P2C2E (process too complex to explain) [Thanks, Lou!]
P2P See peer-to-peer.
p The symbol for pico-.
p's and q's From old British saying: pints and quarts [... and you know pints and quarts of what.] 1. Socially correct behavior; manners. 2. The way one acts; conduct: was told to watch his p's and q's or he would be fired. [AHD]
PA-232 An RS-232-based variant of the PA-422 AES standard.
PA-422 A pro audio implementation of Electronics Industries Association EIA-422 interconnection standard, defined and adopted by the Audio Engineering Society as AES Recommended practice for sound-reinforcement systems - Communications interface (PA-422) AES 15-1991 (ANSI S4.49-1991).
PAC (Perceptual Audio Coder) Proprietary bit reduction scheme originally developed by Elemedia, a subsidiary of Bell Labs.
pad See attenuator pad.
PAE (patent assertion entities) The politically correct term for "patent trolls."
PAL® (programmable array logic) Original registered trademark of Monolithic Memories Inc. (now owned by Advanced Micro Devices, Inc.) for their fuse-link once-programmable logic parts that have a programmable AND array, but a predefined OR array. See also PLA, PLD & FPGA.
PAL/SECAM (phase alternated line/sequential couleur avec memoire or sequential color with memory) The European and Australian standard for color formatting for television transmission developed in the 1960s and used most everywhere in the world except the U.S.A. and Japan, which use NTSC.
PALM Expo (Pro Audio Lighting Music) China's Largest International Exhibition on Pro Audio, Light, Music & Technology.
PALME Conferences (Professional Audio, Light, Music and Entertainment) International exhibitions held in Middle East, Asia and Vietnam.
pan (panoramic) control A control found on mixers, used to "move," or pan the apparent position of a single sound channel between two outputs, usually "left," and "right," for stereo outputs. At one extreme of travel the sound source is heard from only one output; at the other extreme it is heard from the other output. In the middle, the sound is heard equally from each output, but is reduced in level by 3 dB relative to its original value (this is theoretical, the real world is not quite that simple -- see Pan Law). This guarantees that as the sound is panned from one side to the other, it maintains equal loudness (power) for all positions. Contrast with balance and crossfade controls.
pandemonium Loud, confused, or disagreeable sound implying disorderly tumult together with loud, bewildering sound. [AHD]
pangram A sentence that uses all the letters of the alphabet. [AHD] The most famous example comes from typing class: The quick brown fox jumps over the lazy dog.
panoply A splendid or striking array: a panoply of colorful flags. [AHD] Used in pro audio to describe loudspeaker line arrays.
Panatrope Phonographs. Designed by RCA and sold by Brunswick in 1925, this was their name for the first phonograph player to use electricity to reproduce the sound stored on the record. Hit the link to see a photo. Go to AdClassix.com to see (and buy) their original magazine advertisement.
PAQRAT® A registered trademark of Rane Corporation for their recording converter devices, RC 24T & RC 24A, that converted AES/EBU stereo 18-24 bit digital audio two track data into 16-bit compatible four tracks for recording and playback on 1st-generation 16-bit modular digital multitrack tape machines such as Alesis ADAT and Tascam DTRS (DA-88) models.
paragraphic See parametric equalizer.
parallel circuit Electronic Circuits. Two-terminal elements are connected in parallel when they are connected between the same pair of nodes. For example a parallel battery connection is made by connecting all positive terminals together and all negative terminals together, the voltage of the group being only that of one cell and the current drain through the battery being divided among the several cells. [IEEE]
parallel interface The printer port in the PC world. A parallel port conforming to the quasi-standard called the Centronics Parallel Standard (there is no EIA standard). Originally a 36-pin connector, now more often a D-25 type connector. A parallel (as opposed to serial) interface transfers all bits in a word simultaneously. See also serial interface.
parametric audio coding Audio Compression. An audio coding technology originally developed for speech. Basis of MPEG-4 standard.
parametric equalizer First designed and named by George Massenburg in 1969, a multi-band variable equalizer offering control of all the "parameters" of the internal bandpass filter sections. These parameters being amplitude, center frequency and bandwidth. This allows the user not only to control the amplitude of each band, but also to shift the center frequency and to widen or narrow the affected area. Available with rotary and slide controls. Subcategories of parametric equalizers exist which allow control of center frequency but not bandwidth. For rotary control units the most used term is quasi-parametric. For units with slide controls the popular term is paragraphic. The frequency control may be continuously variable or switch selectable in steps. Cut-only parametric equalizers (with adjustable bandwidth or not) are called notch equalizers, or band-reject equalizers. See the RaneNote Constant-Q Graphic Equalizers.
parity A redundant error detection method in which the total number of binary 1's (or 0's) is always made even or odd by appending one or more bits.
Parkinson's Law "Work expands so as to fill the time available for its completion." Prof. Cyril Northcote Parkinson (1909-1993)
partial or partial tone See harmonic.
pascal Abbr. Pa. The International System unit of pressure equal to one newton per square meter. [After Blaise Pascal.]
Pascal, Blaise (1623-1662) French philosopher and mathematician. Among his achievements are the invention of an adding machine and the development of the modern theory of probability. Famous quote: "I have made this letter longer than usual because I lack the time to make it short." - Blaise Pascal, in "Provincial Letters."
passband The range of frequencies passed by an audio low-pass, high-pass or bandpass filter. Normally measured at the -3 dB point: the frequency point where the amplitude response is attenuated 3 dB (decibels) relative to the level of the main passband. For a bandpass filter two points are referenced: the upper and lower -3 dB points. The -3 dB point represents the frequency where the output power has been reduced by one-half. [Technical details: -3 dB represents a multiplier of 0.707. If the voltage is reduced by 0.707, the current is also reduced by 0.707 (ohms law), and since power equals voltage-times-current, 0.707 times 0.707 equals 0.5, or half-power.] The opposite of stopband.
passive crossover A loudspeaker crossover not requiring a power supply for operation. Normally built into the loudspeaker cabinet. Passive crossovers do not require separate power amplifiers for each driver. See active crossover. See the RaneNote Signal Processing Fundamentals.
passive equalizer A variable equalizer requiring no power supply to operate. Consisting only of passive components (inductors, capacitors and resistors) passive equalizers have no AC line cord. Favored for their low noise performance (no active components to generate noise), high dynamic range (no active power supplies to limit voltage swing), extremely good reliability (passive components rarely break), and lack of RFI interference (no semiconductors to detect radio frequencies). Disliked for their cost (inductors are expensive), size (and bulky), weight (and heavy), hum susceptibility (and need careful shielding), and signal loss characteristic (passive equalizers always reduce the signal). Also inductors saturate easily with large low frequency signals, causing distortion. Rarely seen today, but historically they were used primarily for notching in permanent sound systems. See the RaneNote Operator Adjustable Equalizers.
PASTI (public address speech transmission index) Chiefly British term for STIpa.
patchbay or patch panel A flat panel, or enclosure, usually rack-mounted, that contains at least two rows of 1/4" TRS connectors used to "patch in" or insert into the signal path a piece of external equipment (really dense configurations use 4.4 mm miniature or "bantam" jacks). The two rows consists of "send" (top row) and "receive" (bottom row) jacks wired for true balanced interconnection, i.e., tip = positive signal, ring = negative signal, sleeve = shield ground (unbalanced patchbays exist - but should not - so no further discussion). The two rows are tied together by shorting contacts such that the normal operation (hence, "normalling" jacks) is to short the send and receive tip-to-tip & ring-to-ring (the sleeves are always connected) maintaining the signal path until something is plugged in (or jacked-in as cyberpunks love to say). Popular in recording studios where it is common to change the units in the signal path for each new session or client. Another popular wiring convention is called "half-normalled" where only one of the insert points (top: send, or bottom: receive) breaks the signal path (in normalling, or full normalling as it is sometimes called, inserting into either top or bottom row breaks the signal path). This configuration allows monitoring of the sent signal or received signal depending on which row is half-normalled. Hit the link to see diagrams.
patents See: USPTO.
patent trolls See: PAE.
Paterson, A.B. ("Banjo") (1864-1941) Australian bush poet most famous for writing the song, "Waltzing Matilda," which became Australia's unofficial national anthem. Hit the link for the fascinating story.
See for example: Jamaican Patois.
Paul, Les (1915-2009) [Birth name: Lester William Polsfuss] American musician legend who was also a gifted songwriter and inventor. His pioneering work on the solid-body electric guitar and multitrack recordings changed the pro audio industry forever.
payload See: packet.
PBX (private branch exchange) Term referring to hardware allowing several telephones to be connected to a smaller number of lines.
PC (personal computer) Original term coined by IBM to describe their first personal computers; now used to mean all IBM-compatible personal computers, or any personal computer.
PC-Card See PCMCIA.
PC-DOS® (personal computer disk operating system) IBM's trademarked acronym for their PC operating system. If PC-DOS runs on an IBM compatible, it is then called MS-DOS.
PCI (peripheral component interconnect) Intel-designed high performance CPU interconnect strategy for "glueless" I/O subsystems. A 32- or 64-bit local-bus specification, characterized by being self-configuring, open, high-bandwidth and processor-independent -- allowing for modular hardware design.
PCM (pulse code modulation) A conversion method in which digital words in a bit stream represent samples of analog information. The basis of most digital audio systems, first invented by Alec H. Reeves in 1937. Also see RaneNote: Digital Dharma of Audio A/D Converters.
PCMCIA (Personal Computer Memory Card International Association) 1. The association and first name given to the standardized credit-card size packages (aka smart cards) for memory and I/O (modems, LAN cards, etc.) for computers, laptops, palmtops, etc. Nicknamed PC-Card, which is now the preferred term. 2. Popularly believed to stand for People Can't Memorize Computer Interface Acronyms.
PDA (personal digital assistant) A small palmtop-like computer designed for specific tasks such as a pocket calculator. Other examples include personal electronic diaries, memo takers, communicators, web browsers, dictionary-translators, etc. Apple's Newton is a PDA. IBM named theirs personal communicators.
pdf (probability density function) See probability density function.
PDF files (portable document format) Suffix letters used (.pdf) to indicate an Adobe Acrobat document.
peak hold Metering. An extra function found on some LED, LCD or plasma ladder arrays where the peak value is displayed by a single element displayed above the average program material. Commonly has a slow decay rate where it is usual to see just the peak value element lit with no others once the program material ends.
peaking response Term used to describe a bandpass shape when applied to program equalization.
peak program meter See PPM.
PEAQ (perceptual evaluation of audio quality) Term for the ITU-R recommendations for the objective measurement of perceived audio quality for perceptually coded digital audio signals. Popularly called the new "electronic ear" to provide yardstick values for digitally coded audio quality, there are a series of recommendations covering various aspects of this method (e.g., ITU-R Rec. BS.1387, ITU-R Rec. BS.1116 and ITU-R Rec. BS.562-3). For details of this complex issue see the definitive overview paper by Thiede, et al., "PEAQ -- The ITU Standard for Objective Measurement of Perceived Audio Quality," J. Audio Eng. Soc., vol. 48 [Audio Engineering Society, January/February 2000]. See also CRC's (Communication Research Centre) excellent summary with the same title.
Pearson, Donald ("Dr. Don") Michael (1942-2006) American live sound engineer who pioneered high-fidelity large-scale sound reinforcement systems. His systems powered many famous groups including Jefferson Airplane, Hot Tuna, Jefferson Starship, Grateful Dead, Andrea Bocelli and the Dave Matthews Band.
Pease, Bob (1940-2011) Famous American engineer known for his innovative analog IC designs, popular for his "Pease Porridge" column in Electronic Design magazine, and writing about hiking and biking in exotic places like Tibet.
PEC (parallel earth conductor) Modern best practices for EMC in installations (per IEC 61000-5-2:1998) require the use of trays, conduits and heavy-gauge earth conductors, known as "parallel earth conductors" (PEC) to divert power currents away from cables and their shields. See Williams' EMC for Systems and Installations for full details.
PEC (protective earth conductor) Conductor to be connected between the protective earth terminal and an external protective earthing system.
peer-to-peer abbreviated P2P A network term popularly used to mean an equal access network where every node can send/receive data at any time without waiting for permission, i.e., each node can act as a client or server. An example would be a group of computers that communicate directly with each other, rather than through a central server.
pennywhistle See: tin whistle.
pentode Electronics. A vacuum tube consisting of five elements: cathode, control grid, screen grid, suppressor grid and plate.
Percentage Articulation Loss of Consonants (%ALCONS) A term first published in the paper by V. M. A. Peutz. "Articulation Loss of Consonants as a Criteria for Speech Transmission in a Room," J. Audio Eng. Soc., Vol. 19, Dec 1971. It is a measure of room speech intelligibility based on the measured RT60 time and dimensions of the room, combined and expressed as a percent, where 0% (no loss of consonants) is perfect, 10% is poor, and 15% is intolerable. Popularized by Syn-Aud-Con's Pat Brown who teaches how to use it to direct loudspeaker line arrays. See Peter Mapp's excellent AES preprint 5668 presented at the 113th Convention of the Audio Engineering Society, Los Angeles, October 2002. Contrast with STI and RASTI.
perceptual coding A lossy digital audio data compression technique based on the human hearing mechanisms of masking and critical bands. AC-3 and AAC are examples of digital audio data compression schemes based on perceptual coding.
perfect pitch See: absolute pitch.
period Abbr. T, t 1. The period of a periodic function is the smallest time interval over which the function repeats itself. (For example, the period of a sine wave is the amount of time, T, it takes for the waveform to pass through 360 degrees. Also, it is the reciprocal of the frequency itself: i.e., T = 1/f.) 2. Mathematics. a. The least interval in the range of the independent variable of a periodic function of a real variable in which all possible values of the dependent variable are assumed. b. A group of digits separated by commas in a written number. c. The number of digits that repeat in a repeating decimal. For example, 1/7 = 0.142857142857... has a six-digit period. [AHD]
periodic motion Motion that repeats itself at regular or predictable intervals.
peripheral Equipment physically independent of, but which may interface to a computer or a controller.
permeability Magnetics. A general term used to express various relationships between magnetic induction and magnetizing force. [IEEE]
permittivity Abbr. ε A measure of the ability of a material to resist the formation of an electric field within it. Also called dielectric constant, relative permittivity. [AHD]
personal monitors Headphones. A special earpiece or earplug containing high quality miniature loudspeaker systems, similar to hearing aids, used for on-stage and recording studio purposes in lieu of traditional floor foldback monitors.
PET (protective earth terminal) Terminal connected to conductive parts of Class I equipment for safety purposes. This terminal is intended to be connected to an external earthing system by a PEC (protective earth conductor).
peta- Prefix for one quadrillion (1015), abbreviated P.
petabyte A unit of information or computer storage equal to one quadrillion bytes, or 1024 terabytes. It is commonly abbreviated PB, when used with byte multiples (however should be peti-), the prefix may indicate a power of either 10005 or 10245, so the exact number may be either: 1015or 250.
peti- Symbol Pi New term standardized by the IEC (IEC 60027-2) to represent binary multiples of 10245. It differentiates between decimal and binary multipliers. The abbreviation, PB, should not be used for binary numbers.
PFC (power-factor-corrected) See power-factor-corrected.
PFL (pre-fade listen) A term used on recording consoles and mixers, referring to a signal taken before the main channel fader. The significance is this signal is not affected by the fader position. Normally used to monitor (via headphones) to an individual input (or a small group of inputs) without affecting the main outputs, particularly useful in that it allows listening to an input with its fader all the way down (off). In broadcast this function is often called cueing, while recording or live-sound users may also refer to it as soloing. Compare with AFL and APL.
phantom power Invented by Georg Neumann in 1966, the term given to the standardized scheme of providing power supply voltage to certain microphones using the same two lines as the balanced audio path. The international standard is IEC 60268-15, derived from the original German standard DIN 45 596. It specifies three DC voltage levels of 48 volts, 24 volts and 12 volts, delivered through 6.8k ohms, 1.2k ohms, and 680 ohms matched resistors respectively, capable of delivering 10-15 mA. The design calls for both signal conductors to have the same DC potential. This allows the use of microphone connections either for microphones without built-in preamps, such as dynamic types, or for microphones with built-in preamps such as condenser and electret types.
Why 48 volts is an interesting question. The answer is three-fold: 1) 48 volts is an exact multiple of the 1.5 volt battery cell; 2) 48 volts has been the telephone communication standard since before 1900; and 3) both of these combine to give the background to the explanation direct from Jürgen Breitlow and Stephen Peus at Neumann:
"In 1966, a Neumann engineer presented the latest developments in the field of studio microphones at Norwegian Radio and Television in Oslo. The first transistorized condenser microphones were shown at that time, together with the well-known tube microphones.
For compatibility reasons, Norwegian Radio wanted the transistor microphones to be supplied with a phantom powering system. Due to the limited amount of daylight available there in winter, an auxiliary lighting system was installed in the studios — fed from a central 48 V supply. This voltage would also be used for phantom powering the microphones.
So the 48 volt phantom powering system, which was later standardized in DIN 45 596, came into existence."
Phantom Power Mini-tutorial: Much confusion surrounds phantom power. This is an area where you need to make informed decisions: Is it provided? Do you need it? Is it the correct voltage, and does it source enough current for your microphone? There is a huge myth circulating that microphones sound better running from 48 volts, as opposed to, say, 12 volts, or that you can increase the dynamic range of a microphone by using higher phantom power. For the overwhelming majority of microphones both of these beliefs are false. Most condenser microphones require phantom power in the range of 12-48 VDC, with many extending the range to 9-52 VDC, leaving only a very few that actually require just 48 VDC. The reason is that internally most designs use some form of current source to drive a low voltage zener (usually 5 volts; sometimes higher) which determines the polarization voltage and powers the electronics. The significance is that neither runs off the raw phantom power, they both are powered from a fixed and regulated low voltage source inside the mic. Increasing the phantom power voltage is never seen by the microphone element or electronics, it only increases the voltage across the current source. But there are exceptions, so check the manufacturer, and don't make assumptions based on hearsay. From the RaneNote Selecting Mic Preamps.
phase Audio signals are complex AC (alternating current) periodic phenomena expressed mathematically as phasors, or vectors. Phase refers to a particular value of t (time) for any periodic function, i.e. it is the relationship between a reference point and the fractional part of the period through which the signal has advanced relative to an arbitrary origin. [The origin is usually taken at the last previous passage through zero from the negative to the positive direction -- IEEE.] See Georgia State University's great website HyperPhysics for more detail.
phase cancellation When two signals have the same exact time relationship to each other, they are said to be "in-phase;" if they do not, they are said to be "out-of-phase." (Compare with polarity) If two out-of-phase signals add together, since this is vector arithmetic (see phasor), they will, in fact, subtract from one another. This is called phase cancellation. Another type of phase cancellation occurs when water waves interact. One wave's energy becomes stronger when two waves collide in-phase (summing) and becomes weaker when they collide out-of-phase (cancelling).
phase delay A phase-shifted sine wave appears displaced in time from the input waveform. This displacement is called phase delay and is usually constant for all frequencies of interest. Used as another name for group delay; however there are instances where they are not the same, for example systems exhibiting ripple in their phase vs. frequency characteristics.
phase lag and phase lead Phase shift caused by reactive elements (capacitors and inductors) that either subtracts (lag) or adds (lead) degrees of shift. See the RaneNote Linkwitz-Riley Crossovers: A Primer.
phase linear 1. Chiefly a European phrase meaning "linear phase." Any system which accurately preserves phase relationships between frequencies, i.e., that exhibits pure delay. See group delay. 2. Consumer hi-fi company where the Rane owners worked before starting Rane Corporation.
phase lock loop Abbr. PLL A circuit for synchronizing a variable local oscillator with the phase of a transmitted signal. The circuit acts as a phase detector by comparing the frequency of a known oscillator with an incoming signal and then feeds back the output of the detector to keep the oscillator in phase with the incoming frequency. Commonly used for bit-synchronization.
phase plug Loudspeakers. A device and technique that extends high frequency response by preventing cancellation of high frequency waves. Many designs exist. See Cliff Henricksen's AES paper: "Phase Plug Modelling and Analysis: Circumferential Versus Radial Types"
phaser Also called a "phase shifter," this is an electronic device creating an effect similar to flanging, but not as pronounced. Based on phase shift (frequency dependent), rather than true signal delay (frequency independent), the phaser is much easier and cheaper to construct. Using a relatively simple narrow notch filter (all-pass filters also were used) and sweeping it up and down through some frequency range, then summing this output with the original input, creates the desired effect. Narrow notch filters are characterized by having sudden and extreme phase shifts just before and just after the deep notch. This generates the needed phase shifts for the ever-changing magnitude cancellations.
phase shift The fraction of a complete cycle elapsed as measured from a specified reference point and expressed as an angle. See the RaneNote Exposing Equalizer Mythology. Also see discussion of phase shift vs. inversion at polarity.
phasor 1. A complex number expressing the magnitude and phase of a time-varying quantity. It is math shorthand for complex numbers. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems. [Example: 1.5 /27° is a phasor representing a vector with a magnitude of 1.5 and a phase angle of 27 degrees.] 2. For some unknown reason, used a lot by Star Fleet personnel.
phat, phatter, phattest Slang Excellent; first-rate: phat fashion; a phat rapper. [Earlier, sexy (said of a woman), of unknown origin.] [AHD]
See Livio for all the fascinating details of this most intriguing number.
Phoenix-blocks (or -connectors or -strips) A term, becoming generic, meaning disconnectable, or plugable terminal blocks, after Phoenix Contact connector company, although dozens of companies make them. Also called Euroblocks. See connectors.
phone jack Same as 1/4" TRS, see connectors.
phoneme The smallest phonetic unit in a language that is capable of conveying a distinction in meaning, as the m of mat and the b of bat in English. [AHD] Phonemes consist of the vowels and consonants that make up English words.
phonetics The branch of linguistics that deals with the sounds of speech and their production, combination, description, and representation by written symbols. [AHD]
phonograph 1. Literally means "writing sound", a term coined from Greek roots. 2. A machine that reproduces sound by means of a stylus in contact with a grooved rotating disk. [AHD] 3. "An irritating toy that restores life to dead noises." -- Ambrose Bierce.
phonograph cartridge See pickup.
phonography Music. Literally "sound-writing," this term refers to field audio recordings used in music compositions. Speech. 1. The science or practice of transcribing speech by means of symbols representing elements of sound; phonetic transcription. 2. A system of shorthand based on phonetic transcription. [AHD]
phono jack Same as RCA, see connectors.
phonology 1. The study of speech sounds in language or a language with reference to their distribution and patterning and to tacit rules governing pronunciation. 2. The sound system of a language: the phonology of English. [AHD]
phonon The quantum of acoustic or vibrational energy, considered a discrete particle and used especially in mathematical models to calculate thermal and vibrational properties of solids. [AHD]
phonon laser A nanoscale laser-like device that uses sound waves instead of light, i.e., it uses phonons, so it could rightly use the acronym "phaser" for phonon amplification by stimulated emission of radiation--not to be confused with the other phaser.
physics Some claim that studying physics is all you need for a complete education -- after a visit to HyperPhysics you may agree.
pi Symbol π (Greek lower-case pi) 1. Mathematics. A transcendental number, approximately 3.14159, represented by the Greek lower-case pi symbol, that expresses the ratio of the circumference to the diameter of a circle and appears as a constant in many mathematical expressions. [AHD] 2. Filters. Equal to 180 degrees or integral multiples thereof. (Why chose pi as the letter to represent the number 3.141592...? Because the letter pi in Greek is like our letter p, as in perimeter (or circumference).) See: Beckmann for in-depth history. For the most enjoyable anti-pi rant see Vi Hart.
PI 14 See Pseudoacoustic Infector.
piano A musical instrument with a manual keyboard actuating hammers that strike wire strings, producing sounds that may be softened or sustained by means of pedals. [AHD] Italian Bartolomeo Cristofori invented the first hammer-operated piano in 1700.
pianoforte Original Italian-derived name for the musical instrument now shortened to "piano."
piccolo Musical Instrument. A small flute pitched an octave above a regular flute. [AHD]
piccolo snare Muscial Instrument. A snare drum that is about half as deep as a regular snare.
Pickathon Held in Happy Valley, OR, one of the best 'small' (3,500) music festivals, very eco- and family-friendly.
picket fencing See multipath.
pickup Transducers. A device that "picks up" sound and converts it into an electrical signal. Many technologies exist, from the most popular electromagnetic models (magnetic pickups) found on electric guitars to piezoelectric models seen on acoustic instruments and used in early phonograph cartridges (soon replaced with electromagnetic models using either moving magnet or moving coil technologies). Music.See upbeat.
pickup patterns See: microphone polar patterns.
PICO (Program In, Chip Out) Hewlett-Packard technology that use computers to design computers.
picofarad Abbr. pF One trillionth (10-12) of a farad.
picowatt Abbr. pW One trillionth (10-12) of a watt.
piezo Transducers. Greek, to press tight, squeeze. Shortened form for piezoelectric, the name given to a class of materials (dielectric crystals) that produce electricity or become polarized when mechanically strained or stressed. In pro audio used to create pickups, microphones and loudspeakers or buzzers, and in digital circuits quartz crystals for stable timing references.
PIGNOSE® The registered trademark of the industry's first truly portable guitar amplifier, which debuted at the Chicago Summer NAMM show in 1973. The origin of the name remains a mystery, although the product was patented by Wayne Kimbell and Richard Edlund (U.S. Patent 3,860,755 Novel Portable Amplifier and Speaker ),but the name, Pignose, was not mentioned.
pin-1 problem Phrase created by Neil A. Muncy (Canadian electroacoustic system consultant; also see PSW Live Chat With Neil Muncy) to describe the improper connection of the "pin-1" terminal of XLR connectors found on analog pro audio equipment. The correct way to terminate pin-1 of XLR connectors is to bond it to the chassis immediately at the entry and exit points. It should not be connected to circuit signal ground. Equipment with pin-1 left open, or connected to circuit signal ground is said to suffer from a "pin-1 problem." See AES48, Steve Macatee's Considerations in Grounding and Shielding, the RaneNote Sound System Interconnection, Philip Giddings' "A New and Important Audio Equipment Evaluation Criteria," and Tony Waldron and Keith Armstrong, "Bonding Cable Shields at Both Ends to Reduce Noise," EMC Compliance Journal, May 2002.
pinging Networks. A technique for determining whether a specific IP address is accessible. It works by sending a packet to the specified address and waiting for a reply (much like sonar does, hence the name).
pin jack Same as RCA, see connectors.
Pink Floyd British rock group founded in 1965 by Roger Keith ("Syd") Barrett (1946-2006), Nick Mason, Roger Waters and Richard Wright. The name came from two American bluesmen, Pink Anderson and Floyd Council.
pink noise Pink noise is a random noise source characterized by a flat amplitude response per octave band of frequency (or any constant percentage bandwidth), i.e., it has equal energy, or constant power, per octave. Passing white noise through a filter having a 3 dB/octave roll-off rate creates pink noise. See white noise discussion for details. Due to this roll-off, pink noise sounds less bright and richer in low frequencies than white noise. Since pink noise has the same energy in each 1/3-octave band, it is the preferred sound source for many acoustical measurements due to the critical band concept of human hearing. The name comes from the filtering of white noise. White noise is analogous to white light in that it contains all audible frequencies distributed uniformly throughout the spectrum. Passing white light through a prism (a form of filter) breaks it down into a range of colors. Examination shows that red light is characterized by the longer wavelengths of light, i.e., light in the lower frequency region. Similarly, pink noise has higher energy in the low frequencies, hence the somewhat tongue-in-cheek term pink. See noise color.
Pinkpop The Netherlands' oldest music festival, held in Landgraaf in the south of Holland. The name is a play of words coming from the Dutch word for Pentecost, "Pinksteren," since the festival is usually held over the Pentecost weekend.
pipa Musical Instrument. Chinese 4-string lute with 31 frets and a pear-shaped body.
pipe Saxophone. [Decharne]
pipe organ See: organ.
pistonphone Microphones. A calibration device consisting of a chamber and moving diaphragm (piston) that creates a precise pressure at a specific frequency. The frequency is typically 250 Hz with a standard pressure of 120-125 dB SPL. One popular model is the Brüel & Kjær Type 4228.
pitch Frequency or tone of a sound.
pitch ribbon See ribbon controller.
pitch-shifting or pitch-transposing Recording. An effect that changes the pitch (frequency or tone) of musical notes without changing their length, or timing. For example, fast-forwarding an audio cassette results in a higher pitched version of the music at an increased pace. Pitch-shifting does the same thing without changing the music speed. One way to accomplish this is to use continuous wavelet transform, where the musical signal is decomposed into separate wavelets and processed. First, the pitch is modified by a constant related to the required pitch change, then the time scale is adjusted appropriately.
pitter-patter A rapid series of light tapping sounds. To make or move with a series of light tapping sounds: rain pitter-pattering on the roof. [AHD]
placement equalization or placement EQ Term coined by Tomlinson Holman (of THX fame) to mean moving around the loudspeaker and listener until the room response (at the listener) is smoothest.
plainsong Music. 1. Gregorian chant. 2. Monophonic medieval liturgical music without strict meter and traditionally sung without accompaniment. In both senses also called plainchant. [AHD]
planar 1. Of, relating to, or situated in a plane. 2. Flat: a planar surface. 3. Having a two-dimensional characteristic. [AHD]
PLD (programmable logic device) The generic name for an integrated circuit offering a vast array of logic function building blocks that the circuit designer defines (programs) to interconnect for specific applications.
plectrum Musical Instruments. A small thin piece of metal, plastic, bone, or similar material, used to pluck the strings of certain instruments, such as the guitar or lute. [AHD] [Fancy name for a pick.]
plenum 1. A ductwork system in which air is at a pressure greater than that of the outside atmosphere. 2. Such a system located in the space above a suspended ceiling, used to circulate air back to a building's HVAC.
plenum cable The type of cable used when smoke retardant properties are required. Plenum cable is specifically designed for use in a plenum area (see above) which is typically used as the distribution system in buildings. Most cities requiring all cable ran through a plenum ceiling to be plenum cable which has insulated conductors jacketed with PVDF (polyvinylidene difloride) -- a material providing low flame spread and low smoke producing properties. Underwriters Laboratories approved plenum cables for non-conduit applications located in environmental air spaces. This low cost alternative has replaced traditional conduit use in many commercial installations.
PLL See phase lock loop.
plosive Linguistics. Of, relating to, or being a speech sound produced by complete closure of the oral passage and subsequent release accompanied by a burst of air, as in the sound (p) in pit or (d) in dog. A plosive speech sound. [From explosive.] [AHD]
plug See jacks and plugs.
plugging Motors. Act of reversing the motor connections to develop a strong counter torque to decelerate.
plugin or plug-in Software. An accessory program that extends the capabilities of an existing application. Also called add-in or add-on. [AHD] First developed in the mid '70s; back in the days of the Univac mainframe computer.
plumbing Trumpet. [Decharne]
PM See personal monitors.
PMPO (peak music power output or peak momentary performance output) An arbitrary made-up specification (marketing gimmick) that supposedly measures the total maximum power output from an amplifier at a given THD+N level during a brief transient. Also used to express dubious loudspeaker power ratings. Typically there is a 12-to-1 difference between PMPO and real apparent power (67:1 is the record).
PMPO (purely mythical power output) Tongue-in-cheek alternate satirical definition to the real one above. [Source unknown but thanks to IH in the UK for the tip!]
PnP (plug 'n play) 1. Computers. The technology that lets certain operation systems (Windows 95, others) automatically detect and configure most of the adapters and peripherals connected to or sitting inside a PC. 2. Any system with automatic detection and configuration of auxiliary devices.
polarity A signal's electromechanical potential with respect to a reference potential. For example, if a loudspeaker cone moves forward when a positive voltage is applied between its red and black terminals, then it is said to have a positive polarity. A microphone has positive polarity if a positive pressure on its diaphragm results in a positive output voltage. [Usage Note: polarity vs. phase shift: polarity refers to a signal's reference NOT to its phase shift. Being 180° out-of-phase and having inverse polarity are DIFFERENT things. We wrongly say something is out-of-phase when we mean it is inverted. One takes time; the other does not.]
polar response See: microphone polar response.
polyphonic Music. Two or more independent melodic parts sounded together. [AHD]
Pooh "I am a bear of very little brain, and long words bother me." A.A. Milne, Winnie-the-Pooh, Ch. 4. [Crystal]
popcorn noise Solid-state physics. Noise primarily found in integrated circuit audio amplifiers that exhibit a sizzling, frying hot-grease kind of sound, similar to popcorn popping. Found to be due to manufacturing defects in the form of metallic impurities in the junctions, often caused by dirty fabrication lines. The frequency spectrum typically conforms to 1/frequency-squared. See red/brown noise under noise color.
poppysmic Word for the sound made by smacking of the lips. Hit the link for more.
portamento Music. A smooth uninterrupted glide in passing from one tone to another, especially with the voice or a bowed stringed instrument. [AHD]
Portastudio® Recording. Registered trademark name for TEAC's Model 144, the world's first 4-track cassette recorder introduced at the 1979 New York AES show. Invented by Yoshiharu Abe, one of TEAC's founders.
Porter, Bill (1931-2010) American recording engineer who created hits with Chet Atkins, Roy Orbison, Everly Brothers and Elvis Presley to name only a few.
poseur One who affects a particular attribute, attitude, or identity to impress or influence others. [AHD] (There are a lot of poseurs in the pro audio business.)
post-echo See print-through.
pot (lowercase) Shorten form of potentiometer (and if you think I'm gonna make some cheap joke about the smokin' kind, you're crazy).
potential difference The amount of energy per unit charge needed to move a charged particle from a reference point to a designated point in a static electric field; voltage. Also called potential. [AHD]
potentiometer A three-terminal variable resistor. Two terminals connect to the ends of the resistor, while the third terminal is attached to a movable device that makes contact with the resistive element. The movable terminal, or slider, is capable of being positioned from one end of the element to the other. Many physical arrangements exist, with the rotary design being the most common, followed by linear motion (used in graphic equalizers, for example), all the way to tiny SMT devices. Often used as voltage dividers in electronic circuits, the input voltage is applied to the top of the resistive element, while the other end is tied to ground or a common reference and the output is taken from the slider. When the slider is positioned to the top extreme, the output equals the input, or the entire voltage; moving it to the bottom extreme gives an output of zero volts; and every possible level between is available as the slider is moved from one end to the other. The most common application uses this arrangement to control the volume of an audio device. In this manner the voltage, or electrical potential is varied, hence, a potentiometer. The taper of the pot controls the rate at which the voltage changes as the slider is moved. The taper defines the amount of resistive change as a function of travel. Several popular examples follow:
POTS (uppercase) Acronym for plain old telephone system. The normal single line basic land telephone service. Often used in reference to modems associated with regular telephone land lines. See the RaneNote Interfacing Audio and POTS. Compare with PANS.
power 1. Electricity a. The product of applied voltage (potential difference) and current in a direct-current circuit (or the voltage squared divided by the resistance, or the current squared times the resistance). b. The product of the effective values of the voltage and current with the cosine of the phase angle (between current and voltage) in an alternating-current circuit. See apparent power and rms power 2. Physics The rate at which work is done, expressed as the amount of work per unit time, and measured in units such as the watt (1 joule per second, which equals the power dissipated (as heat) by 1 ohm of resistance when 1 ampere of current passes through it) and horsepower (equal to 745.7 watts). [AHD]
power amplifier See amplifier.
power amplifier dummy load See amplifier dummy load.
power amplifier sensitivity See sensitivity.
power compression Loudspeakers. The phenomena where the power transfer from the amplifier to the loudspeaker decreases as the loudspeaker voice coil heats up. As the voice coil heats its resistance increases reducing the resulting power for the same applied voltage. Typical compression numbers run from 3 dB to 6 dB. QSC shows a nice curve of power compression in their tech note on Power Limiting.
power equations See: Joule's Law.
power factor Abbr. PF Electronics. The ratio of the total (or real) power in watts (resistive load; aka real power) to the total apparent power in voltamperes (VA) (reactive load). The difference between watts and VA is due to reactive load impedance. Apparent power equals watts only for a purely resistive load (i.e., zero degrees phase shift between the applied voltage and the resultant current). Power factor is best thought of intuitively as the multiplier (ranging between 0 and 1) that you must use to obtain the real power from the apparent power. For example if you measure the rms voltage and current of a circuit and multiply them together you obtain the apparent power, but you must multiply this value by the power factor to obtain the real power. If the load is purely resistive then the phase difference between the voltage and current will be zero and the power factor will be one, and the apparent power will equal the true power -- but only for a resistive load. For a reactive load (any load with inductive and/or capacitive reactance, i.e., any real load) there will be a phase difference between the voltage and the current due to the phase delay introduced by the reactive elements. Simply put, since the maximum voltage and current do not occur at the same instant of time the amount of power developed is less than the measured rms voltage and current multiplied together. Since power factor is a ratio, and hence unitless, it can be expressed in several ways -- all of them equal. It is the ratio of watts to voltamperes, of resistance to reactance, and if the phase shift in degrees is known (phase angle), it is the cosine of that angle, or cos ?. If the angle is zero then PF = 1, and if the angle is 90° then PF = 0.
power-factor-corrected (PFC) 1. General. Power factor correction reduces phase error and improves wave shape in electrical sources and power supplies. The PFC circuitry acts to make the load appear more resistive. Power factor varies between zero and one in value. It is unity, or one, when it is purely restive. This is when the input current wave shape and phase exactly match the input voltage wave shape and phase. AC mains voltage is supposed to be sinusoidal, so a power factor of unity requires in-phase, sinusoidal current. Power factor correction is any passive or active measure taken to improve the phase relationship and/or harmonic content (shape) of current so that it matches the input voltage. 2. Passive. Any system that has a passive power-factor-correcting device, such as an inductor or capacitor, installed to reduce the phase difference between the rms voltage and rms current. For example, adding series inductance to reduce the phase lead between voltage and current seen with standard rectifier/capacitor power supplies. 3. Active. Any system using active circuit elements such as switching transistors, in conjunction with reactive components, to improve power factor. The switching elements operate at relatively high frequencies, allowing smaller reactive components (than required by passive methods) to produce the desired results. The majority of active PFC circuits work to insure that mains currents will flow, even when instantaneous line voltage is low. Very high power factor values are obtained by actively controlling instantaneous line current so that it remains proportional to the average power demanded by the load.
[PFC Mini-tutorial: Real power, i.e., purely resistive load, is measured in watts and gets converted to audio power (to drive loudspeakers, for instance). Apparent power is measured in volt-amperes and is what blows circuit breakers. This is because circuit breakers only measure current. As power factor gets worse circuit breaker ratings must go up to prevent tripped breakers. A power-factor-corrected system allows full power out of each branch circuit. Electronic equipment without PFC draws a surprising amount of apparent power because of the poor power factor.
Due to the impedance of the AC mains wiring, the high peak currents associated with poor power factor affect the wave shape of the mains voltage. This is a kind of harmonic distortion that can adversely affect some types of equipment. For example, it's well known that the ubiquitous 60 Hz and 120 Hz magnetic fields can couple to 'ground loops' and cause annoying hum. However the presence of significant mains waveform distortion can make this sort of thing a problem at higher line harmonics (e.g., 180 Hz, 240 Hz, etc.) where magnetic coupling is progressively more effective (proportional to frequency) and the hum is increasingly annoying. Thanks, PM!]
Power over Ethernet See PoE.
PowerPC A super powerful RISC processor PC jointly developed by IBM, Apple and Motorola, designed to run any PC operating system (MS-DOS, UNIX, Windows, OS/2, Mac OS. etc.). Featured in Apple's line of "PowerMac" computers.
power spectral density See PSD.
power supply rejection ratio See PSRR.
ppm (lowercase) ( parts per million) Indicates one part in 106, with a value of 1 × 10-6.
PPM (uppercase) (peak program meter) An audio meter originally developed in Europe to accurately measure and display peak audio signals (as opposed to average audio signals; see VU meter). The PPM augments the VU meter and it is normal to find both in modern recording studios. The PPM is particularly valuable for digital audio recording or signal processing due to the critical monitoring required to prevent exceeding 0 dBFS and reducing overs. There are two standards: IEC 60268-10 for analog meters and IEC 60268-18 for digital meters. [These are available to buy on the IEC website.] An interesting aspect of PPM design is that rather than respond instantaneously to peaks, they require a finite 5 ms integration time, so that only peaks wide enough to be audible are displayed. IEC 60268-10 translates this into a response that is 1 dB down from steady-state for a 10 ms tone burst, 2 dB down for a 5 ms burst, and 4 dB down for a 3 ms tone burst -- requirements satisfied by an attack time constant of 1.7 ms. The IEC specified decay rate of 1.5 seconds to a -20 dB level can be met with a 650 ms time constant.
Pramanik stylus Phonographs. A ultra-lightweight 4-channel phono cartridge with a Beryllium cantilever and a multifaceted stylus invented by Subir "Pram" Pramanik of Bang & Olufsen in 1973.
Prandtl number See Grashof.
preamplifier See amplifier.
pre-preamplifier See head amp.
precedence effect See Haas Effect.
pre-echo See print-through.
pre-mastering See mastering.
pressure gradient microphone Microphone. If both the front and rear of a diaphragm are exposed to a sound field, then the force that vibrates the diaphragm results from the difference between the sound pressures in front and to the rear of the diaphragm (called the pressure gradient). The magnitude of the driving force depends on the distance between the front and rear sound entries, the frequency, and the angle of incidence and is therefore a directional variable which can be utilized to design directional microphones. Cardioid, figure 8, or hypercardioid polar patterns can be achieved by incorporating appropriate sound paths. [From AKG Acoustics Glossary] Also see ribbon microphone.
pressure zone microphone See PZM.
pretzel A French horn. [Decharne]
Primavera Sound Music festival held yearly May-June since 2001 in Barcelona, Spain, featuring "... an artistic line marked by pop, rock and the most underground tendencies of dance music." [From website]
principal component analysis See: PCA.
print-through The name for the magnetic tape recording phenomena where the act of layering, or winding layer upon layer of tape causes the flux from one layer to magnetize the adjacent layer, thus printing through from one layer onto another layer. Also called crosstalk or interlayer transfer. The most vulnerable parts of the magnetic tape are the blank spots, particularly leaders and spaces between material that happen to occur adjacent to loud passages. Two other terms come from print-through: on layers played back before loud passages it gives a pre-echo, whereas on playback following the loud passage it gives a post-echo.
printed circuit board See: PCB.
Pritts, Roy (1937-2007) American musician and recording engineer who founded the Music Technology/Recording Arts program at the University of Colorado in 1971.
probability density function, or pdf, or p.d.f. The name given to a mathematical function that defines a continuous interval (i.e., one without gaps), or curve, such that the area under the curve (and above the x-axis, i.e., the probability is always positive) described by the function is unity, or equals one, or 100% -- whatever way you want to look at it. It simply means that all possibilities are represented. The most familiar example is the famous "bell-shaped curve" or just "bell curve." The bell curve is a symmetrical curve representing a normal or Gaussian distribution. Also called a normal curve. When applied to school grading, for example, it says that there is the highest probability that a student picked at random will receive a C-grade, and rapidly decreasing probabilities that any one student will receive a B- or A-grade, going in one direction, or a D- or F-grade, going in the other direction. Technically, it means the probability of a random variable taking values between two real numbers, or extremes (an A or an F) is given by the area under the curve between these two points.
proceleration "The acceleration of acceleration." [A Dictionary of the Near Future by Douglas Coupland, NY Times, September 12, 2010.] [Which is actually called jerk.]
production glossary Live Sound. A handy guide to a unique vocabulary of the live sound production industry by Craig Leerman.
production master Recording. See mastering.
Programming, Law of The law states that every program contains at least one bug. The law further states that every program can be shortened by at least one instruction. Therefore, the law concludes, every program can be reduced to one instruction that does not work. The law is not wrong. [Thanks TP.]
progressive array See line arrays.
proof "Evidence having a shade more of plausibility than of unlikelihood. The testimony of two credible witnesses as opposed to that of only one." -- Ambrose Bierce.
propagation The motion of waves through or along a medium. For electromagnetic waves, propagation may occur in a vacuum as well as in material media.
propagation delay The initial delay through a signal processing box, i.e., the time it takes for a signal to pass once through a device. It is the unavoidable and uncontrollable (by the user) delay inherent to the processing electronics. Propagation delay is caused most often in analog electronics by phase delay in filter networks, and in digital electronics by computational delay in microprocessors and DSP devices, as well as data conversion. In networking, the time it takes for a signal to pass through a channel. Similar to latency but normally restricted to signal processing devices, rather than computer operations.
Prophet-5 Musical Instrument. The first programmable polyphonic synthesizer developed by Sequential Circuits in 1978. The "5" referred to its being able to play five notes simultaneously.
proportional-Q graphic equalizer (also variable-Q) Term applied to graphic and rotary equalizers describing bandwidth behavior as a function of boost/cut levels. The term "proportional-Q" is preferred as being more accurate and less ambiguous than "variable-Q." If nothing else, "variable-Q" suggests the unit allows the user to vary (set) the Q, when no such controls exist. The bandwidth varies inversely proportional to boost (or cut) amounts, being very wide for small boost/cut levels and becoming very narrow for large boost/cut levels. The skirts, however, remain constant for all boost/cut levels. See the RaneNote Operator Adjustable Equalizers. Compare with constant-Q and true response graphic equalizers.
prosumer Shortened form of professional + consumer, often used to refer to home recording studio equipment.
protocol A specific set of rules, procedures or conventions relating to format and timing of data transmission between two devices. A standard procedure that two data devices must accept and use to be able to understand each other.
proximity effect Microphones. Term for the increase in low frequency response (bass boost), or sensitivity, of most directional microphones when the sound source is within a few inches. Click the link for all the details.
PSD (power spectral density) Physics. A measure of how the power in a signal changes over frequency. It is the total power in a specified bandwidth divided by the specified bandwidth expressed in watts per hertz or dBm per hertz.
Pseudoacoustic Infector Term coined by Rane Corporation for their mythical product, the PI 14, first introduced in 1988, which almost caught the attention of the music industry. An acoustic stimulator designed to add a little bit of This and a little bit of That to recordings, to give them a sense of Now previously unobtainable. Rane's PI 14 introduced a unique Here-to-There (and-Back-Again) pan control. Transformer operation required the Jensen JE-EP-ERs when coupling directly into a Crown Belchfire BF-6000SUX for playback through an Electro-Voice Rearaxial Softspeaker. Today, PI 14s are considered quite scarce and highly collectable.
pseudo-balanced output A two-wire (with overall shield) interfacing technique for an unbalanced output where a resistor equal to the output resistor is placed in series with the return leg (either pin-3 for an XLR connector or the ring lead for an 1/4" TRS connector). This makes both lines measure the same impedance when looking back from the receiver and allows the common-mode rejection feature of the input differential amplifier to function. See the RaneNote Sound System Interconnection.
psi-network Quadraphonics. A special two-port all-pass network that creates a 90 degree phase shift between the two output signals over the full audio bandwidth. Used in encoding and decoding a 4-channel effect into and back from a 2-channel medium. See for example U.S. Patent 3,761,628 Stereo-Quadraphonic Matrix System with Matrix or Discrete Sound Reproduction Capability granted to Ben Bauer and assigned to CBS in 1973. Also another Bauer U.S. Patent 3,940,559 Compatible four channel recording and reproducing system. For the DIY-er and/or mathematically curious see: McNulty Analog Wide Band Audio Phase Shift Networks.
PSK (phase-shift keying) The form of phase modulation in which the modulating function shifts the instantaneous phase of the modulated wave among predetermined discrete values. [IEEE]
PSPICE See SPICE.
psophometric See weighting filters
PSRR (power supply rejection ratio) Electronics. In the most general sense, a measure of a circuit's immunity to power supply noise and variations. For details see Nicholas Gray's Application Brief Power Supply Effects on Noise Performance.
psst Only word in the dictionary without a vowel. "Used to capture someone's attention inconspicuously." [AHD]
psychoacoustics The scientific study of the perception of sound. Called "the music of science" by Roederer.
PTT (push-to-talk) A pushbutton switch commonly found on paging and conference room microphones that must be engaged before speaking. Also prevalent in communication systems.
p-type semiconductor An extrinsic semiconductor in which the mobile hole concentration exceeds the conduction electron concentration. [IEEE]
public address See P.A.
PUFF CAD Electronics. Popular microwave circuit simulation program for laying out and analyzing microstrip and stripline circuits on IBM-compatible personal computers.
Pukkelpop Festival Annual three-day alternative music festival held mid summer in Hasselt, Belgium. Begun in 1985, it has grown each year and is now considered one of Europe's best music events.
pumping Dynamics Processors. Loud level variations caused by quick noticeable variations of level associated by use of heavy compression or limiting. [Izhaki]
punch-in/punch-out Recording studio: To engage/disengage record mode on a track previously recorded, usually for purposes of correcting unwanted segments.
punter Chiefly British Slang. A word with many meanings but the one found in pro audio usage refers to "... a member of an audience, a spectator, a paying quest; a participant in any activity." [OED]
Pupin, Michael I. (Anglicized name of Mihajlo Idvorski Pupin) (1858-1935) Serbian-American physicist who invented the Pupin coil (a special inductor) that greatly extended the range of long-distance telephone communication by adding inductance. These coils were placed at predetermined intervals along the transmitting wire (a process known as pupinization).
Puritanism "The haunting fear that someone, somewhere, may be happy." H. L. Mencken, A Book of Burlesques ( 1916).
PURLnet See ZigBee.
purple One of the few words in the English language without a rhyme -- some others are "month," "orange" & "silver."
purple noise See noise color.
PVC cable (polyvinyl chloride) The most common type of cable used when smoke retardant properties are not required, i.e., when a building's HVAC system is run through metal ducts - not open ceilings. This cable is sheathed in PVC, the standard jacketing of most electrical cable. PVC is a tough water and flame retardant material, but is not smoke retardant. If PVC catches fire, it emits noxious gases, and if the cable is run in a plenum area, the deadly gases can be dispersed throughout the building.
PVDF (polyvinylidene fluoride) Loudspeakers. A type of plastic exhibiting piezo-electric properties, used by Dr. Koh Seok-keun, P&I (Plasma & Ionbeam) Corporation, to produce a thin-membrane midrange/tweeter driver. The result is claimed to produce a near perfect vertical or horizontal radiation pattern.
PWM (pulse width modulation) A conversion method in which the widths of pulses in a pulse train represent the analog information. See the RaneNote Digital Dharma of Audio A/D Converters.
Pythagorean temperament The mathematical principles of musical harmony according to the Greek philosopher Pythagoras.
pyrophone Muscial Instrument. Click the link; this is too weird an instrument to describe in a few words.
PZM (pressure zone microphone) Patented by Ed Long & Ron Wickersham in 1982 (US 4,361,736), a technique and design where the microphone is mounted on a flat plate which acts as a reflective surface directing sound into the mic capsule. The PZM principle uses the compression and decompression of air between the plate and the membrane in parallel with the plate (the gap is very narrow, typically only a millimeter or less). This arrangement gives about 6 dB extra amplification of the signal, which means 6 dB less inherent electronic noise. Now owned by Crown International, a Harman International Company. For an incredible historical resource, see Crown's Mic Memo, a 503 page print version of their reference CD.