| jack | Female audio receptacle, or socket designed for male plug. |
| jacketed wire | Insulation separates conductor, electrically and physically, within a cable. |
| JPEG | Short for Joint Photographic Experts Group, and pronounced jay-peg. JPEG is a lossy compression technique for color images. Although it can reduce files sizes to about 5% of their normal size, some detail is lost in the compression. |
| jumper | Used to connect multiple speaker binding posts on speakers capable of bi- or tri-amping. |
| jumper cable (audio) | Used to connect one audio device to another using shielded cables. Comes in the form of balanced or unbalanced configurations. |
| keypad | In a multi-zone audio system distributed in multiple locations around a home or building, a keypad allows a person to control the volume and other aspects of audio being sent to a specific zone in which the keypad is located. |
| kHz (kilohertz) | One thousand cycles per second. |
| kbps | kilobits per second (thousands of bits per second) a measurement of bandwidth. Digital audio formats, like MP3, are measured in kbps to indicate low or high bit rate. The higher the bit rate, the better the sound reproduction. Can be written Kbps or kbps. |
| late reflections | Sound waves that bounce or reflect off room boundaries and objects reaching a listener a relatively long time after the direct signal from the sound source reaches the listener. |
| LCD (Liquid Crystal Display) | A display that is made of two polarizing transparent panels and a liquid crystal solution that is between the two panels. As an electric current passes through the liquid, the crystals align so that light cannot pass through them. The crystals act like a shutter, either letting the light through or blocking it. The design of the transparent and dark crystals form the image. |
| leads | Signal-carrying cables used to connect various pieces of equipment. |
| LFE | Low Frequency Effects channel. An audio track specifically intended for deep, low-pitched sounds ranging from 3-120 Hz. The LFE signals are connected to a subwoofer that is designed for low-pitched sounds. |
| limiter | 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 "Peak Limiting") |
| line conditioner | Electronic device that "cleans" the electricity coming from a wall outlet to be used by audio/video components and protects them from electric spikes and surges. |
| line level | A signal whose voltage is between approximately 0.310 volts and 10 volts across a load of 600 ohms or greater. |
| linearity | Linearity is the behavior of a circuit, particularly an amplifier, in which the output signal strength varies in direct proportion to the input signal strength. In a linear device, the output-to-input signal amplitude ratio is always the same, no matter what the strength of the input signal (as long it is not too strong). |
| Linux | An open-source operating system modelled on UNIX. |
| lossy compression | A type of data compression which permanently discards data that humans supposedly "cannot hear" to create much smaller audio, video and image file sizes. When the file is decompressed by the recipient, this compression method replaces the data for the sections it removed with calculated values to restore the file. The decompressed file is similar but not identical to the original file. |
| lowpass crossover | Type of crossover that only allows low frequencies to pass cutting off or attenuating frequencies above the crossover point (crossover frequency). |
| lowpass filter | A circuit that discriminates between high and low frequencies and allows only the low frequencies to pass. |
| luminance | The portion of the video signal carrying brightness. The human eye is far more sensitive to changes in brightness versus changes in color (chrominance). |
| lux | A measure of perceived light intensity. Minimum light level for video cameras at which the camera records a satisfactory image. Good low-light capability = lower lux rating. |
| M2TS | A filename extension used for the Blu-ray Disc Audio-Video (BDAV) MPEG-2 Transport Stream (M2TS) container file format. It is used for multiplexing audio, video and other streams. This container format is commonly used for high definition video on Blu-ray Disc and AVCHD. |
| M4A | M4A is a file extension for an audio file encoded with advanced audio coding (AAC) which is a lossy compression. M4A was generally intended as the successor to MP3, which had not been originally designed for audio only but was layer III in an MPEG 1 or 2 video files. M4A stands for MPEG 4 Audio. |
| MD | MiniDisc is an obsolete Sony technology for digital audio storage. |
| MDF | Medium Density Fiberboard is used in Audio Authority workboard systems for retail demonstrations. Specify fire rated or un-rated. |
| megapixel | a unit of camera resolution equivalent to one million pixels, abbreviated MP. 1280x1024 is an example of a common 1.3MP resolution. |
| microphone | A device that converts sound pressure variations into electrical signals. |
| midrange | The middle part of the audio frequency spectrum above Bass and below Treble. |
| MiniDisc | MiniDisc is an obsolete Sony technology for digital audio storage. |
| MKV | Matroska (MKV) is a multimedia standard that holds an unlimited number of audio, video and subtitles files within one file format. |
| modulation | A method by which information (typically audio) is superimposed on a signal that carries that information. Examples of modulation schemes would include "AM" (Amplitude Modulation), "FM" (Frequency Modulation) etc... used in broadcast, amateur radio and non licensed radio services. |
| Molex | Molex is a large manufacturer of electronics plugs and sockets that dates back to the 1940s. Since it was one of the first companies to make these connectors, the Molex name has stuck, even though they are also made by others. |
| mono | Consisting of only one channel. |
| MP3 | Written MP3, or in filenames, .mp3: the file extension for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (that, in the opinion of the developers, the human ear doesn't hear anyway). It also adds an algorithm that increases the frequency resolution 18 times higher than that of layer 2. The result is mp3 encoding shrinks the original sound data from a CD by a factor of 12 without sacrificing sound quality. |
| MP4 | MPEG-4 Part 14 or MP4 is a digital multimedia container format most commonly used to store video and audio, but it can also be used to store other data such as subtitles and still images. Like most modern container formats, it allows streaming over the Internet. |
| MPEG | Short for Moving Picture Experts Group, and pronounced m-peg. The term also refers to the whole collection of digital compression standards and file formats developed by the group. |
| MPEG -1 | Video compression format developed by the Motion Picture Experts Group using perceptual coding and predictive technologies to eliminate data from an audio/video signal and thus encode it into a smaller size. |
| MPEG-2 | High-quality audio/video compression format developed by the Motion Picture Experts Group using perceptual coding and predictive technologies similar to MPEG-1 but including a higher bit-rate and more control over the compression and technology. |
| multi-room (audio and video) | An audio or audio-video system that distributes sound and/or video signals to speakers in multiple areas. In its most basic form, a multi-room audio setup contains a source component, like a receiver, and is connected to speakers in at least two different rooms. A complex audio-video multi-room system can include multiple video and audio sources, a matrix switching system, a centralized audio amplifier, and video displays with speakers in each room. These systems are often integrated with professional home automation systems. |
| multimedia | The use of computers to present text, graphics, video, animation, and sound in an integrated way. |
| mute | No sound or a cessation of all sound; a single button or control to cut off an audio signal and stop the production of sound. |
| noise | Typically low-level electrical distortions and interference created in an electronic component from power supply hum, interactions between internal electrical components, etc. (See also White Noise, Pink Noise and Brown Noise.) |
| noise reduction | Effort to reduce noise in a system, typically in sound reproduction equipment and sound storage media such as audiocassette tapes, through various mechanical and software based methods (see Noise). |
| non-linearity | Non-Linearity is the behavior of a circuit, particularly an amplifier, in which the output signal strength varies in indirect proportion to the input signal strength. In a nonlinear device, the output-to-input signal amplitude ratio is always different, and can vary with the strength of the input signal. Usually an undesirable condition. |
| non-lossy compression | A form of data compression which seeks out chunks of data which are identical, replacing them with markers called keys. In this way, the file is reduced in size, and when it is decompressed by the recipient, the keys are replaced with the large chunks of data that were originally there (this is called Run Length Encoding). Using non-lossy compression, the uncompressed file is identical to the original file. |
| notch filter (audio) | Filter used to eliminate a specific interfering or undesirable frequency by attenuating a very narrow audio passband from the desired signal. |
