| ohm | The basic unit of the measurement of resistance. Symbol used is (Omega) |
| Ohm's Law | The law that defines the relationship between current (I), resistance (R) and voltage (V) in an electrical circuit as: Voltage equals Amperage times Resistance (V=IR). |
| on-axis | Directly in front of a speaker; position at a right angle (90-degree angle) to the front of a speaker enclosure on which the speaker drivers are located (the baffle). |
| optical cable | An interconnect cable used to transfer digital data between digital components using bursts of light carried over glass or plastic fibers (see Fiber-Optic Cable). |
| Optical Dual Veri-Focal | Option for normal field of view or wide angle, using the same lens and image sensor. Tigershark cameras use only 60% of the image sensor in normal mode, but 100% in wide mode. Wide mode produces a wide angle view using the same lens, without keystone effect or blooming at the edges of the sensor. Dual optical lens - 2 focus points - advantage is you get full resolution in either mode. |
| OSD | On Screen Display. A device that has OSD allows the installer to use navigational controls and a video display to choose options from an on screen menu. |
| parametric equalizer | An audio equlaizer that uses variable frequency, Q and amplitude control. |
| passive crossover | Crossover that does not require electricity and does not use active circuitry to accomplish its task. |
| passive radiator | Speaker driver that is not powered and is used in conjunction with a woofer generating movement by being vibrated by the back-pressure of the powered woofer. |
| patch bay | A panel of jacks (female receptacles) hard-wired to all inputs, outputs and side-chains of outboard equipment, and all outputs and insert points of the mixing console. Often used in recording studios to enable rapid connection of any combination of equipment by the use of 'patch cords', or 'patch leads'. |
| patch cable | Low level cable used to transfer information in an electronic form between components in an audio/video system (see Interconnect). |
| PCM (Pulse Code Modulation) | PCM (Pulse Code Modulation)Frequently used format for creating digital signals from analog signals and then recreating the analog signals with a digital-to-analog converter (see Pulse Code Modulation). |
| peak limiting | A compressor set up with a high ratio (in excess of 10:1) and used primarily to prevent a signal from exceeding a certain pre-set maximum level. (See also "Limiting") |
| peak output | Maximum output (sound pressure level) in decibels a speaker can produce without distorting. |
| peak power | A measure of amplifier power based on the amplitude rise above ground plane or 0 volts. |
| peak-to-peak power | A measure of amplifier power based on the total amplitude between peak positive value and peak negative value. Generally this value is twice the peak value for a symmetrical waveform. |
| phase | The relationship of an audio signal or sound wave to a specific time reference. |
| Phoenix connector | Phoenix is a brand name for a solderless connector block; or more generically known as a "pluggable terminal block" or a "two piece terminal block". The terminal block is a solderless connector that uses screw terminals to clamp connecting wires. |
| pink noise | Broadband test noise where the amplitude has a linear -3dB per octave attenuation as frequency increases. |
| Pixel (Picture Element) | The smallest piece of data in a video image. The smaller the pixel size in an image, the greater the resolution. Resolution is counted in horizontal and vertical pixels, e.g. 1920x1080. |
| plasma display (PDP) | A display that is made of thousands of tiny tubes filled with ionized gas in a plasma state. |
| plenum rated | Jacketed wire that is fire-retardant, approved for installation in plenum ceilings. |
| polarity | A condition with two states (+ve or -ve) and is usually defined in one of three ways: 1. Acoustical to electrical (microphone): Positive pressure at diaphragm produces positive voltage at pin 2 of XLR or at the tip of a 1/4-inch phone plug. 2. Electrical to acoustic: Positive voltage into the "plus" terminal of a speaker causes the speaker's diaphragm to move forward to produce positive pressure. 3. Electrical to electrical: Positive voltage into pin 2 of an XLR jack produces positive voltage at the output (pin 2 of an XLR plug, the tip of a 1/4-inch phone jack, or the red (plus) connector of a binding post (banana terminal). |
| port (speaker enclosure) | Tube of a specified length and diameter (length and diameter dependent on specific application) with one end open to the outside of a speaker enclosure through a round hole and the other open to the inside of the speaker enclosure. |
| post-processing | The reference of processing after it leaves the previous stage. |
| potentiometer (pot) | A variable resistor (rotary or linear) used to control volume, tone, or other functions of an electronic device. |
| power | In electricity, power (P) is the product of the voltage (V) and the current (I). i.e. P=VI. The unit of power is the Watt. |
| power amplifier | An amplifier without tone controls, and with a higher power output than a line amplifier or pre-amp. Commonly used to drive loudspeakers. |
| power rating | Maximum amount of power in watts an amplifier can put out or maximum amount of power in watts a speaker can be driven with. |
| power supply | Component of all electronic devices used to transform the electrical power supplied through a wall outlet into power the electric component can use. |
| powered subwoofer | A speaker designed to reproduce a range of very low frequencies only. A stand-alone component powered by a built in amplifier. |
| pre-amplifier or pre-amp | An electronic device used to match an input signal (such as that from a microphone or guitar pickup) to the input of a power amplifier. Often built in to mixing console channels as an initial stage, and generally has tone controls (EQ) to modify the signal. |
| pre-processing | The reference of processing before it enters the next stage. |
| progressive scanning | As in 1080p or 2160p. Picture display process that shows 1080, or 2160 vertical lines scanned in succession in a vertical frame and then repeated 60 times in a second. This displays a smooth picture compared to the interlaced process, e.g. 1080i, or 2160@30fps. |
| propagation (sound) | Under normal conditions an audio wavefront moves through air at 1130 feet per second. |
| PSB | Product Select Button. Styles include stainless steel or plastic in different sizes and LED colors. These are used to select products in AccessEZ or 1700 Series demonstration systems, or to adjust volume. |
| psycho acoustic | The science of how audio is perceived. |
| pulse code modulation | Common form of transferring analog information into digital signals by representing analog waveforms with a stream of digital bits forming words that relate the amplitude of a signal at a certain point (the sample). |
| Q or Q factor | Quality or Quality Factor - Referring to the bandwidth of one band of a parametric equaliser, Q is calculated by dividing the centre frequency in Hz by the width of the boost or cut zone +3dB or -3dB above or below 0dB. For example, a gentle boost centred at 1000Hz which extends from 750Hz to 1250Hz measured 3dB above flat has a Q of 1000/500 = 2. By comparison, a deep notch centred at 1000Hz which extends from 995Hz to 1005Hz measured -3dB above flat has a Q of 1000/10 = 100. |
| rack-mountable | Describes outboard equipment designed to be mounted in a standard 19" EIA 'Effects Rack'. |
| ratio | One of the parameters which can be varied on dynamic range processors such as compressors and expanders. It represents the compression or expansion ratio between input and output levels. A compressor with a 2:1 ratio would reduce the output gain to half of the input value above the threshold. An expander with a 1:80 ratio would reduce the output gain to 1/80th of the input value below the threshold. |
| RCA connector | (Also reffered to as a "Phono-Pin-Plug") Type of standard, low-level signal interconnect termination or connector featuring a single, cylindrical metal rod and an outer, round metal belt. |
| reflex (bass reflex) | Type of speaker enclosure which uses a port to allow air to travel from the inside of the box to the outside of the box taking full advantage of a speaker driver's output and increasing sound pressure (sound output or volume) by 2 to 3 dB compared to a similar speaker with a sealed enclosure (see "Bass Reflex"). |
| resistance | A block to the flow of something; creating a difficulty of flow or hampering flow particularly the flow of an audio signal as a current in terms of audio/video (see "Impedance"). |
| resolution | The density of lines and dots per line, which make up a visual image. The number of pixels measures resolution. The more lines and dots means a sharper and more detailed picture. Regular TV has about 200,000 pixels, While, HDTV (1080 vertical pixels and 1920 horizontal pixels) has more then 2 million pixels creating the image. |
| resonant frequency | Frequency at which a speaker vibrates in unison with the audio signal creating vibrations in the enclosure and driver with very little input. |
| reverberation | Reflection of sound waves against room boundaries and objects within the room persisting after the original sound has ceased. |
| RF (Radio Frequency) | RF waves can be transmitted and received through walls and other physical barriers and differs from IR (infrared) technology, which requires a clear line-of-sight between transmitter and receiver. |
| RF (Radio Frequency) | Wide frequency range of electromagnetic signals from around 10 kHz (10,000 Hz) to 300 GHz (300,000,000,000 Hz. |
| RF modulation | Method of placing an audio signal with a relatively low 20 to 20,000 Hz frequency on top of a much higher frequency radio frequency (in the area of 100,000,000 Hz) by varying the frequency of the radio signal according to the audio signal so that the audio signal can be sent over long distances and distributed through broadcast antennas (see FM). |
| RFI | Radio Frequency Interference - An undesirable form of audio rectification that occurs in an audio circuit when radio frequency energy is present demodulated and mixed into the audio signal. |
| RFI (Radio Frequency Interference) | Interference caused by CB radios, radio stations, microwave ovens, power lines, cellular phones, etc. which can cause noise and distortion affecting sound and audio quality for audio-video components. |
| RG/U | A standard used for referencing coaxial cables, such as RG6/U or RG59/U, RG is a military standard for Radio Guide. |
| RMS | Root Mean Square: A method of calculating the average power generated by a sinusoidal waveform. Used for comparing amplifier power, it is a more realistic measure than 'peak' power or 'peak-to-peak' power. |
| roll-off | Decrease in signal or sound pressure in decibels as a speaker or speaker driver attempts to reproduce frequencies outside of its primary frequency range (a midrange driver may roll-off at 500 Hz and its output decreases from that point); attenuation of frequencies outside a range specified in a crossover network (see Slope). |
| room EQ or room tuning | The process of compensating for acoustic deficiencies in both venues and PA systems using graphic equalisers in FOH and foldback signal paths. |
| room interaction | Description of how the room or space affects the quality of sound produced through an audio system or live audio performance. |
| RS-232 | RS232, Recommended Standard 232 is a standard introduced in 1960 for serial communication transmission of data. |
| 'U' | Stands for 'Rack Unit': standard front panel height (1.75" or 4.44cm) used for pro-audio equipment to enable mounting in an equipment cabinet - see Effects Rack. |
| S/N ratio (Signal-to-Noise ratio) | Maximum output of an electronic device or recording medium compared to its noise floor or level of background noise. |
| satellite speaker | A small- to medium-size speaker usually 12 to 24 inches in height designed to be placed on stands or other objects and operated with a subwoofer (see Bookshelf Speaker). |
| SDN | Software D/N (Day Night) is a technology to make details in a dark scene more visible by removing the chroma (color) signal, resulting in a black and white image that has enhanced contrast. |
| sense up | Image processing technology which allows digital slow shutter speeds to allow more light onto the sensor for each video frame, resulting in better images in low light conditions. Also called “sens-up”,” sensup”, “senseup”, “DSS”, and “digital slow shutter”. |
| sensitivity | Measure of the sound pressure level generated at a distance of one meter from a speaker when the speaker is fed a 2.83 volt signal (1 watt at 8 ohms); efficiency of a speaker creating a certain sound pressure level from a given input with high figures representing a more efficient speaker. |
| serial | Serial is a communication technique used in telecommunications wherein data transfer occurs by transmitting data one bit at a time in a sequential order over a computer bus or RS232 (Rx/Tx channels) communications bus. |
| shielded wire | One or more insulated conductors enclosed by a common conductive layer. Can be made of braided copper strands, or conducting polymer. |
| shielding (cable) | A wire mesh surrounding the conductor(s) inside a cable to prevent outside interference from getting in and to prevent the signal contained in the cable from escaping to other equipment. Some cable types employ "Double Shielding" to further reduce the crossover of signals in or out of the cable. |
| shielding (circuit or chassis) | A metal wall or case designed to keep outside signal(s) from entering or internal signal(s) from escaping a circuit that generates propagating signals. |
| signal processors | Electronic devices which alter sound either to achieve a particular effect or to solve a problem with that sound (e.g. delays, compressors, reverbs, noise gates, equalizers). |
| Signal to Noise ratio | A measure that describes how "clean" a signal is. Measures the strength of an audio or video signal versus the noise and interference. This measure is in dB. |
| sine wave | Type of pure waveform having an equal distance from its peak to the zero or center line and from its trough to the center line and in which the positive hump and negative hump of the wave are exactly equal in length, shape and height but flipped in a mirror image about the center line. |
| slope | How quickly a crossover or filter attenuates signals (decreases their power) outside its passband (those frequencies intended to pass through without attenuation); expressed in decibels per octave. |
| sound wave | Continuous audio frequency signal taking the form of a wavy line similar to waves on the water with frequency determining the length of the waves and amplitude or volume determining the height of the waves. |
| soundstage | The perceived width, depth and height of recorded sound played back over an audio system; the setting similar to a theater stage from which sounds seem to emanate when reproduced through an audio system (see Imaging). |
| speaker configuration | Associated with cinema or home theater; a 5.1, 7.1, 9.1 surround sound speaker configuration creates a complete audio environment. |
| speakers | Devices that convert electrical signals into variations in sound pressure. |
| Speakon connector | A trademarked name for an electrical connector, originally manufactured by Neutrik, mostly used in professional audio systems for connecting loudspeakers to amplifiers. |
| spectrum | A band or range of frequencies; the audible spectrum runs from 20 Hz to 20,000 Hz (20 kHz). |
| spectrum analyzer | Electronic device that measures a particular spectrum or frequency band and displays information about that particular spectrum or band. |
| SPL meter (Sound Pressure Level) | SPL Meter (Sound Pressure Level)Device that measures the sound pressure level in a given location; commonly used in audio to properly set surround sound systems to the Dolby reference level and adjust other parameters of a sound system (see Sound Pressure Level). |
| SRS TruSurround | SRS TruSurround is a multichannel format processing technology that takes a 5.1 audio signal and creates an immersive surround sound experience with deep bass and crystal clear dialog all through the existing built-in TV speakers. |
| standby mode | Low power mode for electronic devices such as computers, televisions, and remote controlled devices. Standby mode saves significant electrical consumption compared to leaving a device fully on and idle, but preserves programming codes, and avoids a full device reboot before each use. |
| standing wave | Low frequency anomaly or distortion created when a certain frequency is reproduced whose size has some special relation to the room or object it is produced in (wavelength the same size as the room dimensions) resulting in the room or object resonating with the sound and increasing the strength of the sound (the sound wave does not diminish and may instead increase as it interacts with its surroundings). |
| stereo | Two channels of audio information (usually oriented Left and Right) recorded and played back in such a way as to recreate a sound stage giving depth and breadth to audio reproduction. |
| streaming | A technique for transferring data so that it can be processed as a steady and continuous stream. Streaming technologies are often used on the Internet because most users do not have fast enough access to download large multimedia files quickly. Streaming allows the client browser or plug-in to start displaying the data (e.g. video) before the entire file has been transmitted. |
| subwoofer | Special form of speaker used to reproduce only the lower portion of the audible frequency spectrum usually from 80 Hz down to or below 20 Hz. |
| surge protection | Protection against lightning strikes and other similar sudden increases in power, which may damage electrical equipment. |
| surround channel | Specific path of audio information, the channel, provided in a surround sound audio system to drive speakers situated on the sides or rear of a room primarily providing ambience and atmosphere. |
| surround channel speaker | Speaker used to reproduce surround channel information primarily to create ambience and sonic realism. |
| surround sound | A multichannel audio system which provides a minimum of 6 channels of audio: Left, Center, Right, Surround Left, Surround Right, and LFE (Low Frequency Effect - AKA Subwoofer) |
| surround speakers | Speakers for the distribution of sound resulting from digital decoding. May be 5.1 channels, which is front speakers (right and left), rear speakers (right and left), center channel speaker, and a powered subwoofer. May be 6.2, which is front speakers (right and left), front center channel speaker, rear speakers (right and left), rear center channel speaker, and two powered subwoofers. Other schemes such as Dolby Atmos also include ceiling speakers. |
| sweep test | An electric quality test procedure performed by network analyzer test equipment measuring coaxial or network cables at various frequencies between 1 MHz and 2.6 GHz. Measurements include attenuation (electrical signal degradation), reflection (return loss), and noise (cross talk). |
| sweet spot | A term referring to the optimum listening position in a room where the listener is correctly positioned relative to the speakers where phasing (reflection time) of the audio signal and optimum frequency response is achieved. Usually located in the middle of the room. |
| system integration | Providing easy control over multiple subsystems in homes or commercial buildings via a single control system. Home automation systems provide convenient control of such subsystems as lighting, HVAC, locks, media systems, blinds, security, and outdoor systems. |
