| earth ground | An electrical connection to the earth, which represents 0 volts or 'ground potential' by way of a metal or conductive rod. |
| echo | The combined effect of a sound and a delayed version of that same sound. A 'Slap-Back Echo' is the original sound plus a single repeat; "Multiple Echo" is the original sound plus several repeats with the same delay spacing. |
| EDID | Extended Display Identification Data (EDID) is a metadata format for display devices to describe their capabilities to a video source (e.g. graphics card or set-top box). The data format is defined by a standard published by the Video Electronics Standards Association (VESA). |
| enclosure | The cabinet or structure of a speaker into which the various speaker elements (the drivers, the crossover, the binding posts, etc.) are placed and attached. |
| EQ / equalization | The increase or decrease in level of certain portions of the audio frequency spectrum imposed by a device or acoustic environment. Changing the frequency response of a given audio signal by adjusting the amplitude of the signal usually in an effort to achieve a flatter frequency response (although often misused to alter the audio signal to a more "pleasing" form which is a distortion of the intended signal - for instance, artificially adding bass for a more visceral impact). |
| Ethernet | Ethernet is the most widely-installed local area network (LAN) technology. |
| excursion | The distance a speaker driver travels to reproduce an audio frequency. |
| expander | A type of dynamic range processor which reduces the gain of audio signals which are under an adjustable 'threshold' level, therefore increasing the dynamic range. Generally allows the operator control over threshold, ratio, attack, release and 'hold' times. Both analogue and digital types are available. |
| feedback | Sound produced by an instrument or microphone picking up and amplifying its own signal from a nearby loudspeaker. Also known as 'howlaround'. |
| fiber-optic cable | A cable that uses light beams to transmit information rather than electrical signals traveling over metal wires. |
| filter | A device that removes unwanted frequencies or noise from a signal. |
| flat / flatness | Audio frequency amplitude is considered to be "Flat" if a faithful reproduction of the original input source is achieved at the output. If the audio amplitude in a given frequency range of an audio signal is the same as the source audio, then it is said to be "Flat". |
| Fletcher Munson curve | Tones of the same SPL but with different frequencies are in general judged as having different loudness. SPL is thus not a good measure of loudness, if we inter compare tones of different frequency. Experiments have been performed to establish curves of equal loudness, taking the SPL at 1 KHz as a reference quantity. This relative curve of perceived loudness is referred to as the "Fletcher Munson Curve" named after the audio experimenters who developed it. |
| floorstanding speaker | A specific type of speaker enclosure that stands directly on the floor without needing to sit on something in order to raise its speaker drivers to an acceptable height in line with the listener. |
| FLV | Flash Video is a container file format used to deliver digital video content (e.g., TV shows, movies, etc.) over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There are two different video file formats known as Flash Video: FLV and F4V. |
| FM (Frequency Modulation) | Method of adding an audio signal to a carrier radio frequency (modulating the signal) so that the audio signal can be transmitted from place to place and later decoded from the radio frequency for reproduction. |
| fps (frames per second) | In video for television, a frame is comprised of two fields of information originally each at a rate of 1/60th of a second. Hence a frame rate (or speed) of 30 fps. Motion pictures have a lower frame rate of 24 fps so a conversion is necessary for films to play on televisions at 30 fps. There are also higher frame rates in UHDTVs that can handle 60 fps. |
| frequency | Number of times per second that a signal fluctuates. The standard unit for frequency is hertz (Hz). |
| frequency | The number of complete cycles that a sound wave goes through in each second. Unit used is Hertz, abbreviated to Hz, although some countries still use the older term 'cycles per second' (cps). Humans perceive frequency subjectively as pitch (eg: 440Hz = A). |
| frequency response | In audio, the range from low-to-high of frequencies that an audio device (e.g. loudspeakers) can reproduce typically expressed in Hertz (Hz). Since most devices cannot reproduce all frequencies in the spectrum at the same volume level (amplitude) the response range is usually accompanied by a variant in decibels (dB) to show how "smooth" or linear the response range is like 20 - 20kHz +/- 3dB. |
| frequency response | Range over which an audio component can effectively produce a useable and fairly uniform, undistorted output signal. |
| full power bandwidth | The range of frequencies across which an amplifier can supply its full power rating to a speaker. |
| full-range surround sound channels | A feature of 5.1 digital surround sound formats allowing discrete surround sound channels which are capable of playing across the frequency band audible to human hearing (20 Hz to 20,000 Hz). |
| function generator | A piece of test equipment that produces audio test tones from DC to well beyond human hearing. |
| gain | The amount by which an amplifier increases the power of a signal, indicated either in dB (e.g. Gain = +12dB), or as a multiplier (e.g. Gain = x4). |
| Gbps (Gigabits per second) | A digital information transfer rate of 125,000,000 bytes per second or 1,000,000,000 bits per second |
| ghosting | A video interference phenomenon where the video image may appear double and the second image will be faint, thus the term "ghost". |
| GPU | Ground Power Unit, particularly a power supply that converts AC power to DC power for running an aircraft's lights, instruments, and other systems while on the ground. |
| GPIO | General-Purpose Input / Output. These are extra connections on a device that can be used to interface with push-buttons, sensors, audio or video signals, or communication pathways. |
| ground (earth ground) | In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the earth. |
| H.264 | H.264 or MPEG-4 Part 10, Advanced Video Coding (MPEG-4 AVC) is a block-oriented motion-compensation-based video compression standard. |
| H.265 | High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, is a video compression standard, one of several potential successors to the widely used AVC (H.264 or MPEG-4 Part 10). |
| harmonic | An additional frequency in an audio signal derived from the fundamental or original frequency as a multiple of that fundamental that is smaller in amplitude (power) than the fundamental. |
| HD (High Definition) | A video format consisting of either 720 active lines of progressive video or 1080 active lines of either progressive or interlaced video. Offers the highest-resolution format. |
| HD Surveillance Cameras | HD video formats in security cameras adopt the formats found in HDTV broadcasts - primarily 720p, 1080i and 1080p. The number stands for horizontal lines and the letter specifies either progressive or interlaced scanning. All HD video formats utilize a 16:9 aspect ratio (widescreen) image. |
| HD-DVD | HD DVD (short for High Definition Digital Versatile Disc) is a discontinued high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format. |
| HDCP | High Definition Bandwidth Content Protection is an encryption protocol developed by the Digital Content Protection Organization to prevent the possibility of making high resolution copies of native digital audio/video content. It is an anti-piracy scheme to protect digital content owners. |
| HDCP (high-bandwidth digital content protection) | Specification used to encrypt and protect digital video and audio signals transmitted between two HDCP-enabled devices using DVI or HDMI connections. |
| HDMI (High Definition Multimedia Interface) | A digital audio-video standard that carries uncompressed video and audio signals on one cable from an HDMI compliant digital video source (Blu-ray player or satellite receiver) to a display device (HDTV or projector). This system provides better detail, color, and sound at potentially higher resolutions compared to analog transmission methods. It requires a special high-bandwidth HDMI cable with 19 conductors. |
| HDMI cable | Used for connecting HDTVs, digital flat-panel displays and other video components with HDMI connections to digital devices including DVD player, A-V receiver, soundbar, or other equipment with HDMI connections. Provides the best detail, color and sound. |
| HDTV (High Definition Television) | A television that accepts and displays high-definition video signals via terrestrial antenna, HDMI or Component Video transmission methods. 1080i/p and 720p are common HDTV formats. Ultra High Definition (UHD) TVs can display video formats up to 2160p. HDTVs are not merely video displays; they also accept and reproduce stereo audio via built-in loudspeakers, and usually have a built-in tuner for terrestrial broadcast signals. |
| headphone jack | An output connection on an audio or audio-video component which accepts a 3.5mm or 1/4 inch jack on a headphone cord. |
| headphones | Personal audio listening device which covers, fits onto, or inside a listener's ears. Headphones require different levels of amplification, depending on their purpose and electrical design. |
| headroom | An amplifier's ability to go beyond its rated average power for a short time in order to recreate loud or explosive audio signals that rise very quickly. |
| heat sink | A metal object, usually a row of thin metal fins, designed to dissipate heat away from electronic equipment. |
| Hertz | One cycle per second, kilohertz equals 1000 cycles per second, the accepted measure of frequency. |
| hertz | (Abbreviation: Hz) The unit of frequency. Replaces 'cycles per second' and means the same. |
| highpass crossover | Type of crossover that attenuates or cuts off low frequency signals and sends on only the high frequency signals falling above the crossover point (crossover frequency). |
| highpass filter | A circuit that discriminates between high and low frequencies and allows only the high frequencies to pass. |
| HLC | Prevents bloom (a large, washed out area around the light source) from bright lights such as sunlight, reflections, headlights, or flashlights, revealing more detail close to the source of the light. |
| horizontal input | Usually referring to the horizontal (X) input of an oscilloscope that measures an audio, I.F. or R.F. signal source. |
| HTML (Hyper Text Markup Language) | A scripting language used to create web pages for the Internet. |
| HTTP (Hypertext Transfer Protocol) | The protocol or foundation for data transfer on the World Wide Web (www). |
| HTTPS (Secure Hypertext Transfer Protocol | Hypertext Transfer Protocol Secure (HTTPS) is a variant of the standard web transfer protocol (HTTP) that adds a layer of security on the data in transit through a secure socket layer (SSL) or transport layer security (TLS) protocol connection. |
| IDC | Multi-pin keyed connector style for cable-to-circuit board connections. Used on power, high-level audio, and communications bus cables. Plugs or "headers" can be "thru" or "end" depending on the application. Common sizes are .156 for 18 and 16GA wire, or .100 for 24 and 22GA wire. |
| imaging | Term used to describe the quality of a sound field put out by an audio system giving a subjective measure as to how well a system can recreate depth, width and height from the recording. |
| IMAP (Internet Message Access Protocol) | A protocol to allow a user's email messages to be sent/received/managed on multiple devices. |
| impedance | The measure of the total resistance to the current flow expressed in ohms, in an alternating current circuit. It is an important characteristic of electrical devices (particularly speakers and microphones). Most speakers are rated at 4 or 8 ohms. Microphones are usually classified as being either high impedance (10,000 ohms or greater) or low impedance (50 ohms to 600 ohms). |
| input impedance | The measure of the total resistance to the current flow expressed in ohms, in an alternating current circuit at the input of a device. Most modern equipment has a low imput impedance from about 150 ohms to 600 ohms. |
| input overload distortion | Distortion caused by too great an input signal being sent to an amplifier or preamplifier. It is not affected by volume control settings and often occurs when mics are positioned too close to the sound source. This distortion is controllable through the use of an attenuator or pad. |
| input sensitivity | The range of input voltages required to produce outputs from the minimum to the maximum output of an amplifier; may also refer to the input sensitivity for maximum output, which is the input in volts required for an amplifier to create its maximum power output. |
| insulator | Material preventing the flow of electrons, making it suitable for prevention of unwanted current flow in electrical circuits. |
| integrated amplifier | An amplifier containing two stages: a 'Pre-Amplifier' and a 'Power Amplifier'. Commonly used for domestic hi-fi applications. |
| integrated amplifier | Audio component combining the elements of an amplifier with those of a preamplifier but not containing a tuner (making an integrated amplifier different from a receiver which does contain a tuner). |
| interconnect | Wire used to connect various pieces of equipment (components) in an audio/video system carrying audio or video information via low-level electric signals (not very powerful) or via light pulses (digital information carried over fiber-optic interconnects). |
| interface | A device which facilitates the linking of any two pieces of equipment or systems; or when used as a verb ('to interface'), the process of linking. |
| interlaced scanning | Picture display process that saves bandwidth by reducing the frame rate. It refreshes every odd line in one scan of the screen and then refreshes all the even lines on the second scan. Compared to a progressive scan signal refreshing at 60 frames per second, interlacing effectively delivers 30 frames per second, causing a noticable flicker on larger video displays. |
| inverse square law | The law that states that in the absence of reflective surfaces, sound pressure (or light) falls off at a rate inverse to the square of the distance from its source. In other words, every time you double your distance from the sound source, the sound pressure level is reduced by a factor of 4, or 12 dB. |
| iOS (AppleŽ mobile operating system) | An operating system used for mobile devices manufactured by Apple Inc. |
| IP | Internet Protocol. This acronym usually refers to an Ethernet network, telnet commands, or network address. |
| IP (rating) | Ingress Protection Rating. Dust and moisture resistance ratingsystemfor outdoor electronics, specifically surveillance cameras. The rating consists of two digits. The first digit is forsolidsthe second digit is forliquids.A rating of IP67 indicates water resistance for brief submersion, whereas IP68 indicates long term underwater operation. |
| isobaric | A type of speaker enclosure used for subwoofers and bass drivers which uses a small, sealed enclosure with two bass drivers facing each other (one inside the box facing out and the other outside the box facing in at its counterpart) and wired out of phase. |
