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Dictionary of Audio Terminology - G

G The symbol for conductance.

gack – (1) To pretend to play a musical instrument, especially guitar. (2). An excessive or disordered collection of miscellaneous gear.

gadulka - A Bulgarian bowed stringed instrument.

gagaku - A type of Japanese music.

gaida (also gajda) - A form of Balkan bagpipe with the bag made from the whole skin of a goat or lamb, sometimes with the wool still left on so it looks like the player is squeezing a lamb under their arm.

gain - The amount of amplification (voltage, current or power) of an audio signal, usually express in units of dB (i.e., the ratio of the output level to the input level).

gain bandwidth product ((GBW) or gain bandwidth) - (aka unity gain bandwidth) - Alternate specification for the unity gain frequency of the device. An op amp's frequency vs. gain response rolls off at a 20 dB/decade (6 dB/octave) rate. Because of this the unity gain bandwidth specification (the frequency where the open loop gain is one or unity) also equals the gain bandwidth product.

gain-sharing - A shortened form meaning a gain-sharing algorithm. Using a gain-sharing algorithm, each individual microphone input channel is attenuated by an amount, in dB, equal to the difference, in dB, between that channel’s level and the level of the sum of all channels.

gain stage - Any of several points in an electrical circuit where gain is taken (applied).

gain suppression or suppression - In teleconferencing the term used to describe the technique of instantaneous reduction of a sound system's overall gain to control acoustic feedback and thus reduce echoes.

GAL® (generic array logic) - Registered trademark of Lattice Semiconductor for their invention of EEPROM-based low-power programmable logic devices.

Galois field (aka finite field) (after French mathematician Évariste Galois) – In reference to mathematics, a field with a finite number of elements.

galvanic - Of or relating to direct-current electricity, especially when produced chemically. [AHD]

galvanic isolation Electronics. Prevention of electrical current from passing between sections. Common examples are transformers and optocouplers. Any system with ground common is NOT galvanically isolated.

gang, ganged, ganging - To couple two or more controls (analog or digital) mechanically (or electronically) so that operating one automatically operates the other, usually applied to potentiometers (pots). The volume control in a traditional two-channel hi-fi system is an example of a ganged control, where it is desired to change the gain of two channels by the same amount, and now in home theater and DVD-audio applications, used to change 6 or more channels simultaneously.

Gaohu - Chinese bowed string instrument.

gap - The space between opposite poles of a recording or playback head in a magnetic tape recorder.

gap detection threshold - Measure of the shortest interruption of a signal that can be detected by a listener. [Lass & Woodford]

gated or gated-on - In reference to teleconferencing, a term referring to microphone inputs on an automatic mic mixer that turn off (close) after speech stops.

gauge - A measure of the diameter of wire.

gauss Abbr. Gs The centimeter-gram-second unit of magnetic flux density, equal to one Maxwell (one line of flux) per square centimeter. [AHD]

Gauss, Karl Friedrich (b. 1777-1855). German mathematician and astronomer known for his contributions to algebra, differential geometry, probability theory, and number theory. [AHD]

Gaussian distribution - Same as normal distribution. A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve symmetrical about the mean. [AHD]

GBW (gain bandwidth or gain bandwidth product) (aka unity gain bandwidth) - Alternate specification for the unity gain frequency of the device. An op amp's frequency vs. gain response rolls off at a 20 dB/decade (6 dB/octave) rate. Because of this the unity gain bandwidth specification (the frequency where the open loop gain is one or unity) also equals the gain bandwidth product.

G clef or treble clef - A symbol indicating that the second line from the bottom of a staff represents the pitch of G above middle C. [AHD]

GE (gigabit Ethernet) - In computer networking, Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second (1,000,000,000 bits per second), as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed considerably faster. The cables and equipment are very similar to previous standards, and as of 2011 are very common and economical. [Wikipedia]

geometric progression - A sequence, such as the numbers 1, 3, 9, 27, 81, in which each term is multiplied by the same factor in order to obtain the following term. Also called geometric sequence. [AHD]

Gerzon, Michael - (b. 1945-1996) British mathematician considered one of the true geniuses of the twentieth century. Made many pro audio inventions the most famous of which is Ambisonics and the theory behind the tetrahedron microphone.

getter - A small amount of material added to a chemical or metallurgical process to absorb impurities. In vacuum tubes it is a small cup or holder, containing a bit of a metal that reacts with oxygen strongly and absorbs it. In most modern glass tubes, the getter metal is barium, which oxidizes very easily forming white barium oxide. This oxidization removes any oxygen remaining after vacuumization.

Gibbs phenomenon - The ringing and overshoot that can occur when constructing a waveform by adding together harmonics and abruptly stopping the harmonic series after a finite number of terms. [Greenebaum]

gibi Symbol Gi New term standardized by the IEC as Amendment 2 to IEC 60027-2 Letter Symbols to be Used in Electrical Technology to signify binary multiples of 1,073,741,824 (i.e., 2E30). Meant to distinguish between exact binary and decimal quantities, i.e., 1,073,741,824 verses 1,000,000,000. For example, it is now 16 gibibits, abbreviated 16 Gib, not 16 gigabits or 16 Gb.

giga - A prefix signifying one billion (10E9), abbreviated G.

gigabyte - Popular term meaning a billion bytes but should be gibibyte meaning 2E30 bytes.

GIGO (garbage in garbage out) - Popular acronym used by programmers to indicate that incorrect information sent to a system generally results in incorrect information received from it.

gigue or jig - Any of various lively dances in triple time. The music for such a dance.

glass - Popular jargon referring to glass fiber optic interconnection, or fiber optics in general.

glass harmonic or glass harmonica - A musical instrument comprising separate glasses, playing the rims, or a long tapered cylinder rotating and played by hand. First mentioned in the early 1740s and later improved by Benjamin Franklin in 1761.

glide or portamento - A smooth uninterrupted glide in passing from one tone to another, especially with the voice or a bowed stringed instrument.

glissando - A rapid slide through a series of consecutive tones in a scale-like passage. [AHD]

glitch - A perturbation of the pulse waveform of relatively short duration and of uncertain origin. [IEEE] (1) A minor malfunction, mishap, or technical problem; a snag: a computer glitch; a navigational glitch; a glitch in the negotiations. (2) A false or spurious electronic signal caused by a brief, unwanted surge of electric power. [AHD] glitch edit - A popular remixing effect.

glockenspiel - A percussion instrument with a series of metal bars tuned to the chromatic scale and played with two light hammers. [AHD]

glottis - (1) The opening between the vocal cords at the upper part of the larynx. (2) The vocal apparatus of the larynx. [AHD]

GMT (Greenwich Mean Time) - The mean solar time for the meridian at Greenwich, England, used as a basis for calculating time throughout most of the world.

GND (ground) - Common abbreviation seen on electronic and electrical schematic diagrams.

gobble pipe - Saxophone. [Decharne]

goblet drum (aka Chalice drum, Darbuka or Doumbek) - A wine glass shaped hand drum indiginous to the Middle East.

gobo – (1) In reference to cinematography & photography, a portable screen used to shield a camera lens from light or a microphone from noise. (2) In reference to acoustics & recording, a sound absorbent screen used to isolate instruments during multitrack recording, minimizing microphone crosstalk.

Golden Ratio or Golden Rectangle or phi - It is a never-ending, never-repeating number found by calculating this formula:

Golliwogs - The original name of the band that evolved into Creedence Clearwater Revival.

GOTS (government off-the-shelf) - Government procurement term. Most often referencing software but general use is found. Compare with COTS, MOTS and NOTS.

GPI - General purpose interface

GPIB (general purpose interface bus) or IEEE-488 - The most common parallel format computer interface for simultaneous control of up to 15 multiple peripherals.

gradient microphone - A pressure-gradient microphone uses a diaphragm that is at least partially open on both sides. The pressure difference between the two sides produces its directional characteristics. Other elements such as the external shape of the microphone and external devices such as interference tubes can also alter a microphone's directional response. A pure pressure-gradient microphone is equally sensitive to sounds arriving from front or back, but insensitive to sounds arriving from the side because sound arriving at the front and back at the same time creates no gradient between the two. The characteristic directional pattern of a pure pressure-gradient microphone is like a figure-8.

gram Abbr. g or gm. or gr. A metric unit of mass equal to one thousandth (10-3) of a kilogram. [AHD]

gramophone - British term referring to any sound reproducing machine using disc records, as disc records were popularized in the UK by the Gramophone Company. Invented by Emil Berliner.

Grammy - Shorten form of gramophone, name of the Grammy Awards given by The Recording Academy.

granulation noise - An audible distortion resulting from quantization error.

graphene - A one-atom-thick sheet of pure carbon which won the 2010 Nobel Prize for Physics; among many different things it is experimentally producing silicon-less transistors.

graphic equalizer - A multi-band variable equalizer using front panel mechanical slide controls as the amplitude adjustable elements. Named for the positions of the sliders "graphing" the resulting frequency response of the equalizer. Only found on active designs. Center frequency and bandwidth are fixed for each band.

Grashof, Nusselt and Prandtl numbers - In reference to Thermodynamics, all are found in the study of natural convection as occurs, for example, from heat sinks in audio power amplifiers:

Grashof (Gr), is the ratio of buoyant force to viscous force; Nusselt (Nu) is the coefficient of heat transfer; and Prandtl (Pr) is the ratio of the molecular diffusion coefficients of momentum in terms of heat, i.e., a property of air. And for those who love a good formula, this is the correlation for natural convection from a flat plate.

Nu - Equal to 0.59 (Gr Pr)0.25 [Kordyban]

gray code - A sequence of binary values where only one bit is allowed to change between successive values. Generally "quieter" (producing less audible interference) than straight binary coding for execution of commands in audio systems.

Gray, Elisha - (b. 1835-1901) American electrical engineer who invented the Musical Telegraph after developing the first telephone, more or less simultaneously with Alexander Graham Bell.

Gray, Stephen - (b. 1666-1736) British chemist who is credited with the discovery of electrical conduction and insulation.

Green Book - Nickname for the Philips and Sony's ECMA-130 standard document that defines the format for CD-I (compact disc-interactive) discs; available only to licensees. Compare with Red Book and Yellow Book.

Greenwich time - The mean solar time for the meridian at Greenwich, England, used as a basis for calculating time throughout most of the world. Also called Greenwich Mean Time, Zulu time. [AHD]

greenockite - A yellow to brown or red mineral, CdS, the only ore of cadmium. [After Charles Murray Cathcart, Second Earl Greenock (1783-1859), British soldier.]

grid - The current controlling element in a tube located between the plate and the cathode. It is equivalent to the base in a transistor. A triode tube consists of a plate, cathode and grid, which are directly analogous to the collector, emitter and base of a transistor.

grille - (1) A grating of metal, wood, or another material used as a screen, divider, barrier, or decorative element, as in a window or on the front end of an automotive vehicle. (2) An opening covered with a grating. [AHD]

grille cloth - A tough acoustically transparent cloth (or metal) put over the front of a loudspeaker to protect the speaker from damage.

groan box - Accordion. [Decharne]

ground - The common reference point for electrical circuits; the return path; the point of zero potential.

ground lift switch – (1) Found on the rear of many pro audio products, used to separate (lift) the signal ground and the chassis ground connection. (2) Common three-pin to two-pin AC plug adapter used to reduce ground loops. [NOTE: This is unsafe and illegal. DO NOT USE.]

ground loop – (1) In reference to electronics, within a single circuit, or an audio system, the condition resulting from multiple ground paths of different lengths and impedances producing voltage drops between paths or units. A voltage difference developed between separate grounding paths due to unequal impedance such that two "ground points" actually measure distinct and different voltage potentials relative to the power supply ground reference point. (2) In reference to aviation, the tendency of a tailwheel aircraft (vs. tricycle gear) to pivot around its vertical axis during runway operations in the presence of a high crosswind.

groups (aka subgroup or submix) - A combination of two or more signal channels gathered together and treated as a set that can be varied in overall level from a single control or set of controls. Mixing consoles often provide a group function mode, where the level of any group of incoming singles may be adjusted by a single slide fader, which is designated as the group fader. Likewise in certain signal processing equipment with splitting and routing capabilities, you will have the ability to group together, or assign, outputs allowing control of the overall level by a single external controller.

group delay or envelope delay - [technically the time interval required for the crest of a group of waves to travel through a 2-port network -IEEE.] The rate of change of phase shift with respect to frequency. Mathematically, the first derivative of phase verses frequency. The rate of change is just a measure of the slope of the phase shift verses linear (not log) frequency plot. If this plot is a straight line, it is said to have a "constant" (i.e., not changing) phase shift, or a "linear phase" (or "phase linear" -European) characteristic. Hence, constant group delay, or linear group delay, describes circuits or systems exhibiting constant delay for all frequencies, i.e., all frequencies experience the same delay. Note that pure signal delay causes a phase shift proportional to frequency, and is said to be "linear phase," or "phase linear." In acoustics, such a system is commonly referred to as a "minimum phase" system.

GR plug or banana jack or banana plug - A single conductor electrical connector with a banana-shaped spring-metal tip most often used on audio power amplifiers for the loudspeaker wiring. Usually configured as a color-coded molded pair (red = hot & black = return) on 3/4" spacing. Also used for test leads and as terminals for plug-in components. The British still refer to these as a GR plug, after General Radio Corporation, the inventor (according to The Audio Dictionary by Glenn D. White).

grunge (aka Seattle sound) - A style of rock music that incorporates elements of punk rock and heavy metal, popularized in the early 1990s and often marked by lyrics exhibiting nihilism, dissatisfaction, or apathy. [AHD]

GUI (graphical user interface) - A generic name for any computer interface that substitutes graphics (like buttons, arrows, switches, sliders, etc.) for characters; usually operated by a mouse or trackball. First mass use was Apple's Macintosh™ computers, but is now dominated by Microsoft's Windows™ programs.

gumbo ya-ya - New Orleans slang for everybody talking at once.

guqin or qin - A Chinese musical instrument dating from 1000 BC similar to a zither; common name for most Chinese stringed instruments.

guitarron - A six string bass instrument most popular among Mariachi groups, but found throughout Argentina, Chile, Mexico and Puerto Rico.

gut scraper - Violinist. [Decharne]

Gutta-percha - A type of iInsulation used for early wire cables.

gyrator filters - Term used to describe a class of active filters using gyrator networks. Gyrator is the name given for RC networks that mimic inductors. A gyrator is a form of artificial inductor where an RC filter synthesizes inductive characteristics. Used to replace real inductors in filter design.

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