Audio Glossary of Terms

• Accessory (position) - Refers to the position of the key in the ignition switch; A wire showing 12 Volts (+) when in this position.
 
 
 
• Acoustic Absorption  -The sound deadening properties of any substance, measured in sabine units. One sabine is equal to the absorption of 1 square foot of surface which will absorb all incident energy. 
 

 
 
• Acoustic Feedback - A squealing sound when the output of an audio circuit is fed back in phase into the circuit's input.
 
 
 
• Acoustics - The study of sound. The science of production, effects, and transmission of sound waves through various mediums and the effects of absorption, diffraction, interference, reflection, and refraction.
 
 
 
• Aliasing Noise - The result of the sampling frequency not being at least double the highest analog frequency during the digital encoding of an analog signal.
 
 
 
• Alternate-Channel Selectivity - A measurement of a tuner's ability to select one radio station's signal and reject the signal of another radio station two channels (0.4 Mhz) away. Measured in decibels, the higher the number the better.
 
 
 
• Alternating Current (AC) - An electric current that reverses direction at regular intervals. Measured in Volts AC at Hertz, example: 110 volts AC 60 Hz.
 
 
 
• American Wire Gauge (AWG) - A standard of the dimensional characteristics of wire used to conduct electrical current or signals. AWG is identical to the Brown and Sharpe (B & S) wire gauge.
 
 
 
• Ammeter - An instrument that measures the magnitude of an electric current in amperes.
 
 
 
• Ampere (amp) - A unit that defines the rate of flow of electricity (current) in a circuit.
 
 
 
• Amplification - The increase in signal level, amplitude or magnitude.
 
 
 
• Amplifier - 1 A device which increases the level of a signal by increasing the current or voltage. 2 May also be used to isolate or control a signal and even decrease the level as in a line output converter.
 
 
 
• Amplifier, Power - An amplifier designed for driving loudspeakers and having a higher power output than a line amplifier or preamplifier.
 
 
 
• Amplitude - The maximum value of a periodically varying quantity.
 
 
 
• Amplitude Modulation (AM) - The encoding of a carrier wave by variation of it's amplitude in accordance with an input signal. AM Stereo
 
 
 
• Analog - A way to represent data by means of continuously variable quantities. A control or circuit which continuously changes the level of a signal in direct relationship to the control setting. An electrical signal whose frequency and level vary continuously in direct relationship to the original acoustical sound waves. (something that is analogous)
 
 
 
• Analog to Digital Convertor (ADC) - A circuit that converts an analog signal into a digital signal. With a continuous input signal the ADC will check the signal several time per second (sampling), assign values to the samples and represent it as a binary number (quantization and encoding).
 
 
 
• Analogous - Alike in certain ways. Similar in function but not in origin or structure.
 
 
 
• Antenna - An apparatus used for sending and receiving radio waves, usually constructed of metal.
 
 
 
• Antenna Trimmer - An adjustment found on analog radios used to maximize AM reception. Turning this trimmer to the point where the sound is the loudest increases the sets signal to noise ratio optimizing performance.
 
 
 
• Attenuator - A device to decrease or increase the strength of a signal.
 
 
 
• Auto Eject - Feature of a cassette player that ejects the tape when it has finished playing one side.
 
 
 
• Auto Loud - Automatically provides low frequency boost for listening at low levels.
 
 
 
• Auto Replay - Feature of a cassette player that automatically rewinds a tape when it has reached the end of one side, then begins to replay.
 
 
 
• Auto Reverse - Feature of a cassette player that automatically plays the reverse side of a tape when one side has reached the end.
 
 
 
• Auto Stop - Feature of a cassette player that automatically shuts off power when a tape has reached the end of either side in any mode.
 
 
 
• Automatic Gain Control (AGC) - A circuit that continuously adjust the recording amplifier gain to maintain a relatively constant recording level.
 
 
 
• Azimuth - The perpendicular alignment of the tape to the head of a tape player / recorder.

• Balance - The relative volume level between two channels, usually the left and right channels. May also refer to the relative volume between front and rear channels of an audio system. To make the same or equal.
 
 
 
• Balls - The strength or power to perform it's task extremely well without loss of performance even when pushed to it's limits.
 
 
 
• Bandpass - A two-part filter that cuts both high and low frequencies allowing the band of frequencies between these two points to pass.
 
 
 
• Bandwidth - The range of frequency response between lower and upper frequencies points which audio signals pass through an electrical device or conductor where the signal has rolled off by three decibels.
 
 
 
• Basket - The rigid frame of a speaker that supports all of it's components.
 
 
 
• Bass - The low audio frequency range typically below 500 Hz (hertz).
 
 
 
• Bi-Amplification - The use of two amplifiers, one for the amplification of lower (bass) frequencies , and the other for higher (midrange and treble) frequencies. The audio signal from the head unit or pre-amplifier is passed through an electronic crossover and divided into two separated signals. These signals are sent to the respective amplifiers and their outputs are sent to the respective speakers.(bass to woofers, midrange and treble to mids and tweeters through the use of passive crossovers) Tri-Amp is the use of three amplifiers in the same manner with the audio signal divided into three separate bands of frequency by the electronic crossover and so on.
 
 
 
• Bias - A necessary high frequency current applied to the record head along with the audio signal to prevent distortion and increase sensitivity during recording.
 
 
 
• Binary Digit (BIT) - The smallest unit of data in a digital signal represented by either a one or zero.
 
 
 
• Boom, Boomy - Excessive bass response or peak in bass response of a recording, playback, or sound system. Dominant in the low frequency range. Without complimentary levels of frequencies other than bass.
 
 
 
• Boost - To Increase.
 
 
 
• Bottom End - Bass response; referring to the sound qualities of the lowest frequency ranges of a speaker or audio system.
 
 
 
• Bridging - Combining two outputs of an amplifier to use as one, usually to a woofer. The provides an increase in power output (wattage) necessary to reproduce lower frequencies at higher volume levels.
 
 
 
• Brown and Sharp Gauge(B & S Gauge) - A standard of the dimensional characteristics of wire used to conduct electrical current or signals. B & S Gauge is identical to the American Wire Gauge (AWG).
 
 
 
• Buffer - Commonly found in Mini Disc (MD) and Compact Disc (CD) players, this device protects against vibrations by storing the audio data for uninterrupted playback. Data is available from the buffer when it can not be read from the disc so long as the interruption of reading the disc does not exceed the playback time of the data stored in the buffer.
 
 
 
• Byte - Eight bits. It takes one byte to represent one letter of the alphabet.

• Capacitance - The ability of a conductor or dielectric to store electric charge.
 
 
 
• Capacitor - 1 (polarized) An electrical circuit element used to store charge temporarily, consisting in general of two metallic plates separated by a dielectric. 2 (non-polarized) A crossover component used to filter out lower frequencies and allow higher frequencies to pass.
 
 
 
• Capture Ratio - Expressed in decibels, with the smaller the number the better. The ratio of captured signals of different strength on the same frequency.
 
 
 
• Circuit - 1 Any closed path followed by electrical current. 2 A configuration of electrically or electromagnetically connected components or devices.
 
 
 
• Circuit Breaker - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Unlike a fuse a circuit breaker is resetable. Rated in amperes (amps).
 
 
 
• Clipping - Audible distortion that occurs when continuous power-to-peak power capabilities (headroom) are exceeded. "Turn it down!"
 
 
 
• Coaxial - A speaker composed of larger cone for low range frequencies and a smaller cone or tweeter for higher frequencies aligned on the same axis. A crossover network is necessary to route the proper signals to each driver. These may be passive (usually included). If the speakers are bi-amplified, an active crossover will be used to route the proper range of frequencies to the respective amplifier channels.
 
 
 
• Coil (Choke, Inductor) - A crossover component used to filter out higher frequencies and allow lower frequencies to pass.
 
 
 
• Conduction - The mode of heat transfer within a body or between bodies in contact with each other.
 
 
 
• Conductivity - he ability of a conductor to allow the passage of electrons, measured in the current per unit of voltage applied, shown in resistance.
 
 
 
• Cone - The most common shape for the radiating surface of a loudspeaker referred to as the part that moves the air.
 
 
 
• Constant 12 V (+) - A lead, wire, or connection point that shows positive 12 volts regardless of ignition key position or any other switch; Positive terminal of 12 volt battery.
 
 
 
• Continuity - The condition of being continuous.
 
 
 
• Cross Interleave Reed-Solomon Code (CIRC) - A combination of codes and interleaved data that make it possible to detect and correct errors in a compact disc system.
 
 
 
• Crossover Frequencies - The frequencies at which an active or passive crossover network divides audio signals, expressed in Hertz (Hz).
 
 
 
• Crossover Network - A unit that divides the audio spectrum into two or more frequency bands. The two types are active and passive.
 
 
 
• Crossover Point - Same as crossover frequency.
 
 
 
• Crosstalk (Channel Separation) - The amount of interference on one stereo channel caused by the leaking of the other stereo channel. The higher the rating in decibels (dB), the better the Channel Separation.
 
 
 
• Current - The rate of flow of electricity, measured in amperes (amps).

• Decade - A measurement equal to the low pass frequency being ten times the high pass frequency, which is relevant in a passive band pass crossover. The difference between 500 Hz and 5000 Hz is equal to 1 decade.
 
 
 
• Decibel (dB) - A unit of measurement for the ratio of loudness. The threshold of hearing is 0 dB. One dB SPL is the smallest audible difference in sound level.
 
 
 
• Detent Controls - A detent knob has precise click-stops at regular points to indicate how much the control has been turned up or down.
 
 
 
• Deutsche Industrie Normen (DIN) - German (European) industrial standards. DIN size refers to the stereo size that fits most European automobiles.
 
 
 
• Dielectric - An insulating material with low electrical conductivity.
 
 
 
• Digital Output - An output where the signal is in digital form to allow external processing before being converted to an analog signal.
 
 
 
• Digital Time Delay - A component that electronically delays the audio signals (in milliseconds) to provide surround type sound as well as compensate for speaker placements.
 
 
 
• Digital Time Delay Gain Control - The control that lets you select how much of the whole of the audio signal to be treated with digital time delay.
 
 
 
• Diode - An electrical circuit element that allows current to flow in one direction.
 
 
 
• Direct Current (DC) - An electrical current that flows in one direction.
 
 
 
• Directional / Directionality - The angle at which a speaker disperses sound. Higher frequencies are narrower than lower frequencies. Tweeters are more directional than woofers.
 
 
 
• Dispersion - Distribution of sound from a speaker.
 
 
 
• Distortion - Sound that is modified or changed in some way. Measured as a percentage of the whole signal.
 
 
 
• Dolby Noise Reduction - A patented noise reduction system that increases dynamic range and signal-to-noise ratio of Dolby encoded media.
 
 
 
• Dome - A convex speaker shape usually used for tweeters.
 
 
 
• Driver - Synonymous with loudspeaker. The term also refers to a loudspeaker being coupled to a horn for acoustic coupling and controlled dispersion of sound.
 
 
 
• Dynamic Noise Reduction (DNR) - A signal-processing circuit that reduces the level of high frequencies (hiss). Unlike Dolby Noise Reduction, DNR does not require processing during recording.
 
 
 
• Dynamic Range - The difference between the softest and loudest portions of sound that an amplifier or recorder can reproduce within an acceptable range of distortion. Expressed in decibels, the higher the number the better.

• Effect Loop - A signal path which allows an audio processor to be switched in and out of the signal path such as an equalizer.
 
 
 
• Efficiency - The ratio of energy output to total energy input, expressed as a percentage. With speakers, this refers to the ratio of total acoustic watts radiated to total electrical watts input.
 
 
 
• Electromagnetic Interference (EMI) - The interference caused by an electromagnetic field created by the flow of current.
 
 
 
• Electrostatic Loudspeaker - A speaker composed of two pieces of metallic foil separated by a sheet of dielectric unlike a cone and voice coil of a typical cone-type speaker.
 
 
 
• Equalization - The process of changing the frequency balance of a signal so acoustical energy is proportional to the electrical input (or any type of relative frequency adjustment).
 
 
 
• Equalizer - A component designed to alter the frequency balance of an audio signal.
 
 
 
• Exa (E) - A prefix meaning 1018 or 1,000,000,000,000,000,000

• Fader - The control that adjusts the relative volume levels of front and rear speakers in a four speaker system or the front and rear pre-amplifier outputs.
 
 
 
• Farad - The basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of charge with one volt across it.
 
 
 
• Fidelity - The term used to describe the accuracy of recording, reproduction, or general quality of audio processing.
 
 
 
• Filter - An active or passive circuit or device designed to block a certain frequency or range of frequencies.
 
 
 
• Flat Frequency Response - Term for a circuit or audio system which will pass audio signals that will vary by no more than ± 1 dB usually between 20 Hz and 20 kHz unless otherwise specified.
 
 
 
• Fletcher Munson Curves - The set of curves showing the human's ear's frequency sensitivity versus loudness, created by researchers Fletcher and Munson. The curves show the ear to be most sensitive to sounds between 3 kHz and 4 kHz (ear canal resonances).
 
 
 
• Floating Ground - Non-common grounding point.
 
 
 
• FM Stereo Separation - The FM tuner demodulator's ability to separate left and right channel signals of FM stereo broadcast. Measured in decibels, the higher the number the better.
 
 
 
• Focus Lens - The lens in the optical block of a compact disc player which focuses the laser light onto the surface of the disc.
 
 
 
• Focus Servo - The circuit which keeps the laser light correctly focused on the pit area of the disc.
 
 
 
• Frequency - The number of wavelengths which pass a specific point in a specific time period, measured in Hertz (Hz). Cycles per second.
 
 
 
• Frequency Dividing Network - See crossover network.
 
 
 
• Frequency Modulation (FM) - The encoding of a carrier wave by variation of it's frequency in accordance with an input signal.
 
 
 
• Frequency Response - The lowest and highest parts of the frequency spectrum that can be reproduced by an audio component within specific limits and tolerances.
 
 
 
• Fundamental Frequency - The principal component of a complex waveform having the lowest frequency.
 
 
 
• Fuse - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Rated in amperes (amps).

 
• Gain - The amount of amplification used in an electrical circuit.
 
 
 
• Gauge (wire) - The diameter of a wire. The higher the number, the thinner the wire.
 
 
 
• Giga - Prefix meaning 109 or 1,000,000,000 (1 billion in the US)
 
 
 
• Googol - A googol is the number 10100, that is, 1 followed by one hundred zeroes.
 
 
 
• Graphic (equalizer) - Refers to a type of equalizer with sliding controls that create a pattern representing a graph of frequency response changes.
 
 
 
• Ground - An electrical line with the same electrical potential as the chassis of the vehicle, most commonly negative 12 volts DC.
 
 
 
• Ground Loop - The condition created when two or more paths for electricity are created in a ground line, or when one or more paths are created in a shield or an audio cable. This can create undesirable noise such as a high pitched whine when the vehicle is running or pops and clicks when other devices are used in the vehicle.
 
 
 
• Ground Potential - In an automobile this is the electrical potential of the vehicles chassis, specifically the chassis of the alternator when the vehicle is running. A circuit, terminal or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.

• Henry / Henries (Hy) - The measurement for inductance. Coils (low pass filters) are measured in millihenries as in 6.4 mHy (6.4 millihenries).
 
 
 
• Hertz (Hz) - The unit of measurement for frequency. 1 Hz is equal to 1 cycle per second.
 
 
 
• High Frequency Driver - A loudspeaker specifically designed to reproduce short, high-frequency wave lengths. The driver typically has a small, lightweight diaphragm. Tweeter.
 
 
 
• High Pass Filter - A network of elements used to attenuate all frequencies below a predetermined frequency. Frequencies above the cutoff point pass without any effect.
 
 
 
• Highs - Term which refers to a set of speaker components used to reproduce frequencies above 500 Hz as in a set of separates. May also refer to tweeters which are used to reproduce frequencies usually above 2.5 kHz. Not bass.

• IASCA - International Auto Sound Challenge Association
 
 
 
• Image Rejection - The rejection of the same signals that can be received at two or more points on the dial of a tuner by a single radio station (ghost, images) . Image Rejection is expressed in decibels, the higher the number the better.
 
 
 
• Imaging - The reproduction of sound accurately so that the listener can imagine the original environment and placement of the original sound sources accurately within within that environment. The better the imaging the more analogous the reproduced sound will be to the original.
 
 
 
• Impedance - The opposition to the flow of alternating current (AC) in a circuit. Measured in ohms .
 
 
 
• Inductance - The ability to induce an electrical current. Measured in Henrys.
 
 
 
• Input Sensitivity Control - Adjusts the amount of input signal being fed to the amplifier stage to reduce distortion.
 
 
 
• Insulation - A material that electrically isolates a conductor or thermally isolates an object from its surroundings.
 
 
 
• Intermodulation Distortion (in loudspeakers) - Is the distortion generated in single cone speakers when the cone is reproducing a high and low frequency simultaneously. The high frequency peaks will be flattened off if the low frequency is distorted in any way.

 
• Jacket - The outer covering on a cable or wire that may provide electrical insulation and/or resistance to abrasion, chemicals, and moisture.
 
 
 
• Jams - Tunes, rocks, hits, sounds good, etc.
 
 
 
• Japanese Industrial Standards Committee (JISC or JIS) - A Japanese agency that establishes and maintains standards for equipment and components.
 
 
 
• Jewel Case - The hard plastic case that contains a compact disc.
 
 
 
• Junk - Discarded or useless; of no value.

 
• Kilo (k) - A prefix meaning thousand.
 
 
 
• Kilohertz (kHz) - 1 kHz equals one thousand hertz or 1,000 times per second. Formerly kilocycles (kc).

• Laser Diode - A semiconductor device which emits a laser beam.
 
 
 
• LED - Light emitting diode.
 
 
 
• Line Level - The standard preamplifier output level of a signal from an audio source other than a turntable. Usually between 100mV and 1V, but may be as high as 5V or more from some preamplifiers.
 
 
 
• Linearity Error - The deviation in response from an expected or theoretical straight line value for instruments and transducers (speakers).
 
 
 
• Liquid Crystal Display (LCD) - A type of digital display made of a material that changes reflectance or transmittance when an electrical field is applied to it.
 
 
 
• Load - The electrical demand of a process, expressed in current (amps), power (watts), or resistance (ohms).
 
 
 
• Local / Distance Switch - Changes the sensitivity of the tuner. When switched to local (LO), the stronger local stations are received with a higher image rejection. When switched to distance (DX), the weaker, distant stations are received but with less image rejection.
 
 
 
• Loudness Control - Intended to boost low frequencies at lower volume levels and should not be used at high volume listening levels.
 
 
 
• Loudspeaker - An electro acoustic transducer which converts electrical audio signals at its input to audible waves at it's output. May also refer to a given driver of a multiple speaker system and not to the whole speaker system as might a speaker.
 
 
 
• Loudspeaker Compliance - The acoustical and mechanical equivalent of capacitance. Determines how easily a speaker cone/ voice coil assembly will move when an electrical signal is applied to it.
 
 
 
• Low Frequency Driver - A loudspeaker specifically designed to reproduce long, low-frequency wave lengths. The driver typically has a large cone, magnet structure, and voice coil. Woofer.
 
 
 
• Low Pass Filter - A network of elements used to attenuate all frequencies above a predetermined frequency. Frequencies below the cutoff point pass without any effect.
 
 
 
• Lows - Term which refers to a set of speaker components used to reproduce frequencies below 500 Hz as in a set of woofers. May also refer to the low frequency drivers of a set of separates. Not treble.

• Magnetic Flux - The magnetic lines of force produced in the area around an electric current or magnet.
 
 
 
• Magnetic Structure - The part of loudspeaker comprising the magnet, pole piece, back plate and top plate.
 
 
 
• Mega (M) - A prefix that means 106 (one million in the US). 1 MHz equals 1,000,000 Hertz.
 
 
 
• Micro (µ) - A prefix that means 1/ 106 (one millionth in the US). 1 µV equals 1/1,000,000 of a volt.
 
 
 
• Midrange Driver - A loudspeaker specifically designed to reproduce the frequencies in the middle of the audible bandwidth. Usually between three and eight inches in diameter. Commonly referred to as the low frequency driver in a set of separates.
 
 
 
• Milli (m) - A prefix that means 1/ 103 (one thousandth). 1 mA equals 1/1,000 of an amp.
 
 
 
• Monaural (mono) - A sound recorded or reproduced in only one channel.
 
 
 
• MOSFET - Metal Oxide Semiconductor Field Effect Transistor. Typically used in high power output amplifiers.
 
 
 
• Mute - Silent, attenuate.

• Nano (n) - A prefix meaning 10-9 or 0.000 000 001
 
 
 
• Noise - 1 Unwanted sound of no specific frequency or amplitude. 2 Random sound of many frequencies not harmonically related (buzzing, hiss, pops, static, whine, etc.).

 
• Occupational Safety and Health Act (OSHA) - The United States governmental agency that establishes and enforces safety standards in the workplace.
 
 
 
• Octave - 1. The interval of eight diatonic degrees between two musical tones. 2.The doubling or halving of frequencies.1000Hz is an octave higher than 500Hz.
 
 
 
• Ohm - The unit of electric resistance and impedance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
 
 
 
• Ohm's Law - Current in a circuit is directly proportional to the voltage, and inversely proportional to resistance.It also includes the relationships of watts to amps, volts and ohms.
 
 
 
• Oversampling - Doubling or quadrupling (or by even a higher factor of 2 squared) the sampling frequency during the digital to analog process to obtain a high frequency for digital filtering.

 
• Parallel Circuit - A circuit configuration in which the same voltage is applied to all components, with current divided among the components according to their respective resistances or impedances. Example: All positive leads of two or more speakers connected together and all negative leads connected together.
 
 
 
• Parametric - A type of equalizer with adjustable parameters such as center frequency and bandwidth (Q) as well as amplitude.
 
 
 
• Peta (P) - A prefix meaning 1015 or 1,000,000,000,000,000
 
 
 
• Phase - The relative position of two sound waves with respect to each other.
 
 
 
• Photo Detector (photo diode) - A semiconductor device which provides variations in current as a function of light intensity.
 
 
 
• Piezo Electric Tweeter - A very efficient, highly directional tweeter which operates without a crossover or magnet. Driver creates sound when a quartz crystal receives electrical energy.
 
 
 
• Pink Noise - Sound with all frequencies perceptible to the human ear reduced to an equal energy level.
 
 
 
• Pink Noise Generator - A device used to generate pink noise that usually includes a calibrated microphone.
 
 
 
• Pit - One of the depressions that represents data in a compact disc. May also be referred to as bumps, this is what the pick up sees.
 
 
 
• Plate Speaker - A speaker that has two drivers mounted side by side on a flat surface.
 
 
 
• Polarity - The electrical quality of having two opposite poles, one positive and one negative. Polarity determines the direction in which a current tends to flow.
 
 
 
• Pole Mount - A common automotive speaker design with the high frequency driver mounted on a center pole. Newer designs mount the high frequency driver in the same location above the lower frequency driver with a bridge. This prevents problems such as dust and dirt from entering at the base of the pole.
 
 
 
• Power Handling Capability - The maximum amount of power that can be safely accommodated without damage in a speaker system. This will vary depending on frequency and length of time the signal is applied.
 
 
 
• Pre-amp Fader - A circuit that allows effective level control of two amplifiers, built in and external without loss of power.
 
 
 
• Pre-amplifier (pre-amp) - The circuit which takes a small signal and amplifies it to be fed into the power amplifier for further amplification. Contains controls for volume, regulating tone, and channel balance.

• Quantization - The assigning of values to discrete samples of a continuous signal in the analog to digital conversion process.

• Radio - A head unit that combines a tuner, a preamplifier, and a power-amplifier.
 
 
 
• Radio Frequency Interference (RFI) - Electromagnetic waves between the frequencies of 10 KHz and 300 GHz that can affect susceptible systems by conduction through sensor (tape head) or power input lines, and by radiation through space.
 
 
 
• RAM - Random Access Memory. A memory device that one can write data to and read data from.
 
 
 
• Relay (SPDT) - (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87).
 
 
 
• Remote Turn On Lead - The lead from the head unit which supplies a signal (12V+) to the "remote turn on" lead of the amplifier turning the amplifier on when the head unit is turned on, and allowing the amplifier to be mounted in a location out of reach of the user. This is NOT the amplifier's main source of power.
 
 
 
• Resistance - The opposition to the flow of AC or DC voltage in an electric current. Measured in ohms.
 
 
 
• Resistor - An electrical device that resist the flow of electrical current. The higher the value of resistance (measured in ohms) the lower the current will be.
 
 
 
• Resonance - Pitch. When you tighten a drum, you raise it's resonance.
 
 
 
• Resonant Frequency - Frequency at which there is a response peak, due to a specific interaction of inductive and capacitive circuitry in an audio devise or system.
 
 
 
• RMS - Root Mean Square.
 
 
 
• ROM - Read Only Memory. A memory device that one can only read data from. The data has been pre-programed.

• Sabine - Unit of measurement for absorption. One sabine is equal to the absorption of 1 square foot of surface which will absorb all incident energy.
 
 
 
• Sampling - Measuring the analog signal at a fixed rate of speed (sampling frequency).
 
 
 
• Sealed Enclosure - A type of speaker enclosure that does not allow the pressure generated by the back wave of the speaker to leave the enclosure.
 
 
 
• Selectivity (alternate channel) - Similar to capture ratio, but deals with signals which are broadcast on frequencies very close to the one selected.
 
 
 
• Sensitivity (loudspeaker sensitivity) - The sound pressure level a speaker produces when fed by a given input power, measured at a specific distance on axis directly in front of the speaker. Typically specified in dB SPL at 1 meter with 1 watt of input signal.
 
 
 
• Separates - A speaker system with more than one type of driver. The most common type of separates system is a set containing two high frequency drivers (tweeters), two lower frequency drivers (mids or woofers), and two crossover networks (filters).
 
 
 
• Separation - The degree to which left and right channels in a stereo signal can be kept apart.
 
 
 
• Series Circuit - A circuit configuration in which a single current path is arranged among all components. Connecting the positive speaker output of an amplifier channel to the positive terminal of speaker # 1 , connecting the negative terminal of # 1 to the positive terminal of speaker # 2, and the negative terminal of # 2 to the negative output of the same amplifier channel is a series connection.
 
 
 
• Shield - A metallic foil or braided wire layer surrounding conductors which is designed to prevent electrostatic or electromagnetic interference from external sources.
 
 
 
• Signal - Any electrical transmittance that conveys data.
 
 
 
• Signal-to-Noise Ratio (S/N) - The ratio of the desired signal level to the level of unwanted noise. Measured in decibels.
Signal-to-Noise Ratio
10.0 dB
20.0 dB
30.0 dB
40.0 dB
50.0 dB
60.0 dB
70.0 dB
80.0 dB Times Signal is Greater than Noise
3.16
10.00
31.62
100.00
316.20
1,000.00
3,162.00
10,000.00
 
 
 
 
• Slope - The rate of boost or attenuation expressed in decibels of change per octave.
 
 
 
• Sound - A wave propagated in air producing an auditory sensation in the ear by the change of pressure at the ear.
 
 
 
• Sound Field - The total acoustical characteristics of a space, such as ambience [number, timing, and relative level of reflections (ratio of direct to reflected sound)].
 
 
 
• Sound Pressure Level (SPL) - An acoustic measurement of sound energy, typically expressed in dB SPL.
 
 
 
• Sound Stage - The area that appears to be occupied by sonic images. as with a real stage, a sound stage should have depth, height, and width.
 
 
 
• Speaker - A transducer which converts electrical energy into acoustical energy (sound).
 
 
 
• Standing Waves - Created when two waves in opposite directions interfere. When a reflected wave reinforces a reflection of the original waveform, the sound waves reinforce themselves, increasing in altitude.
 
 
 
• Stereophonic (stereo) - Consisting of two or more audio channels in an audio system during recording and playback to give a more natural distribution of sound.
 
 
 
• Sub Harmonic - The result of the division of the fundamental frequency by the desired number harmonic. The sub harmonic of 1000 Hz is 500 Hz.
 
 
 
• Subcode - Data, other than music, which is stored on a CD, MD, or other digital format. Used to indicate track number, index number, use of emphasis, and other information.
 
 
 
• Sub-woofer - A loudspeaker made to reproduce the lowest of audio frequencies, approx. 25 Hz to 125 Hz.
 
 
 
• Supertweeter - A high frequency driver designed to reproduce very high frequencies, typically over 10 kHz.

• Tera (T) - A prefix meaning 1012 or 1,000,000,000,000 (one trillion in the US).
 
 
 
• Threshold of Pain (in dB SPL) - The minimum value of sound pressure of a given frequency that will cause pain to a listener 50% of the time. Discomfort begins at 118 dB SPL Actual pain starts around 140 dB SPL within the frequency range between 200 Hz and 10,000 Hz.
 
 
 
• TOC / Table Of Contents - The subcode information which contains track numbers and times.
 
 
 
• Total Harmonic Distortion (THD) - The noise referenced to signal in decibels (dB) as a percentage.
Noise referenced to Signal
-10.0 dB
-20.0 dB
-30.0 dB
-40.0 dB
-50.0 dB
-60.0 dB
-70.0 dB
-80.0 dB  Percent Distortion
31.6%
10.0%
3.16%
1.00%
0.316%
0.100%
0.0316%
0.0100%
 
 
 
 
• Tracking Servo - The control circuit used to keep the pick-up over the desired track.
 
 
 
• Transducer - A device used to convert energy from one form to another. Acoustical to electrical (microphone), electrical to acoustical (speaker), and electrical to mechanical (Aura Bass Shaker) are three examples of transducers.
 
 
 
• Transistor - A three terminal device used for amplification and switching.
 
 
 
• Tuner - A component (or section of one) that receives radio signals and selects one broadcast from many.
 
 
 
• Tweeter - A high frequency driver specifically designed to reproduce only the high frequencies (treble) of the audible spectrum

• Underlap - The crossover point being more than 3 dB below the unattenuated level.

• Voice Coil - Coil of wire wrapped around a tube and attached to the speaker cone or driver diaphragm. Becomes an electromagnet when an audio signal is applied and interacts with a permanent magnet which causes the cone or diaphragm to vibrate.
 
 
 
• Volt - The unit of measure for electrical potential.
 
 
 
• Voltage - he difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit.

• Watt (wattage) - A measurement of real power. The product of voltage and current in a resistive circuit.
 
 
 
• White Noise - Noise in which a constant energy level per unit (1 Hz) is maintained in all frequencies.
 
 
 
• Woofer - A loudspeaker made to reproduce the lower range of the audio spectrum (bass), in a 2-way or more complex speaker system.
 
 
 
• Wow and Flutter - Usually refers to the inconsistencies in tape speed which cause pitch variations and quivering sounds. Wow is slow-speed variations, and flutter is fast-speed variations. Expressed as a percentage, with lower numbers being better.
 
 
 
 
 
• XM Radio - XM Radio broadcasts 100 channels of totally new music, news, sports and children's programming direct to cars and homes via satellite an extensive repeater network, which supplements the satellite signal to ensure seamless transmission. The channels originate from XM's broadcast center, the world's largest all-digital studio complex in Washington, DC, and uplink to two Boeing 702 satellites. These satellites transmit the signal across the entire continental United States. Each satellite provides 18kw of total power making them the two most powerful commercial satellites ever built, providing coast-to-coast coverage.
 
 
 
• Xmax - The maximum linear cone excursion of a driver.

• Yocto (y) - A prefix meaning 10-24 or 0.000 000 000 000 000 000 000 001
 
 
 
• Yotta (Y) - A prefix meaning 1024 or 1,000,000,000,000,000,000,000,000

• Zepto (z) - A prefix meaning 10-21 or 0.000 000 000 000 000 000 001
 
 
 
• Zero Output - The absence of output signal or output power.
 
 
 
• Zetta (Z) - A prefix meaning 1021 or 1,000,000,000,000,000,000,000
 
 
 
• Zobel - A filter used to stabilize speaker impedance at a crossover frequency where impedance has risen to twice the nominal impedance.
 
 
 
• Zone - A specific area of a security system's coverage. A specific trigger input of an alarm.