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Dictionary of Audio Terminology - W

W - Abbreviation for watt.

W3 - An abbreviation for World Wide Web.

Wachner, Brian Gary - (b.1945-1997) American engineer and founder of BGW Systems.

wah-wah pedal - (also wa-wa pedal) An electric guitar effects foot pedal that alters the sound in a wavering manner sounding somewhat like the human voice saying the word "wah." Made famous by Jimi Hendrix (and others) in the 1960s using an original Cry Baby pedal. In brass instruments, mostly trumpets, a similar sound is created by covering and uncovering the bell with a rubber toilet plunger.

Walker, Peter J. - (1916-2003) British engineer and inventor known as the founder of the legendary British audio company Quad.

walla - The film industry term for background crowd noises in a movie.

Wall of Sound - One of the most famous PA systems of all time, developed and used by the Grateful Dead in the early '70s.

Wally - Award given at LDI (Live Design International) trade show each year since its inception in 1992, named after Wally Russell. The full name is the Wally Russell Lifetime Achievement Award.

Walkman® - Registered trademark of the Sony Corporation originally for their portable audio cassette player. While Philips Norelco's Carry-Coder was first, Sony's Walkman's size and sound quality changed everything in 1979.

Walsh driver - Loudspeakers. A novel omnidirectional loudspeaker invented by Lincoln Walsh and granted U.S. Patent 3,424,873 in 1969 (filled in 1964). Called a coherent-sound loudspeaker, a Walsh driver is an inverted-cone that radiates sound all around "... by means of a conical diaphragm operating as a wave transmission line." It is claimed to "... obtain full frequency range, high quality sound omnidirectionally from a single radiator." [US Patent 3,424,873]. Walsh's invention led to the founding of Ohm Acoustics, the exclusive manufacturer of loudspeakers based on Walsh drivers, and whose President/Chief Engineer, John Strohbeen further developed Walsh's concepts (U.S. Patent 4,483,015, et. al.) into what they are today. Walsh, Lincoln (1903-1971) American engineer who developed the Walsh Driver and much more.

WAM - (Women's Audio Mission) San Francisco-based, non-profit organization dedicated to the advancement of women in music production and the recording arts.

WAN (wide area network) A computer and voice network bigger than a city or metropolitan area.

warp marker - A method that attaches a position in a music sample to a particular time in the song. It forces the software to arrive at a specific point in the music sample at a specific time.

waterfall display - (aka cumulative spectral decay) Loudspeakers. A two-dimensional, three-coordinate graph displaying frequency on the horizontal, amplitude on the vertical and time on the third leg, back-to-front. Used to display information about a loudspeaker's impulse response. This plot technique is first described and named by M. Bernam and L. Fincham in their paper, "The Application of Digital Techniques to the Measurement of Loudspeakers," Jour. AES Soc., vol. 25, no. 6, 1977, pp. 370-384, where they apply modern DSP techniques to make practical the original work done by D. E. L. Shorter in 1946 ("Loudspeaker Transient Response -- Its Measurement and Graphical Representation," B.B.C. Quart., vol. 1, p. 121 (1946).

Watermarking - Audio or video Embedded data code within the digitized audio or video image that can be recovered but which will not affect the quality of the product. Various methods exist, but all consist of very short (2-5 microseconds long) pieces of code containing all the relevant data about the copyright owner and performance royalties. All make use of the science of steganography.

watt - Abbr. W Electricity An International System unit of power equal to one joule per second. (After James Watt)

.WAV - File extension for a Wave file, the Microsoft format that is the de facto audio file format for PCs.

wave field synthesis - Abbr. WFS "A means by which a soundfield can be reconstructed within a listening area using an array of loudspeakers, enabling faithful spatial reproduction." From "Wavefield Synthesis," J. Audio Eng. Soc., Vol. 52, No. 5, May 2004, pp. 538-543. See also AES Monograph: Wave Field Synthesis by Diemer de Vries.

wavelength Symbol λ (Greek lower-case lambda) The distance between one peak or crest of a sine wave and the next corresponding peak or crest. The wavelength of any frequency may be found by dividing the speed of sound by the frequency.

wavelet - An algorithm used to efficiently compress and decompress the phase and frequency information contained in a transmitted signal.

wax a disc - To make a recording.

Weber, Dr. Walter - (1907-1940) German engineer best know for his application of AC tape bias to ferrite-oxide tape.

Weber, Wilhelm Eduard - (b1804-1891), German physicist famous for his study of the electrical structure of matter. The International System unit of magnetic flux is named after him.

Webcast - The real time (continuous stream) delivery of audio and video from a server to a client.

weber - Abbr. Wb The International System unit of magnetic flux, equal to the flux that produces in a circuit of one turn an electromotive force of one volt, when the flux is uniformly reduced to zero within one second. After Wilhelm Eduard Weber.

Web ring - A group of websites all sharing a common theme. For example, web rings exist for fans of certain bands, movies, TV shows, authors, racecar drivers, etc. Soon we will have a web ring for web rings.

Webster, Arthur G. - (b1863-1923) American scientist who developed the concept of acoustic impedance in 1919 and also contributed to the theory of horn loudspeakers.

wedge loudspeaker also monitor loudspeaker - The nickname for a loudspeaker used on stage to aid the musician in hearing the whole band; often shaped like a cheese or pie wedge.

WEEE - (Waste from Electrical and Electronic Equipment) European directive on disposal of electrical and electronic equipment. See RoHS.

weighted average - An average that takes into account the proportional relevance of each component, rather than treating each component equally. [IEEE Std 1680]

weighting filters - Special filters used in measuring loudness levels, and consequently carried over into audio noise measurements of equipment. The filter design "weights" or gives more attention to certain frequency bands than others. The goal is to obtain measurements that correlate well with the subjective perception of noise. (Technically termed psophometric [pronounced "so-fo-metric"] filters, after the psophometer, a device used to measure noise in telephone circuits, broadcast, and other audio communication equipment. A psophometer was a voltmeter with a set of weighting filters.) Weighting filters are a special type of band-limiting filters designed to compliment the way we hear. Since the ear's loudness vs. frequency response is not flat, it is argued, we should not try to correlate flat frequency vs. loudness measurements with what we hear. Fair enough. Five weighting filter designs dominate. See Below:

• A-weighting (not official but commonly written as dBA) The A-curve is a wide bandpass filter centered at 2.5 kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB attenuation at 20 kHz, therefore it tends to heavily roll-off the low end, with a more modest effect on high frequencies. It is the inverse of the 30-phon (or 30 dB-SPL) equal-loudness curve of Fletcher-Munson.

Editorial Note: Low-cost audio equipment often list an A-weighted noise spec -- not because it correlates well with our hearing -- but because it helps "hide" nasty low-frequency hum components that make for bad noise specs. Sometimes A-weighting can "improve" a noise spec by 10 dB. Words to the wise: always wonder what a manufacturer is hiding when they use A-weighting. "However, an exception has arisen: Digital products using A/D and D/A converters regularly spec S/N and dynamic range using A-weighting. This follows the semiconductor industry's practice of spec'ing delta-sigma data converters A-weighted. They do this because they use clever noise shaping tricks to create 24-bit converters with acceptable noise behavior. All these tricks squeeze the noise out of the audio bandwidth and push it up into the higher inaudible frequencies. The noise may be inaudible, but it is still measurable and can give misleading results unless limited. When used this way, the A-weighting filter rolls off the high frequency noise better than the flat 22 kHz filter and compares better with the listening experience. The fact that the low-end also rolls off is irrelevant in this application."

• C-weighting (not official but commonly written as dBC) The C-curve is "flat," but with limited bandwidth, with -3 dB corners of 31.5 Hz and 8 kHz, respectively.

• ITU-R 468-weighting (was CCIR, but since the CCIR became the ITU-R, the correct terminology today is ITU-R) This filter was designed to maximize its response to the types of impulsive noise often coupled into audio cables as they pass through telephone switching facilities. Additionally it turned out to correlate particularly well with noise perception, since modern research has shown that frequencies between 1 kHz and 9 kHz are more "annoying" than indicated by A-weighting curve testing. The ITU-R 468-curve peaks at 6.3 kHz, where it has 12 dB of gain (relative to 1 kHz). From here, it gently rolls off low frequencies at a 6 dB/octave rate, but it quickly attenuates high frequencies at ~30 dB/octave (it is down -22.5 dB at 20 kHz, relative to +12 dB at 6.3 kHz).

• TU-R (CCIR) ARM-weighting or ITU-R (CCIR) 2 kHz-weighting This curves derives from the ITU-R 468-curve above. Dolby Laboratories proposed using an average-response meter with the ITU-R 468-curve instead of the costly true quasi-peak meters used by the Europeans in specifying their equipment. They further proposed shifting the 0-dB reference point from 1 kHz to 2 kHz (in essence, sliding the curve down 6 dB). This became known as the ITU-R ARM (average response meter), as well as the ITU-R 2 kHz-weighting curve. (See: R. Dolby, D. Robinson, and K. Gundry, "A Practical Noise Measurement Method," J. Audio Eng. Soc., Vol. 27, No. 3, 1979) [Before using these terms be aware that the ITU-R, even after 20 years, takes strong exception to having its name used by a private company to promote its own methodologies.]

• Z-weighting A new term defined in IEC 61672-1, the latest international standard for sound pressure level measurements. It stand for zero-weighting, or no weighting; i.e., a flat measurement with equal emphasis of all frequencies.

Wendel -The name given by Steely Dan's famous recording engineer, Roger Nichols, for the sampling sequencer that he built in 1978 for their hit song, "Hey Nineteen."

Wente, Edward Christopher (b.1889-19??) American engineer who invented the first condenser microphone in 1916 while working for Western Electric.

wet - (1) The result of mixing the original recorded sound with the processed sound (reverb, chorusing, doubling, etc. (2) Any sound with significant reverberation; not dead. Contrast with dry.

wet circuit - (See below)

wetting - (1) The free flow of solder alloy, with proper application of heat and flux, on a metallic surface to produce an adherent bond. (2) Wetted relay contacts prevent damaging chemicals such as oxides and hydrocarbons from forming on the contacts. The build-up increases the contact resistance which can cause a voltage drop and/or heating of the contacts. (2) The practice of wetting reed relay contacts with mercury; called mercury-wetted relay.

wet transformer - An analog audio transformer designed for both DC and AC operation. Derived from the term, wet circuit, referring to a circuit where voice signals are transmitted and also carries direct current. Contrast with dry transformer.

WFAE - (World Forum for Acoustic Ecology) "An interdisciplinary spectrum of individuals engaged in the study of the scientific, social, and cultural aspects of natural and human made sound environments."

WFS - (wave field synthesis)

WFX - Worship facilities conference & expo that brings together three church groups: Church Leaders, Technology Gurus, and Facilities Managers and teams.

whammy bar - Nickname for the metal handle contraption found on some electric guitars that allows the player to momentarily change the tension (or actually stretch) the strings in order to create a vibrato effect (often mistakenly called a tremolo device).

Wheatstone bridge - An instrument used for measuring resistance. The circuit used is a 4-arm bridge, all arms of which are predominantly resistive. The bridge is a two-port network (i.e., it has two terminal pairs across opposite corners) capable of being operated in such a manner that when voltage is applied to one port, by suitable adjustment of the resistive elements in the network, zero output can be obtained at the signal output port (usually a meter). Under these circumstances the bridges is termed balanced. [Although the circuit used in a Wheatstone bridge was first described by Samuel Hunter Christie (1784-1865) -- the son of James Christie, founder of the well-known auction house -- in his paper "Experimental Determination of the Laws of Magneto-electric Induction" (1833), Sir Charles Wheatstone (1802-1875) received credit for its invention because of his adaptation of the circuit in 1843 for the measurement of resistance. Wheatstone also invented the concertina, the stereoscope and contributed significantly to the development of the telegraph.]

whistle or whine - Terms for noise in the 500 Hz to 2 kHz range. [Things like air conditioners and diffusers.]

white label - New twelve-inch vinyl singles with plain white labels used by record companies and DJs for their advance promotional copies.

Whitelabel.net - Free promotional download site for DJs and record labels for use with Rane/Serato Scratch Live systems.

white noise - (1) Analogous to white light containing equal amounts of all visible frequencies, white noise contains equal amounts of all audible frequencies (technically the bandwidth of noise is infinite, but for audio purposes it is limited to just the audio frequencies). From an energy standpoint white noise has constant power per hertz (also referred to as unit bandwidth), i.e., at every frequency there is the same amount of power (while pink noise, for instance, has constant power per octave band of frequency). A plot of white noise power vs. frequency is flat if the measuring device uses the same width filter for all measurements. This is known as a fixed bandwidth filter. For instance, a fixed bandwidth of 5 Hz is common, i.e., the test equipment measures the amplitude at each frequency using a filter that is 5 Hz wide. It is 5 Hz wide when measuring 50 Hz or 2 kHz or 9.4 kHz, etc. A plot of white noise power vs. frequency change is not flat if the measuring device uses a variable width filter. This is known as a fixed percentage bandwidth filter. A common example of which is 1/3-octave wide, which equals a bandwidth of 23%. This means that for every frequency measured the bandwidth of the measuring filter changes to 23% of that new center frequency. For example the measuring bandwidth at 100 Hz is 23 Hz wide, then changes to 230 Hz wide when measuring 1 kHz, and so on. Therefore the plot of noise power vs. frequency is not flat, but shows a 3 dB rise in amplitude per octave of frequency change. Due to this rising frequency characteristic, white noise sounds very bright and lacking in low frequencies. [Here's the technical details: noise power is actually its power density spectrum - a measure of how the noise power contributed by individual frequency components is distributed over the frequency spectrum. It should be measured in watts/Hz; however it isn't. The accepted practice in noise theory is to use amplitude-squared as the unit of power (purists justify this by assuming a one-ohm resistor load). For electrical signals this gives units of volts-squared/Hz, or more commonly expressed as volts/root-Hertz. Note that the denominator gets bigger by the square root of the increase in frequency. Therefore, for an octave increase (doubling) of frequency, the denominator increases by the square root of two, which equals 1.414, or 3 dB. In order for the energy to remain constant (as it must if it is to remain white noise) there has to be an offsetting increase in amplitude (the numerator term) of 3 dB to exactly cancel the 3 dB increase in the denominator term. Thus the upward 3 dB/octave sloping characteristic of white noise amplitude when measured in constant percentage increments like 1/3-octave.]

white space - Term for the theoretically unused frequency spectrum separating analog TV channels. While unused in theory, it is in fact where pro audio wireless microphones and monitors operate.

whole tone or whole step - Two notes spaced 1/6 octave apart. Contrast with semitone.

Wicks, Charlie -(b. 1945-2010) American entrepreneur best remembered as the founder of Pro Co Sound company and his self-proclaimed title: Captain of the Universe.

wide-range curve - Same as X curve.

Widlar, Bob - (b. 1937-1991) Famous eccentric American engineer, pioneer linear IC designer who created the first op amp ICs among many other IC innovations.

Wi-Fi - (wireless fidelity) Shorten form for the Wi-Fi Alliance, a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specification. Wi-Fi Certification results from testing 802.11-based wireless equipment to make sure it meets the Wi-Fi standard and works with all other manufacturers' Wi-Fi equipment on the market.

windshield - Slang for a pop filter.

Wintel - A contraction of the words "Windows" and "Intel." Used to describe personal computers made from Intel microprocessors and running Microsoft Windows software. It is reported that this "Wintel standard" accounts for 80% of all PCs.

wiring classes - U.S. National Electrical Code (NEC) defines three classes of wiring according to their fire and shock hazard potential:

Class 1 Where both fire and shock hazards exist, i.e., the wiring can deliver enough current for a fire hazard and enough voltage for a shock hazard. The most common example is AC power running to equipment. This class requires prevention of all touching and barriers against fire.

Class 2 Where neither fire or shock hazard exists, i.e. the wiring cannot deliver enough current (internal limiting) for a fire hazard and not enough voltage for a shock hazard. Examples here are all normal audio interconnect plus most power amplifier output wiring.

Class 3 Where there is not a fire hazard but there is a shock hazard, i.e., the wiring cannot deliver enough current (internal limiting) for a fire hazard, but can deliver enough voltage for a shock hazard. Requires touch-proof terminals; seen in audio for very high-output power amplifiers.

WLAN - (wireless local area network) See Wi-Fi for example.

WOM - (write-only-memory) Term coined by Signetics in 1972 for their 25000 Series 9046XN Random Access Write-Only-Memory integrated circuits. Based on SEX (Signetics EXtra secret) processes, these devices employ both enhancement and depletion mode P-Channel, N-Channel, and NEU-Channel MOS transistors (devices which simultaneously, randomly, or not at all, enhance or deplete regardless of gate polarity). The world's supply of WOMs was quickly consumed by newly designed airline baggage-handling equipment, where they are still used today to store the exact real-time location of each bag. WOM production was suddenly discontinued when it was discovered that the only copy of the mask code had been accidentally filed into a WOM location.

woofer - Low-frequency loudspeaker.

word - An ordered set of bits that is the normal unit in which information may be stored, transmitted, or operated upon within a given computer -- commonly 16 or 32 bits.

word clock - The synchronizing signal that indicates the sampling frequency or rate of sample words over a digital audio interface.

word length - The number of bits in a word.

work - The scalar product of the force on a body and the displacement of the body. In simpler terms, it is force on a body times the distance the body moves in the direction of the force. The symbol for work is W and its SI unit is the joule (J).

World Wide Web - (WWW and/or W3) (1) A way to present resources and information over the Internet, or according to its inventor, British scientist Tim Berners-Lee, while at CERN in 1989, "The World Wide Web (W3) is the universe of network-accessible information, an embodiment of human knowledge."

WORM or WOROM - (write-once read-only memory) Systems in which data may be written once, but not erased and rewritten. Usually refers to CD-ROM technology that can be recorded once only.

wow A form of distortion due to very slow (~ 1 Hz) variations in rotational speed common to turntables and analog tape recorders. Heard as a slow variation in the pitch when played back. Compare with flutter.

WPAN - (wireless personal-area network) For instance, see Bluetooth and ZigBee.

Write - To record data on a medium.

WWW - (World Wide Web) See World Wide Web.

wye connector - See Y-connector.

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HistoryOfRecording.com acknowledges the Elsevier, Inc. publication, Audio Engineering know it all, the University of Washington Press publication, The Audio Dictionary, second edition, the Howard W. Sames & Co., Inc. publication, Audio cyclopedia, the Cambridge University Press publication, The Art of Electronics, Rane Corporation (Dennis A. Bohn, CTO), Houghton Mifflin Company publication, The American Heritage Dictionary of the English Language, Fourth Edition, the IEEE publication, IEEE 100: The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition and Wikipedia in the preparation of this Dictionary of Audio Terminology.

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