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synthesis glossary
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Photon



Joined: Mar 22, 2005
Posts: 363
Location: Boston
Audio files: 1

PostPosted: Sun May 27, 2007 10:51 am    Post subject:  synthesis glossary Reply with quote  Mark this post and the followings unread

Here's a glossary that I've started to put together from varied sources. I thought it may be helpful to post it here. If anyone finds any errors or has additions or corrections please PM me and I'll add it. I'll be updating this as I have time. Any suggestions are welcome.

Peter

Last edited by Photon on Sun May 27, 2007 10:55 am; edited 1 time in total
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Photon



Joined: Mar 22, 2005
Posts: 363
Location: Boston
Audio files: 1

PostPosted: Sun May 27, 2007 10:51 am    Post subject: Reply with quote  Mark this post and the followings unread

AC: Electricity of which varies periodically about some reference level.

Additive synthesis: The process of combining simple waveshapes to create new, more complex waveshapes

ADSR generator: An envelope generator with at least four controls- Attack time / initial Decay time / Sustain level / final Release time

Amplifier, voltage controlled: An amplifier, the gain of which is a function of the voltage applied to its control input

Amplitude: The maximum absolute value reached by a voltage or current waveform (during one wave cycle)

Amplitude modulation: The process of periodically modulating the gain of an amplifier

Analog: A continuously variable signal, rather than one composed of discrete steps, as with a digital signal

Attenuation: Reduction in signal amplitude

AR generator: An envelope generator with controls for setting the attack and release times

Attack: The time it takes a signal to build up from its minimum to its maximum level

Audio frequency range: The range of frequencies that are perceived as sound, typically considered to be about 20 Hz to 20 kHz


Balanced modulator: An amplitude modulator such that the carrier signal does not appear in the output of the device.

Band-pass filter: A filter that passes frequencies above and below its lower and upper cutoff points, respectively, while attenuating all other frequencies

Band-reject filter: A filter that attenuates frequencies above and below its lower and upper cutoff points while passing all other frequencies

Bias: A signal applied to a device to establish an operating point

Buffer: A circuit or component that is used to isolate one circuit from another

Bus: A conductor used for the distribution of signals to several destinations

Center frequency: the mid-point of a band-pass filter's passband

Clipping: A type of distortion produced as a result of a device being operated in a nonlinear amplitude region

Comparator: A circuit used to compare the amplitude of an input signal with a reference voltage. the output of the comparator changes from logical 0 (output of the comparator full off) to logical 1 (output of the comparator full on), and vice versa

Control Voltage: An electrical signal used to control the action of an electronic circuit

Crosstalk: A measure of the interference between two signal paths caused by stray electromagnetic or electrostatic coupling

Cutoff frequency: The nominal endpoint of a filter's passband

DC: An unchanging signal. A steady, unchanging voltage or current


Decay: The time it takes a signal to drop from a maximum to a minimum level

Demodulation: Recovery of the modulating (program) signal from the modulated signal

Distortion: Any alteration in a given waveform. Harmonic distortion produces new frequency components which are integrally related to the frequency components of the original signal. Heterodyne Distortion produces new frequency components that correspond to the sums and differences of the fundamentals and harmonics of two or more frequencies

Doppler effect: An apparent frequency shift due to relative motion between source and listener

Duty cycle: The ratio of high-amplitude time to total cycle time in a rectangle wave. ie. the duty cycle of a square wave is 1:2

Dynamic range: Ratio of maximum signal level ( for a given distortion) to minimum signal level which can be processed by a system. Usually measured in decibels.

Envelope: a curve drawn through the points of maximum positive and/or negative excursion of a signal

Envelope follower: A device consisting basically of a rectifier and low-pass filter which produces an output voltage proportional to the amplitude of the input signal

Exponential: A change that progresses faster at one extreme of its range. If graphed linearly, the graph would be a curve

Feedback: The application of some proportion of the output signal of a device back to the input of the device

Floating: Having no established reference potential (including ground)

Formant: An emphasized portion of the audible spectrum characteristic of a specific timbre or voice

Fundamental: The predominant (and usually lowest) frequency in a complex signal. The perceived pitch

Gain: The ratio of the voltage, power, or current at the output of a device. Gain is often expressed in dB.

Gate: Any device used to control the amplitude-versus-time characteristics of a signal

Ground: That point in a circuit used as a reference point in voltage measurements; The conductive chassis on which a circuit is connected; The earth or low-resistance conductor connected to the earth

Ground loop: The generation of spurious signals in a ground conductor, usually resulting from the connection of two separate grounds to a signal circuit

Harmonic: An overtone that is an exact integer ( whole number) multiple of the fundamental

Heterodyning: The mixing (non-linear) of two signals so as to produce new frequency components equal to the sum and difference of the frequencies of the two signals

High-pass filter: A filter that passes signals of frequency greater than its cutoff frequency and attenuates signals of frequency less than its cutoff frequency

Impedance: The total AC resistance of circuit

Inverting amplifier: An amplifier which multiplies the input signal by -A, where A is the voltage gain of the amplifier

Linearity: The property that the output resulting from the sum of two inputs is the sum of the outputs which would result from each output alone

Low-pass filter: A filter that passes signals of frequency less than its cutoff frequency and attenuates signals of frequency greater than its cutoff frequency

Mixer: A device used to produce the algebraic summation of two or more signals

Modulation: A process by which a characteristic or characteristics (amplitude, frequency, phase) of a signal (called the carrier) is (are) varied according to changes in a characteristic or characteristics of another signal

Non-linear: having an output which does not vary in direct proportion to the input

Notch filter: A band-reject filter which is designed to attenuate a single, narrow band of frequencies

Offset voltage: The DC potential remaining across the inputs of a differential amplifier when the input signals are adjusted so that the output level is zero

Output impedance: the impedance presented by a device to a load

Patching: a temporary connection made between two lines or circuits with a patch cord

Period: The time required for a complete single oscillation or cycle of events. Period is the reciprocal of frequency.

Phase: In a periodic wave, the fraction of the period that has elapsed, measured from some fixed origin. The time required for one period is represented as 360 degrees along a time axis, the phase position is called the phase angle

Pink Noise: Weighted white noise with emphasis on the low frequencies so there is equal average energy per octave

Pulse: a brief, sudden change in signal level

Pulse width modulation: Modulating the duty cycle of a rectangle wave

Quantization: A process in which a (continuous) function is transformed into a series of discrete values

Rectangle wave: A periodic signal that switches quickly between two stable states. Sometimes called a pulse wave.

Resonant frequency: The frequency at which a peak filter exhibits maximum gain

Ring modulator: A type of balanced modulator, so named because it employs four diodes connected anode to cathode to form a ring

Roll off: An increase in attenuation over a given frequency range

Sample and hold: A circuit which when triggered samples the instantaneous level of an output signal and holds that level at the output until the next trigger signal. used for pseudo-random effects

Sawtooth-wave: A periodic signal that contains the fundamental and all harmonics, so is excellent for subtractive synthesis. Ascending sawtooth builds up smoothly from minimum to maximum, then drops quickly to back down to start over for the next cycle. Descending sawtooth drops smoothly from maximum to minimum, then jumps quickly back up to start over for the next cycle.

Sidebands: New frequencies produced as a result of modulation

Sine-wave: A periodic signal with no harmonic content, only the fundamental. Starting at zero, it gradually increases to a maximum positive, then decays to a maximum negative, then returns to the original starting place

Slew rate: The maximum rate at which the output level of a device can change from maximum to minimum

Square-wave: a special form of rectangle wave that switches between two amplitudes of equal duration. The fundamental and all harmonics are present

Triangle wave: A periodic signal where amplitude changes direction sharply at the peaks. The signal consists of a fundamental and all of the odd harmonics , with amplitudes falling off in ratios of 1/9, 1/25, 1/49, etc

Waveform: The amplitude-versus-time function of a signal

White noise: A more or less random signal in which all audible frequencies are equally likely to occur at any given instant

Zero level: A reference level used for comparing sound or signal intensities
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