q (lower-case) - The symbol for charge.
Q (upper-case) - In reference to filters, the selectivity factor defined to be the ratio of the center frequency f divided by the bandwidth "BW".
Q (upper-case) - In reference to loud-speakers, used to connote the directivity, or a measure of the directional characteristic of a loudspeaker, and is called the Directivity Index, either measured in decibels, or as a dimensionless value of Q.
Q-8 - RCA's name for their 4-channel, eight-track tape cartridges, the world's first (and last).
qanbus - A short-necked fretless flute indigenous to Yemen.
QD LED (quantum-dot LED) - Latest LED technology based on quantum dot semiconductor nanocrystals.
QED (Quod erat demonstrandum) - Literally, "which was to be demonstrated." Used to connote the end of a mathematical proof.
qin (also guqin) - A Chinese musical instrument similar to a zither; common name for most Chinese stringed instruments.
QoS (quality of service) - Today's usage: "Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow." [From Wikipedia] Original usage: (1) The performance specification of a communications channel or system. It may be quantitatively indicated by channel or system performance parameters, such as signal-to-noise ratio (S/N), bit error ratio (BER), message throughput rate, and call blocking probability. (2) A subjective rating of telephone communications quality in which listeners judge transmissions by qualifiers, such as excellent, good, fair, poor, or unsatisfactory. [From Federal Standard 1037C].
QR code (Quick Response code) - A matrix barcode readable by devices with cameras, i.e., smart phones, tablets, etc.
QRD (quadratic residue diffusor) - Another name for a Schroeder diffusor.
QS - Sansui's name for their quadraphonic sound system using a proprietary matrixing algorithm for encoding four-channel sound down to two-channels. Compare with SQ.
QSound - The name of a Canadian company and its proprietary and patented 3D sound technology.
QTC (quantum tunnelling composite) - Pressure sensors based on quantum physics.
quackery - The statement floating about cyberspace that a duck's quack does not echo and no one knows why.
quad flat pack - The most commonly used package in surface mount technology to achieve a high lead count in a small area. Leads are brought out on all four sides of a thin square package.
quad mic cable - A four-conductor cable exhibiting very low noise and hum pickup (hum reduction can be 30 dB better than standard mic cable). The four conductors are wound together in a spiral, and then opposite conductors are joined together at the connectors forming a two-conductor balanced line (also called double balanced) with superior performance.
Quadradisc (Compatible Discrete 4) also called (Quadradisc) - JVC introduced this discrete quadraphonic vinyl record in 1971. This was the only successful discrete 4-channel record, although short lived.
quadraphonic sound - Coined in the '70s, the original term for surround sound.
quadratic equation - An equation in which one or more of the terms is squared but raised to no higher power, having the general form ax² + bx + c = 0, where a, b, and c are constants.
quadratic residue diffuser - A type of Schroeder diffuser consisting of a plane surface with an array of parallel slots all the same width but with varying depths based on a prime number mathematical sequence.
quadrature - A state of separation or relationship equal to 90°. For example, two same frequency sine waves one-quarter wavelength apart are in quadrature. A phase difference equal to one-fourth of a period.
quadrupole sound source - Quadrupole is defined as a multipole of order two, therefore two opposite dipoles make up a quadrupole source.
Quanoon - Egyptian dulcimer. Contrast with: Qanoun.
quantization distortion - Same as quantization error.
quantization error - Error resulting from quantizing an analog waveform to a discrete level. It is the difference between the actual value of the analog signal at the sampling instant and the nearest quantization value. Therefore, in general, the longer the word length, the less the error, because there are more step sizes to choose the closest.
quantization - The process of converting, or digitizing, the almost infinitely variable amplitude of an analog waveform to one of a finite series of discrete levels. Performed by the A/D converter.
quantum - The smallest amount of a physical quantity that can exist independently, especially a discrete quantity of electromagnetic radiation.
quantum dot - A confined and isolated atom such that the removal or addition of a single electron can be detected, i.e., its properties change in a detectable manner -- the ultimate memory cell. In nanotechnology, they are called quantum bits or qubits.
quantum entanglement - occurs when particles such as photons, electrons, molecules as large as "buckyballs", and even small diamonds interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description (state), which is indefinite in terms of important factors such as position, momentum, spin, polarization, etc. [Wikipedia]
quantum noise - Any noise attributable to the discrete nature of electromagnetic radiation.
quantum tunneling composite (QTC) - Pressure sensors based on quantum physics.
quarter-inch jack - Same as 1/4" TRS or 1/4" TS. (1) Stereo 1/4" connector consisting of tip (T), ring (R), and sleeve (S) sections, with T = left, R = right, and S = ground/shield. (2) Balanced interconnect with the positive & negative signal lines tied to T and R respectively and S acting as an overall shield. (3) Insert loop interconnect with T = send, R = return, and S = ground/shield. The international standard is IEC 60603-11.
quarter-note - A note having one-fourth the time value of a whole note.
quarter-track stereo - An analog recording head arrangement that allows recording two tracks in one direction and another two tracks in the opposite direction. The name comes from each track and guard band using one quarter of the tape width.
quartet - (1) A group of four adjacent digits operated upon as a unit. (2) A byte composed of four bits, i.e., a nibble.
quartz crystals - A small crystal of quartz accurately cut along certain axes so that it can be vibrated at a particular frequency, used for its piezoelectric properties to produce an electric signal of constant known frequency.
quasi - To some degree; in some manner.
quasi-balanced line - A quasi-balanced output stage consisting of an unbalanced output connected to the tip of a ¼" TRS (tip-ring-sleeve) jack through an output resistor (typically in the 50-300 ohms range). An equal valued resistor is used to tie the ring terminal to signal ground. The sleeve connection is left open or "floating." Thus, from the receiver's viewpoint, what is "seen" are two lines of equal impedance, used to transfer the signal. In this sense, the line is 'balanced," although only one line is actually being driven.
quasi-parametric - parametric equalizers which allow control of center frequency but not bandwidth with rotary controls.
quasi-peak detector - A detector having specified electrical time constants that, when regularly repeated pulses of constant amplitude are applied to it, delivers an output voltage that is a fraction of the peak value of the pulses, the fraction increasing toward unity as the pulse repetition rate is increased. [IEEE]
quaternary - The word that comes after primary, secondary, tertiary.
qubits - quantum dot.
Queen, Daniel - (b. 1934-2002) Long-time Standards Manager for the AES, Daniel had a full and productive audio career including his successful consulting company, Daniel Queen Associates, specializing in electroacoustics, architectural acoustics, and noise control. He joined the AES in 1962 and became a fellow in 1970.
quena (also called a kena) - A shepard's pipe, or flute) without a mouthpiece.
quiescent - Being quiet, still, or at rest; inactive. [AHD]
quiescent noise - Another name for a product's residual noise or noise floor.
quieting sensitivity (Also called IHF Sensitivity) - The minimum input signal required to provide a distortion-free listenable output signal."The minimum unmodulated signal input for which the output signal-to-noise ratio does not exceed a specified limit, under specified conditions." [IEEE]
quinary - The word that comes after primary, secondary, tertiary, quaternary.
Quinnipiac (pronounced KWIN-uh-pe-ack) - A private, coeducational, nonsectarian university located in Hamden, CT, featuring a fully digital high-definition broadcast studio.
quint - Name for an interval of a fifth.
quintephone - A musical instrument that generates sound "informatically," i.e., using information science and technology.
quinton - A 17th-centruy treble viol. Also, an 18th-century five-stringed hybrid between the viol and violin families.
quintophonic sound (also seen as quintaphonic sound) - The name of the 5-channel discrete surround system developed by John Mosely for The Who's rock opera, Tommy, production. The forerunner of 5.1 surround systems.
quitiplas - A Venezuelan bamboo instrument.
quother - To talk in a low and confidential tone. [Kacirk]
quotient - The number obtained by dividing one quantity by another. In 45 ÷ 3 = 15, 15 is the quotient. [AHD]
QWERTY - Nickname for the computer (or typewriter) keyboard derived from the left side, top row of letter keys.
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