: Also known as "modulation".
Keygrouping: - see Sample
(Multisampling).
Keying Input / Keying Signal: - A Keying Signal
is an electronic signal sent to the Keying Input of an electronic
musical or signal
processing device which acts as a "trigger" to activate
it.
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LFO: - Acronym of Low Frequency Oscillator,
or Low Frequency Oscillations. see also Synthesiser
(*Oscillator) .
Limiter: - Signal processing which sharply cuts off output
once it reaches a certain preset level. Roughly it is a form of
compression (see dynamics processing) with
a very high ratio (10/1 or over) used mostly for for the protection
of ears loudspeakers etc.
Line level signal: - For an audio device which uses unbalanced
inputs / outputs, a line level signal is a signal with a level
of -10dBV (0.316 volt).
for a device which uses balanced inputs /
outputs, it is a signal whose level is at +4dBm (1.23 volts).
Load (Computing): - Copy data from persistent storage
(Hard Disk, Floppy etc) into RAM memory.
Load / Load Impedance: - Electronically,
a load is burden placed in terms of resistance
to the signal from an electronic circuit (eg
loudspeaker / crossover from another circuit which is supplying
the power (eg amp). The impedance is the measurement of this resistance
in terms of Ohms.
Loop: - At its most basic, a loop is a series of instructions
(computing) or beats / notes / chords (music) that is capable
of constant repetition, consistently having the same result. Musically
this will usually be a short piece measured in terms of a bar
or more, which will seamlessly repeat without any musical / tempo
inconsistencies, annoying clicks etc.
Low Pass Filter / LPF: - A filter
which attenuates frequencies which are above
it's stated cutoff frequency. See also "Crossover".
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Machine Head: - The part of a guitar, usually situated
at the top of the neck, which contains the tuning mechanisms for
each string.
Major (music): - See Scale (Diatonic).
Master: - A device which controls another device, known
as the slave.
The final mix of a piece of music.
Microprocessor / CPU (Central Processing Unit): - Complex
Integrated Circuit which is capable of performing
some kind of computation / routine.
The three most important parts of a microprocessor are
a) it's Instruction Set (the instructions that
the processor can execute).
b) It's Bandwidth (the number of bits
it can process in a single instruction eg 8, 16, 32, 64 bit etc),
and
c) It's Clock Speed, which is the amount of instructions
that the processor can execute within one second. Hence, a 3GHz,
32 bit microprocessor can execute 3 billion cycles of 32 bits
per second.
(Gordon) Moore's Law (also Intel) says roughly that an IC / microprocessor
manufacturer will be able to place twice as many transistors
into the same area of a microprocessor every eighteen months,
with a coresponding increase in speed. Hence, if a companies fastest
microprocessor clockspeed is say, 3.5 GHz, in eighteen months
time it will be probably be around 7 GHz.
Microphone: - Electro-acoustic device which can pickup
soundwaves
and convert them into an electronic signal. See also Condenser
Microphone, Dynamic Microphone, Polar
Pattern etc
"MIDI": - Musical Instrument
Digital Interface "protocol" launched
1982 which allowed electronic instruments to "talk"
with each other digitally through three standardised ports which
utilised the existing "DIN" standard connector: A network
of musical instruments / effects etc may be created provided each
instrument is compatible with this protocol. The ports are...
1) MIDI IN - Receives MIDI information from another device.
2) MIDI OUT - Transmits MIDI information to another device.
3) MIDI THRU - Allows data to pass through unaltered, which enables
many instruments to be connected in series.
(see also "M.I.D.I. sequencing").
"General" MIDI (GM): - Standard set of sounds
for use within MIDI system (MIDI keyboards MIDI compatable soundcards
etc) which are designed to ensure compatibility for the playback
of MIDI files. A sound set of 128 sounds is the standard.
"GS MIDI": - An extension to the General MIDI
system (see above) created by the Roland corporation. Improvements
over the standard GM include reverb / chorus effects, panning
controls, and the capability of expanding the standard GM set
of 128 sounds up to a maximum of over 16,000 !
MIDI Sequencer: - a piece of digital
hardware/software that can instruct a compatible instrument to
switch notes on/off at whatever velocity they were "recorded"
at. Rather than recording sound or "audio" however it
records the parameters of the note. The sounds triggered are dependent
on the MIDI instrument or sampler supplying the sound. There are
up to 16 channels per MIDI loop operating within increments of
0 - 127. M.I.D.I. instructions (e.g. turn note off, velocity etc),
are known as "events".
MIDI + Audio Sequencer: - software running on modern microcomputers
that takes advantage of modern processing power/storage capacity
to run sequences of digitally recorded audio alongside the M.I.D.I.
messages mentioned above.
XG (MIDI) : - An extension to the General MIDI system
(see above) similar the Roland "GS" system with extra
sounds, effects etc, only this system was developed by Yamaha,
rather than Roland.
Minor (music): - See Scale (Diatonic).
Mixing: - Reduction and adjustment/enhancement of larger
amount of independent audio signals into a smaller amount.
Modulation: - See Key Change.
Monophonic (Instrument/Synth): - Synthesiser
(or other instrument) which is only capable of playing one note
at a time. See also polyphonic.
Multisampling: - see "Sample".
Multi Timbral: - Capability for an electronic instrument
to play more than one sound / patch at the same time. See also
Timbre
and Harmonic(s).
Multitrack Recording: - Ability to record and process
several separate streams or "tracks" of audio, either
together or at different times, to be played back as a synchronous
whole, then probably "mixed down" to a stereo (two track)
master for replay on ordinary systems.
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