Dictionary of Audio Terminology - F
fa - The fourth tone of the diatonic scale in solfeggio. [AHD]
facetious - One of the words that contain all five vowels in the correct order. Other examples are obscure scientific terms.
fader - A control used to fade out one input source and fade in another. The fading of a single source is called attenuation and uses an attenuator.
fado - (1) Portuguese musical genre. (2) A sad Portuguese folksong. [AHD]
Fahnestock clip - A type of spring-clip terminal for electrical wire that is one of the oldest and most popular ever made.
Fahrenheit Abbr. F - Of or relating to a temperature scale that registers the freezing point of water as 32 °F and the boiling point as 212 °F, under normal atmospheric pressure. [AHD]
Fahrenheit, Gabriel Daniel (b. 1686-1736) German-born physicist who invented the mercury thermometer (1714) and devised the Fahrenheit temperature scale. [AHD]
Fairchild 670 Compressor Limiter - Designed by Rein Narma in 1959, while at Fairchild Recording Equipment Company in Long Island City, NY. The most revered pro audio compressor.
Fairchild, Sherman Mills - (b. 1896 - 1971) American inventor and entrepreneur who founded many companies, the most famous of which were Fairchild Recording and Fairchild Semiconductor.
fall time - The time required for a signal to decay from 90 % to 10 % of its maximum amplitude.
fandango - An animated Spanish or Spanish-American dance in triple time.
FAQ (frequently asked question) - Acronym commonly seen on bulletin boards, Internet Web sites, and corporate information centers. By compiling FAQ lists (FAQs), organizations significantly reduce time spent repeatedly answering the same questions.
farad Abbr. F - The unit of capacitance in the meter-kilogram-second system equal to the capacitance of a capacitor having an equal and opposite charge of 1 coulomb on each plate and a potential difference of 1 volt between the plates. [AHD] [After Michael Faraday.]
Faraday, Michael - (b. 1791-1867) British physicist and chemist who discovered electromagnetic induction (1831) and proposed the field theory later developed by Maxwell and Einstein. [AHD]
Faraday Effect or Kerr Effect - If an isotropic dielectric is placed in an electric field and a beam of light is passed through the sample orthogonally to the field then the material displays birefringence. This forms the basis of recordable optical discs.
far end - Teleconferencing term meaning the distant location of transmission; the other end of the telephone line, as opposed to your end (known as the near end).
far-end crosstalk - Crosstalk that is propagated in a disturbed channel in the same direction as the propagation of the signal in the disturbing channel. The terminals of the disturbed channel, at which the far-end crosstalk is present, and the energized terminals of the disturbing channel, are usually remote from each other.
far field or far sound field - The sound field distant enough from the sound source so the SPL decreases by 6 dB for each doubling of the distance from the source (inverse square law). Contrast with near field.
Fast Ethernet – Data speeds up to 100 Mbps, and "1000Base-T" up to 1 gigabit/sec, or 1000 Mbps, aka Gigabit Ethernet (GE) [uses all 8 conductors and can be up to 100 meters long].
fat - Informal phrase for heavily processed audio, usually featuring lots of reverb, chorusing, or doubling. Also seen as phat sound.
fax on demand - One of the terms for the process of ordering fax documents from remote machines via telephone, using a combination of voice processing and fax technologies. Also called fax-back.
FDTD (finite difference time domain) - A numerical technique for solving a partial differential equation involving time and space variables. The solution is implemented sequentially in the time domain. [IEEE]
FEA (Finite Element Analysis) - A computer-based numerical technique for calculating the strength and behavior of engineering structures.
feedback In reference to acoustics, the phenomenon where the sound from a loudspeaker is picked up by the microphone feeding it, and re-amplified out the same loudspeaker only to return to the same microphone to be re-amplified again, forming an acoustic loop. Each time the signal becomes larger until the system runs away and rings or feeds back on itself producing the all-too-common scream or squeal found in sound systems. These buildups occur at particular frequencies called feedback frequencies.
feedback - In reference to electronics, the return of a portion of the output of a process or system to the input, especially when used to maintain performance or to control a system or process. [AHD]
Feedback Stability Margin - The acoustic gain safety margin for a sound system to minimize acoustic feedback problems, usually set at 6 dB.
feedback suppressor - An audio signal processing device that uses automatic detection to determine acoustic feedback frequencies and then positions notch filters to cancel the offending frequencies. Other methods use continuous frequency shifting (a very small amount) to prevent frequency build up and feedback before it happens.
feed-through hole or vias – On printed circuit boards, a pad with a plated-through hole connecting one layer to another.
FDDI (fiber distributed data interface) - An ANSI standard describing a 100 megabytes/sec (MBps) fiber optic LAN; now also specified for twisted-pair use.
femto - Prefix for one thousandth of one trillionth (10-15), abbreviated f.
Fender, Clarence Leonidas "Leo" - (b. 1909-1991) American inventor and entrepreneur who founded the Fender Electric Instrument Company in 1946 and invented the legendary Stratocaster and Telecaster guitars.
ferrite - (1) Any of a group of nonmetallic, ceramic-like, usually ferromagnetic compounds of ferric oxide with other oxides, especially such a compound characterized by extremely high electrical resistivity and used in computer memory elements, permanent magnets, and various solid-state devices. (2) Iron that has not combined with carbon, occurring commonly in steel, cast iron, and pig iron below 910°C. [AHD]
ferrite bead - A small toroidal shaped part made from a mixture of iron, nickel and zinc oxides used to suppress EMI in audio and other electronic equipment. Usually seen on the inputs and outputs of equipment, ferrite beads act electrically like an inductor in series with a resistor.
FET (field-effect transistor) - A three-terminal transistor device where the output current flowing between the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide semiconductor FET). Each type has two polarities: positive, or p-channel devices, and negative, or n-channel devices. In a JFET device the gate forms a true semiconductor junction with the channel, while in a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
FFL (flat flexible loudspeaker) - Loudspeaker technology developed by Warwick Audio Technologies, a spin-off company from The University of Warwick School of Engineering.
FFT (fast Fourier transform) - (1) Similar to a discrete Fourier transform except the algorithm requires the number of sampled points be a power of two. (2) A DSP algorithm that is the computational equivalent to performing a specific number of discrete Fourier transforms, but by taking advantage of computational symmetries and redundancies, significantly reduces the computational burden.
fiber optics - The technology of using glass fibers to convey light and modulated information. Short distances (typically less than 150 feet) use plastic fibers, while long distances must use glass fibers.
Fidelipac (aka NAB cartridge or simply 'cart') - Magnetic tape recording format that became the industry standard for radio broadcasting, introduced in 1959.
field - In reference to video, one half of a complete video scanning cycle, equaling 1/60 second, or 16.67 milliseconds for NTSC and 1/50 second, or 20 milliseconds for PAL/SECAM.
field - In reference to mathematics, a set of elements having two operations, designated addition and multiplication, satisfying the conditions that multiplication is distributive over addition, that the set is a group under addition, and that the elements with the exception of the additive identity form a group under multiplication. [AHD]
figure-of-eight - A bidirectional microphone or one that responds equally front and rear and not at all to side sounds.
filament - The heating element in a vacuum tube.
filter - Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others.
FinFet (fin field-effect transistor) - The term was coined by University of California, Berkeley researchers (Profs. Chenming Hu, Tsu-Jae King-Liu and Jeffrey Bokor) to describe a nonplanar, double-gate transistor built on an SOI substrate. [Huang, X. et al. (1999) "Sub 50-nm FinFET: PMOS" International Electron Devices Meeting Technical Digest, p. 67. December 5–8, 1999]
Finite Element Analysis Abbr. FEA - A computer-based numerical technique for calculating the strength and behavior of engineering structures.
finite field (aka Galois field) - A field with a finite number of elements.
fipple - (1) A whistle like mouthpiece for certain wind instruments, such as a recorder or flageolet, that channels the breath toward the sounding edge of a side opening. (2) An object similar to a fipple in an organ pipe. [AHD]
FIR (finite impulse-response) filter - A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs. An FIR filter can be designed to have linear phase (i.e., constant time delay, regardless of frequency). FIR filters designed for frequencies much lower that the sample rate and/or with sharp transitions are computationally intensive, with large time delays. Popularly used for adaptive filters.
Firefly - A low-cost, low-power, two-way, wireless communications standard between compliant devices anywhere in and around the home (automation, toys, PC peripherals, etc.), developed by Philips and others.
Firewire or IEEE 1394 - A joint Apple and TI implementation of the IEEE P1394 Serial Bus Standard. It is a high-speed (100/200/400 Mbits/sec now, with 1 Gbit/s on the horizon) serial bus for peripheral devices
firmware - Computer read-only memory (ROM) code (files) residing inside DSP and microprocessor ICs that controls the hardware response to software instructions -- the liaison between software and hardware. Now really a specific type of software since most firmware updates are done via some sort of streaming network rather than burning new hardware ROMS.
fishpaper - An insulating paper, often fiber- or oilcloth-like, used in the construction of transformers and coils.
fixed-point - A computing method where numbers are expressed in the fixed-point representation system, i.e., one where the position of the "decimal point" (technically the radix point) is fixed with respect to one end of the numbers. Integer or fractional data is expressed in a specific number of digits, with a radix point implicitly located at a predetermined position. Fixed-point DSPs support fractional arithmetic, which is better suited to digital audio processing than integer arithmetic. A couple of fixed-point examples with two decimal places are 4.56 and 1789.45.
FLAC (free lossless audio codec) - A lossless compression standard for music files.
flanging - Originally, "flanging" was achieved using two reel-to-reel tape recorders playing the same program, in synchronization, with their outputs summed together. By alternately slowing one machine, then the other, different phase cancellations occurred in the summation process. The "slowing down" was done simply by pressing against the flanges of the tape reels, hence the original term "reel flanging," soon shortened to just "flanging." Since the two identical signals would alternately add and subtract due to the introduced phase (timing) difference, the audible effect was one of a sweeping comb filter. It was described as a "swishing" or "tunneling" sound. Soon electronic means were devised to mimic true "reel flanging" by using delay lines and mixing techniques. Adding a low-frequency oscillator to modulate the audio delay line's clock signal created a sweeping effect, much like a jet airplane taking off. The best flangers used two delay lines. Compare with phaser
Fleming, Sir John Ambrose - (b. 1849-1945) British electrical engineer and inventor known for his work on electric lighting, wireless telegraphy, and the telephone. He invented and patented the first tube, a diode (which he called a thermionic valve, he used for signal detection (although Edison technically developed the first tube with a version of his light bulb).
Fletcher, Harvey - (b. 1884-1981) American physicist and legendary pioneer in acoustics and hearing most often associated with the Fletcher-Munson Curves below. He published his findings in his book, Speech and Hearing (Van Nostrand Co., 1929). [And H. D. Arnold wrote the introduction.]
Fletcher-Munson Curves - In the '30s, researchers Fletcher and Munson first accurately measured and published a set of curves showing the human's ear's sensitivity to pure tone loudness verses frequency ("Loudness, its Definition Measurement and Calculation," J. Acoust. Soc. Am., vol. 5, p 82, Oct. 1933). They conclusively demonstrated that human hearing is extremely dependent upon loudness. The curves show the ear most sensitive to pure tones in the 3 kHz to 4 kHz area. This means sounds above and below 3-4 kHz must be louder in order to be heard just as loud. For this reason, the Fletcher-Munson curves are referred to as "equal loudness contours." They represent a family of curves from "just heard," (0 dB SPL) all the way to "harmfully loud" (130 dB SPL), usually plotted in 10 dB loudness increments.
flicker - In reference to AC power systems, the effect caused when load switching creates a short-duration dip in the AC voltage, as when the lights dim momentarily when the refrigerator compressor kicks in.
flicker noise or 1/f noise - Noise whose amplitude varies inversely with frequency. Mainly used in solid-state physics to describe noise with 1/f behavior, such as the noise resulting from impurities in the conducting channel, generation and recombination noise due to base current in transistors, etc. Pink noise has a 1/f characteristic so the two terms are often interchanged, however when used to describe semiconductor noise (in op amps for instance) it is uniquely a low-frequency phenomena occurring below 2 kHz, while in audio, pink noise is wideband to 20 kHz.
floating-point - A computing method where numbers are expressed in the floating-point representation system, i.e., one where the position of the decimal point does not remain fixed with respect to one end of numerical expressions, but is regularly recalculated. A floating-point number has four parts: sign, mantissa, radix, and exponent. The sign indicates polarity so it is always 1 or -1. The mantissa is a positive number representing the significant digits. The exponent indicates the power of the radix (i.e., the number base, usually binary 2, but sometimes hexadecimal 16). A common example is the "scientific notation" used in all science and mathematics fields. Scientific notation is a floating point system with radix 10 (i.e., decimal).
floating unbalanced 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.
FLOPS (floating-point operations per second) - A measure of computing power.
flutter - (1) Any significant variation from the designed study rotational speed of a recording or playback mechanism, e.g., turntables and analog tape recorders (typically at 5-10 Hz rate). Heard as rapid fluctuation in pitch when played back. Compare with wow. (2) In reference to telecommunications, any rapid variation of signal parameters, such as amplitude, phase, and frequency.
flutter echo - An acoustic effect in some rooms where sound is reflected back and forth between two parallel surfaces, such as opposite walls. In order to qualify as a flutter echo the reflections must be fewer than about 15 or so per second. This happens when the walls are more than about 25 feet apart. Parallel surfaces closer than this give rise to standing waves that result in nonuniform distribution of sound between the surfaces. [White]
flux - The lines of force found in an electric or magnetic field.
fluxivity - The recorded flux per unit track width.
flux unit or jansky Abbr. Jy - A unit of spectral power flux density: 10-26 times one watt per square meter per Hertz (IEEE Std 211).
FM (frequency modulation) The encoding of a carrier wave by variation of its frequency in accordance with an input signal. [AHD]
FOH - Abbreviation for front of house, used to describe the main mixer usually located in the audience for sound reinforcement systems. Meant to differentiate the main house mixer from the monitor mixer normally located to the side of the stage.
foldback - The original term for monitors, or monitor loudspeakers, used by stage musicians to hear themselves and/or the rest of the band. The term "monitors" has replaced "foldback" in common practice.
Foley - A term synonymous with film sound effects. A recording studio Foley stage is where the sound effects are generated in synch with the moving picture.
follower Shortened form for a number of electronic circuit buffer amplifiers named voltage followers, cathode followers, emitter followers, etc.
Fonz Foot WedgeA special floor monitor developed for the Dave Matthews Band that utilizes a tactile transducer (like the one found in drummers butt thumpers) to produce a tactile pounding on the musicians foot.
foreground music - Officially music with (or without) lyrics and performed by the original artist. Used where it is believed people will pay attention to it. Contrast with background music.
form factor - The ratio of RMS value to average value for an alternating current waveform.
forward masking - Masking of a later arriving signal due to an earlier one. The effects of a loud first sound can last long enough to mask a later arriving softer one (periods less than 500 ms and greater than 10 dB loudness differences).
Fourier analysis - Most often the approximation of a function through the application of a Fourier series to periodic data, however it is not restricted to periodic data.
Fourier, Baron Jean Baptiste Joseph - (b. 1768-1830) French mathematician and physicist who formulated a method for analyzing periodic functions and studied the conduction of heat. [AHD]
Fourier series - Application of the Fourier theorem to a periodic function, resulting in sine and cosine terms which are harmonics of the periodic frequency.
Fourier theorem - A mathematical theorem stating that any function may be resolved into sine and cosine terms with known amplitudes and phases.
Fourier transform - A circuit analysis technique that decomposes or separates a waveform or function into sinusoids of different frequency which sum to the original waveform. It identifies or distinguishes the different frequency sinusoids and their respective amplitudes [Brigham, E. Oren, The Fast Fourier Transform and Its Applications, Englewood Cliffs, NJ: Prentice-Hall, Inc., 1988.]
FPGA (field-programmable gate array) - A programmable logic device which is more versatile than traditional programmable devices such as PALs and PLAs.
fps (frames per second) - Frame rate is expressed as frames per second, abbreviated fps.
FracRack (Fractional Rack) - Nickname for 3U high 19" wide powered rack designed to accommodate modular synthesizer modules available from many manufacturers. First introduced by PAiA, called FracRak™. Similar to Eurorack with minor (but important) differences.
frame - One complete video scanning cycle, equals two fields for NTSC and PAL/SECAM. Also frame rate is expressed as frames per second, abbreviated fps.
frame - A element of Ethernet systems made up of three elements: two addresses, the data, and an error checking field.
frammel - In arrays it is sometimes necessary to separate and angle the cabinets a small amount to reduce phase interference. This is often done using a narrow wood strip called a frammel.
FRAP (flat response audio pick-up) - A type of piezoelectric pick-up developed by Arnie Lazarus in the late '60s.
Freed, Alan - (b. 1921-1965) Famous American radio disc jockey who jump-started the rock 'n' roll revolution that shook up the last half of the 20th century.
free field or free sound field - A sound field without boundaries or where the boundaries are so distant as to cause negligible reflections over the frequency range of interest.
frequency – (1) The property or condition of occurring at frequent intervals. (2) The number of times a specified phenomenon occurs within a specified interval, as: (a) The number of repetitions of a complete sequence of values of a periodic function per unit variation of an independent variable. (b) The number of complete cycles of a periodic process occurring per unit time. (c) The number of repetitions per unit time of a complete waveform, as of an electric current. [AHD]
frequency bands - Broadcast transmission frequency bands are broken into groups as follows:
• HF (high frequency) 3 MHz to 30 MHz
• VHF (very high frequency) 30 MHz to 300 MHz
• UHF (ultra high frequency) 300 MHz to 3 GHz
• SHF (super high frequency) 3 GHz to 30 GHz
• EHF (extremely high frequency) 30 GHz to 300 GHz
frequency modulation (FM) - Encoding of a carrier wave by variation of its frequency in accordance with an input signal. [AHD]
frequency-modulation (friction) noise - Frequency modulation of the signal in the range above approximately 100 Hz resulting in distortion which may be perceived as a noise added to the signal (that is, a noise not present in the absence of a signal). [IEEE]
frequency response - It connotes amplitude-frequency response and quantifies a device's maximum and minimum frequency for full-output response. The electrical passband of an audio device. The measure of any audio device's ability to respond to a sine wave program, and therefore is a complex function measuring gain and phase shift (see phasor). It is used to express variation of gain, loss, amplification, or attenuation as a function of frequency, normally referred to a standard 1 kHz reference point.
frequency shift keying Abbr. FSK - A modulation technique in which binary 0 and 1 are represented by two different frequencies. [IEEE]
friction noise - Frequency modulation of the signal in the range above approximately 100 Hz resulting in distortion which may be perceived as a noise added to the signal (that is, a noise not present in the absence of a signal). [IEEE]
Frying Pan - The first electric guitar, developed in 1931.
FSK (frequency shift keying) - A modulation technique in which binary 0 and 1 are represented by two different frequencies. [IEEE]
FSM (Feedback Stability Margin) - The acoustic gain safety margin for a sound system to minimize acoustic feedback problems, usually set at 6 dB.
full duplex or duplex - Pertaining to a simultaneous two-way independent transmission in both directions.
full-range - Any audio device capable of capturing, reproducing or processing the full audio frequency spectrum of 20 Hz to 20 kHz.
full-wave rectification - Term used to describe a rectifier that inverts the negative half-cycle of the input sinusoid so that the output contains two half-sine pulses for each input cycle. [IEEE]
fundamental - In reference to music, the first harmonic in a harmonic series; the lowest harmonic. In reference to physics, the lowest frequency of a periodically varying quantity or of a vibrating system. [AHD]
fuzz box also fuzzbox - One of the earliest guitar effects units made popular in the '60s psychedelic and heavy metal sound. Early fuzz boxes were not much more than a heavy clipped signal, which tends to sound clarinet-like due to it squaring up the signal which adds lots of odd harmonics characteristic of the clarinet.
fuzzy clustering - Analysis technique where complex problems are divided into groups or "clusters" for easier understanding. When the division between clusters is not sharp then you have "fuzzy" clusters that more accurately model real life situations. The importance to pro audio comes from it's use in modeling acoustic fields to predict SPL and other phenomena.
F-wrench - Slang term for vernier calipers due to their resemblance to the letter "F."
FX unit - Slang for "effects unit."
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