Audio - Home Theater FAQ's and Information

Audio  - Home Theater FAQ's and Information

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Audio Glossary and Terms N Thru S



Nano - A prefix meaning one-billionth. 

Nano-Webers Per Meter - The standard unit in measuring the amount of magnetic energy.  Near Field - The area up to one foot from the sound source.  Negative Feedback - A portion of the output signal that is feed to the input (of an amplifier), out of phase. Something we just don't ever get here at (Brass & Granite Audio). Neodymium - A very strong rare earth magnet used in speaker motors magnets that allows high sensitivity performance from very small drivers. Noise Filter - A filter used which passes only signals with the intended audio frequencies thus eliminating noise signals at other frequencies. 

Noise Floor - The level of the noise, in dB, below the signal. 

Noise Gate - A gate used to turn off an audio channel when noise but not signal is present. 

Noise Reduction - Any device to remove noise in a device or system. 

Non-Linear - The condition of obtaining a change at the output of the device which is not proportional to the change occurring at the input, causing distortion. 

Normals - Switches on the patch jacks that connect certain jacks together until a patch cord is inserted.  

Normalizing Jacks - Switches on the patch jacks that connect certain jacks together until a patch cord is inserted.  

Notch - A narrow band of audio frequencies. 

Notch Filter - A device that rejects signals that have frequencies within a narrow band of audio frequencies and passes all other signals. 

Null - A point in any electronic system where two out-of-phase signals cancel each other  In speaker acoustics, a null is a point in space where a speakers multiple drivers outputs overlap at crossover frequencies,  but are different enough in phase to decrease the overall sound level.  At the center of nulls, signals interfere strongly enough to entirely cancel, producing a sound level of 0 db. The opposite effect occurs in a lobe (see above).

Nyquest Frequency - The highest frequency that can be recorded and reproduced properly by a particular sampling rate (a frequency that is one-half the sampling rate). 


Ohm's Law - the scientific law, in electrical matters, that says that the power in a closed electric or electronic system is a constant relationship between voltage, amperage and resistance such that V (Voltage)  = I (Amperage) multiplied by R (Resistance).  Given any two of these elements, the third element can be derived by simple multiplication or division.  For example, if a circuit has 28 V of voltage running through it, and 8 ohms of resistance opposing the flow, we can calculate the current for that circuit:   28=I multiplied by 8; I=28/8; 28 divided by 8 =3.5 Amperes.  So for a circuit carrying 28 volts and offering 8 ohms of resistance, 3.5 amps of current will flow.  We can use this same law to calculate voltage knowing only amperage and resistance, or resistance knowing only voltage and amperage.

Omni- - A prefix meaning All. 

Omni-Directional -  In speakers, sending out evenly in all directions. 

Open - Short for the term Open Circuit. 

Open Circuit - 1) Having a break in a conductor or, for another reason, not having a complete path for electrons to flow. 2) Said of an amplifier, having nothing feeding the input. 

Out Of Phase - 1) Being similar to another signal in amplitude, frequency and wave shape but being offset in time by part of a cycle. 2) 180 degrees out of phase or having opposite polarity.

Output - 1) The jack or physical location of where a device sends out a signal. 2) The signal put out by a device.  

Output Impedance - The opposition to current flow by the output circuits of an amplifier (or other device). 

Output Level - The signal level at the output of a device.


Panpot (Pan Pot) - An electrical device that distributes one audio signal to two (or more) channels or speakers. 

Parallel - 1) A circuit interconnection in that the source feeds several branch circuit components and interruption of current flow in one component does not stop current flow in another. 2) A method of sending data where each digit of a digital word is sent at the same time over separate wires/connections.

Parallel Jacks - Several jacks that are wired so that each connection is wired to the corresponding connection of other jacks. 

Parallel Port - A jack that sends out or receives digital data where several bits are being sent/received at the same time though different pins. 

Parameter - Each adjustment that is possible to change in a device. 

Parametric EQ - An equalizer in which all of the parameters of equalization can be adjusted to any amount including: a) center frequency; b) the amount of boost or cut in gain; and c) the bandwidth. 

Pass Band - The frequency range of signals that will be passed, not reduced, by a filter. 

Passive Device - A piece of signal processing gear or other device that does not use an amplifier as part of its design.  

Patch - 1) To route or reroute the signal in an audio system (such as a console) by using short cables with plugs inserted into jacks. 2)The routing or rerouting of the signal accomplished by #1.  

Patch Bay - A Series of jacks with connections for most of the inputs and outputs of the console, console sections, tape machines and other pieces of equipment. 

Patch Cord - A cable with two plugs on it to interconnect two patch jacks in the patch bay. 

Patch Field - A series of jacks which has connections for most of the inputs and outputs of the console, console sections, tape machines and other pieces of equipment. 

Patch Panel - A series of jacks which has connections for most of the inputs and outputs of the console, console sections, tape machines and other pieces of equipment. 

Patch Point - One jack in a patch bay. 

Path - Short for Signal Path, the way in which current does or may travel in a circuit or through a device. 

Peak - 1) The highest point in the audio waveform. 2) Short for Peak Detecting (responding to the peak) or Peak Indicating (showing the peak). 3) Having a frequency response that would draw something similar to a mountain peak on a frequency response graph. 

Peak Detecting - Recognizing and responding to peak values of a waveform rather than average values. 

Peak Indicating Meter - A meter which reads the absolute peak level of the waveform. 

Peak Level - A term with the same meaning as Peak Value (the maximum positive or negative instantaneous value of a waveform). 

Peak Responding - Recognizing and responding to (or indicating) the peak value rather than the average or effective value. 

Peak Response - 1) A term with the same meaning as Peak 2) Raising or lowering of the amplitude of signals at the center frequency more than signals at any other frequency. 

Peak Value - The maximum positive or negative instantaneous value of a waveform. 

Peaking Filter - An EQ circuit which has a peak response (raising or lowering of the amplitude of signals at the center frequency more than signals at any other frequency). 

Peak-to-Peak Value - The difference in amplitude between positive and negative peaks. Equal to twice the peak value for a sine wave. 

Phase - A measurement (expressed in degrees) of the time difference between two similar waveforms. 

Phase Addition - The energy of one waveform increasing the energy of another waveform because the two waveforms have similar phase relationships. 

Phase Cancellation - The energy of one waveform decreasing the energy of another waveform because of phase relationships at or close to 180 degrees. 

Phase Distortion - A change in the sound because of a phase shift in the signal. 

Phase Shift - A delay introduced into an audio signal measured in degrees delayed.  

Phon – 1) A unit of equal loudness for all audio frequencies. 2) The phon is numerically equal to dBspl at 1000 Hz but varies at other frequencies according to ear sensitivity to frequency. 

Pin Plug – 1) A term with the same meaning as RCA Plug. 2) The common audio connector found on most stereo systems with a center pin as one connection and an outer shell as the second connection.

Plug - A connector, usually on a cable, that mates with a jack.

Polypropylene - a versatile form of polymer used for speaker cones because of its low mass and high damping.

Potentiometer - A device that outputs pan of the input voltage according to the position of the control's knob. 

Power- 1) The measurement of the ability of an electrical current to produce light, produce heat or do other work. 2) A similar measurement of another energy form to do work. 3) The name of the switch which turns on a device. 

Power Amplifier - A device that takes a line level signal and amplifies it to be able to drive a speaker. 

Power Supply - An electrical circuit which supplies voltage and current for devices to operate. 

Pre-Amp - A low-noise amplifier designed to take a low-level signal and bring it up to normal line level. 

Pre/Post Switch - A switch on the input module, which determines whether the echo send control comes before or after the main channel fader. 

Pre Emphasis - A boosting of high frequencies during the recording process to keep the signal above the noise at high frequencies.  

Pre Fader - A placement of a send control (or other control) before the main channel fader. 

Pre Fader Listen - A solo circuit that allows a channel signal to be heard (and often metered) before the channel fader. 

Presence Frequencies - The range of audio frequencies between 4 kHz and 6 kHz that often, when boosted, increases the sense of presence, especially on voices. 

Preset - 1) A program of a sound done at the factory by the manufacturer. 2) A set of factory set parameters to give one effect on a signal processing device. 

Protocol - A system of digital data where the positioning of the data, and what each bit in the data stream signifies, is according to a standardized format so all devices can properly interpret the data. 

Proximity Effect - In directional microphones, the boost in the microphone's output for bass frequencies as the mic is moved closer to the sound source. 

Psychoacoustics - The study of how things sound to individuals because of mental or emotional factors.  

Puck - Any circular piece of metal, fiber, rubber, etc., which drives something from a rotating power source. 

Pulse - A rise and then fall in amplitude, similar to a square wave but staying up for less time than staying down. 


Q - The sharpness of the peak response in an equalization circuit.

Quad (Quadraphonic) - A system of four channel sound where the channels are designated as left front, left back, right front, and right back. 

Quality Factor - Quality Factor, (the ratio of reactance to resistance in a coil) which affects Q. 

Quantize - The conversion of the values of an analog wave or random occurrence into steps. 

Quantization - A quantizing (see above). 


Rack Mount - To mount in an equipment rack. 

Rack Space - A standardized size of the front mounting plate in outboard gear equal to approximately 1 3/4" tall by 19" wide.

Radio Frequencies - Frequencies higher than 20,000 Hz (usually above 100 kHz). 

Ramp Wave - A waveform that is similar to a sawtooth waveform but different in that it starts at zero level and gradually rises to its peak level and then instantly drops back to zero level to form one cycle. 

Rarefaction - The air particles being spread apart in the formation of a sound pressure wave.  

Rated Load Impedance - The input impedance (opposition to current flow by an input of a device) that a piece of equipment is designed to feed. 

RCA Plug (jack) - The common audio connector found on most stereo systems.  

Reactance - Opposition to the flow of electrical current which changes with the frequency of the current. 

Reference Level - 1) A standard value used to describe how much level is present in dB above or below this reference. 2) A term with the same meaning as the term Operating Level (the maximum average level that should not be exceeded in normal operation).  

Reference Tones - A term with the same meaning as the term Test Tones (a recording of several single-frequency tones at the beginning of a tape reel at the magnetic reference level that will be used to record the program).  

Regulated Power Supply - A device to supply power to electronic equipment whose output voltage will not fluctuate when more equipment is turned on, or if there is a change in voltage of the power line. 

Relay - An electric switch, when a control voltage is applied to the device, two terminals are connected (or disconnected). 

Relay Rack - An older term for the term Equipment Rack, a cabinet with rails (or free standing rails) that have holes to accept screws at standard spaces and used to house outboard gear.  

Resistance (Ohms, or R) - the opposition that a material offers to the flow of electricity in a circuit.  As every material (including wire and connectors) offers some level of resistance, using components of differing resistance can direct or divert voltage and amperage.  When occurring in a direct current circuit, this opposition to current flow is referred to as resistance; in an alternating current circuit, as impedance.  Resistance can be compared to an upward angle in a pipe carrying water.

Resistor - A device which opposes the flow of electrical current and does so evenly at all frequencies. 

Resonance - The prolonging of the sound at a certain frequency and the tendency of something to vibrate at a particular frequency after the source of energy is removed. 

Resonant - 1) Tending to pass signals of a certain frequency or narrow range of frequencies more than signals of other frequencies. 2) Physical properties that tend to reinforce the energy at certain frequencies of vibration. 

Resonant Frequency - The frequency at which a physical item tends to vibrate after the source of energy (causing the vibration) is removed. 

Resonate - 1) To vibrate at the resonant frequency. 2) To linger on, as in reverberation, said of sound in a room or used to describe a room/area that has reverberation with a long reverb time.  

RF Interference - The induction (generation of current by magnetic lines of force cutting a conductor) of RF signals (usually broadcast by television and radio stations) into audio lines causing noise, buzz and static.

Ringing - An undesirable resonance at the cut off frequency of a filter that has a high rate of cut-off. 

Rise Time - How fast an audio waveform makes a sudden increase to a higher level.

Roll-Off - The reduction of signal level as the frequency of the signal moves away from the cut-off frequency, especially when the cut-off rate is mild. 

Room Sound - The ambience of a room including the reverberation and background noise. 

Room Tone - The background noise in a room without people speaking or music playing. 

Root Mean Square - The effective average value of an AC waveform, abbreviated: RMS.

Round Sound - A pleasingly balanced sound (having a pleasing mixture of high frequency to low-frequency content). 

RMS - The effective average value of an AC waveform.  

RMS detecting - A control circuit that recognizes and responds to the effective average, the RMS level (see preceding entry) rather than to the peak level.  

Rumble - A low-frequency noise, especially that caused by earth/floor vibration or by uneven surfaces in the drive mechanism of a recorder or playback unit. 


Sample Rate - In digital recording, the number of times per second that samples are taken.

Sampling Frequency - Same as Sample Rate (the number samples taken per second). 

Satellite - when used with a larger subwoofer, smaller front left and right main speakers (either physically smaller or set to "small" in multi channel speaker setups) are sometimes referred to as "satellites."   In common use, the term can apply to physically or electronically small rear or surround speakers as well.

Sawtooth Waveform - A waveform that jumps from a zero value to a peak value and then gradually diminishes to a zero value for each cycle. 

Schematic Diagram (Schematic) - A diagram that shows the signal paths and electronic components of a device. 

Sensitivity - The ratio of output power to input power in a speaker system, defined as either as power sensitivity or voltage sensitivity.  Power sensitivity is determined by inputting one watt into a speaker and measuring what comes out; the ratio is the power sensitivity rating.  The current/voltage relationship depends on the speakers impedance. 

Most manufacturers quote voltage sensitivity for their speaker products. Voltage sensitivity is the ratio of output power to input power when 2.83V is applied across the speaker terminals.  The resulting sound output is measured  at a distance of one meter and the result expressed in decibels (dB). 

Shield - 1) The outer conductive wrapping around an inner wire or inner wires in a cable. 2)To protect the inner wire or inner wires in a cable from pick up of energy given off by such things as florescent lights.  

Shielded Cable - Cable that has a shield around an inner conductor or inner conductors.  

Shortest Digital Path - The routing of the digital audio signal so that there is a minimum amount of D/A conversion, A/D conversion or Sample Rate conversion. 

Signal - 1) In audio, an alternating current (or voltage) matching the waveform of, or being originally obtained from a sound pressure wave. 2) Also in audio, an alternating current (or voltage) between 20 Hz and 20,000 Hz. 3) A digital audio bit stream.  

Signal Flow - The path that a signal moves through an audio system such as a console. 

Signal to Noise Ratio (SNR or S/N) - The ratio of maximum signal level to the residual noise level, or noise floor, of an electronic component.  Usually measured on a logarithmic scale in dB, this also indicates a components dynamic range. 

In room acoustics, SNR is measured by first establishing the rooms noise floor (background noise from vents, mechanical equipment and leakage from outside sources) and then comparing that  to the maximum acoustic output of the rooms speaker system. The ratio will be the signal to noise ratio of the room.

Signal to Quantization Noise Ratio (SQNR) - A measure of the quality at which analog signals are converted (ie, quantized) to digital signals, expressed in decibels.  The ratio is approximately equal to 6 times the number of bits accommodated by the analog to digital converter, or ADC.   For example, the maximum achievable SQNR for quantizing at 16-bit detail is around 96 dB, which is known as CD quality.  SACD, at the equivalent 20 bits, achieves an SQNR of 120 dB, and DVD-A, at 24 bits, of 144 dB.

Sine Wave - The waveform that would be obtained from a vibrating source that was vibrating at just one frequency (making a pure tone).

Solder - A soft mixture of metals used to make a bond between two metal surfaces by melting. In audio work the mixture is usually tin and lead which is used in permanently connecting wires to terminals.  

Soldering - The action of making connections with solder (a soft mixture of metals used to make a bond between two metal surfaces by melting).  

Solid State - In electronics, using transistors and semiconductor devices rather than tubes. 

Sound Absorption - Same as Acoustical Absorption (the action or quality of a surface or substance to absorb sound rather than reflect it). 

Sound Blanket - A thick blanket that can be put on floors or hung to help prevent sound reflections. 

Sound Level - A shortening of the term Sound Pressure Level (a measure of the sound pressure created by a sound). 

Sound Level Meter - A device that measures the sound pressure levels. 

Sound Patch - Full name of the term Patch

Sound Pressure Level (SPL) - The ratio of the pressure of a sound wave to standard, normative air pressure level, expressed in decibels, or dB. Everyday sound pressure level differences can be extreme: a whisper is 20 dB, normal speech 70 dB, a passing subway train 100 dB, large jet } {plane, 120 dB. Sound pressure levels are measured upward from the point just below audibility, that is, right above the standard noise level created by random thermal currents in a room.  Humans perceive a change in SPL of 10 times as a doubling of loudness; that is, a change in SPL of 10 dB is perceived as twice as loud, not 10 times as loud.

Sound Pressure Wave - Alternate compressions (compacting together) and rarefactions (spreading apart) of air particles moving away from something that is vibrating between 20 and 20,000 times a second or a similar occurrence in another substance (such as water).  

Sound Quality - A microphone characteristic of how well the diaphragm movement matches the pressure changes of a sound pressure wave reaching it, especially sudden changes.  

Sound Source - Something that vibrates between 20 times a second and 20,000 times a second and therefore makes a sound pressure wave. 

Sound Wave - Short for Sound Pressure Wave (a wave of pressure changes moving away from something that is vibrating between 20 times a second and 20,000 times a second).  

Source - Input mode on a tape machine where the meters and the output of the machine's electronics will be the signal arriving at the input connector. 

Speaker - A device that changes electrical signals to sound which can be heard; a transducer changing the electrical audio signal into a sound pressure wave. 

Speed of Sound - The wave velocity (the time it takes for one point of the waveform to travel a certain distance) of a sound pressure wave, 1130 feet per second at 70 degrees Fahrenheit.  

Spin Control - A British term for Feedback Control (a control that determines the amount of delayed signal sent back to the input of a delay line, used in repeat echo effects).  

SPL - An abbreviation of Sound Pressure Level, referring to a pressure of .0002 microbar, considered to be the Threshold of Hearing (lowest level where people begin hearing sound). 

Stereo - A recording or reproduction of at least two channels where positioning of instrument sounds left to right can be perceived.  

Stereo Image - The perception of the different sound sources being far left, far right or any place in between.  

Stylus - The needle part of the phonograph cartridge that is in contact with the grooves of the disc. 

Subcode - Control information bits that are recorded along with digital audio and can be used for control of the playback deck (functions as program number, start ID's, skip ID's etc.). 

Subframe - A unit smaller than one frame in SMPTE time code. 

Subwoofer - A speaker driver designed to operate over the low bass portion of the audio range, generally considered to be below 50 Hz.  Also, a system consisting of such a woofer and its enclosure which are physically separate from the main loudspeakers.  Subwoofers designs are usually either ported (ie, have open bass vents), which offer higher output but less accuracy, or sealed, which offer lower output but more accurate musical reproduction.

Two-way, three-way, four-way speakers -  different types of speaker designs intended for varying purposes.

Two-way speaker - a speaker system with two individual drivers covering the audio frequency spectrum in two bands.  Two-way systems represent a good compromise between size, cost, complexity and bass extension.  The function as a general purpose design, can serve well in wide variety of roles, but for the most part lack the ability to produce deep bass at higher output levels.

Three way speaker - a speaker system with three individual drivers to cover the audio frequency spectrum.  Three-way systems generally have more bass extension and more dynamic range; ie, will play louder, than two-way systems, but are more complex to design and build and are usually larger and more expensive.

Four-way speaker - a speaker system with four individual drivers to cover the audio frequency spectrum.  Larger and more complex than the others above, they usually offer yet greater bass extension and dynamic range.  Four-way systems are generally the most complex systems built using conventional passive crossovers. Restricting the bandwidth of each driver  by using four drivers as opposed to two or three to cover the entire audible frequency spectrum, gives the designer the opportunity to extract the maximum performance from each driver.

Sum - A signal that is the mix of the two stereo channels at equal level and in phase.

Sum and Difference Signals - When the two stereo channels are mixed at equal levels and in phase, the sum signal is created. 

Surround Sound - A technique of recording and playback of sound used in film where the sound has a front to back quality as well as side to side perspective. 



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