Acoustic suspension

The acoustic, or air suspension denotes a manner of installing drivers (usually subwoofers) inside a sealed cabinet and relying on the quantity of air trapped inside for generating the compression counter-force to push the cone back. Due to the fact that air has a more linear dynamics, the acoustic suspension is used especially for woofers with a longer excursion. Despite the lower efficiency of the acoustic suspension speakers, they can reproduce cleaner, less distorted sound and are a very popular choice.

Acquisition time

Represents the time it takes a GPS receiver to acquire the signals broadcast by the geostationary satellites and determine the initial position.

Active Loudspeakers/Subwoofers

The �Active� character of loudspeakers or subwoofers determines the fact that these units sport their own, internal amplification circuitry and require only a power source and an audio source in order to play. Active loudspeakers and subwoofers are sometimes chosen in favor of their passive counterparts because they require less installation/wiring time and knowledge and are thus easier to use in certain locations or by persons with less technical training.

ADC (Analog to Digital Converter)

Often referred to as ADC or A/D, the analog to digital converter is an electronic device that transforms the analog signal to digital signal, helping interconnecting the two kinds of technology/gear. You meet ADCs in your computer sound cards, studio equipment and musical instruments. The quality of an ADC will dramatically influence the quality of the transformed signal.

ADSL

Asymmetric Digital Subscriber Line - Is the technology that enables broadband Internet content to be delivered over existing copper telephone lines. A form of broadband technology known as DSL (digital subscriber line), ADSL refers to an internet connection where the flow of data being downloaded is disproportionate to the amount of data being uploaded. ADSL enables greater download speeds for the end user, meaning that video services run much more reliably, and is a more efficient use of broadband infrastructure for the internet service provider (ISP).

ADSR

ADSR is an abbreviation for Attack, Decay, Sustain, Release, the four parameters in a basic synthesizer. While Sustain is a level control, the Attack, Decay and Release are time and ratio-dependant parameters. When a key is pressed, the Attack determines the ratio with which it reaches a top level and the begins to fall at the ratio of the Decay parameter down to the level set by the Sustain value. This value is kept as long as the key is being depressed and will return towards zero by a rate set by the Release parameter.

Aftertouch

Aftertouch refers to the MIDI instrument world and determines the data which is sent as to a device after a hey has been pressed and is continuously kept depressed for a short period of time. The aftertouch data can be routed to other parameters, depending on the complexity of the MIDI machine (volume and all sorts of other effects). Aftertouch can be mono and record and transmit only the higher value among multiple keys stuck at the same time, or polyphonic � relaying separate aftertouch data for each key. The results of using aftertouch in MIDI can be most expressive and creative.

Almanac data

Refers to the data transmitted by each GPS satellite regarding the orbits and state (health) of every satellite in the network of geostationary satellites used by the global positioning system. Almanac data allows the GPS receiver to rapidly acquire satellites shortly after it is turned on.

Altimeter

Is an instrument used for determining elevation, as for example an aneroid barometer used in aircraft that senses pressure changes accompanying changes in altitude.

Ambient light

Ambient light is the light diffused in the environment surrounding a detector measuring the optical radiation from another source. This light contributes to the signal measured from the source. To make valid measurements, the contribution from the ambient light or background must be subtracted from each measurement.

Analogue broadcast

The term analogue broadcast refers to the traditional method of broadcasting TV and radio signals over the air or via cable. Information in the form of channels is transmitted in the form of radio waves with variable wavelengths.

ANSI Lumen

represents the standard measurement unit for the light output generated by a projectors (including here video projectors). Due to the fact that the center of the projected image is typically brighter than its corners, the ANSI lumen represents the the light output generated by the most accurate image. The ANSI lumens are generally measured by taking readings from different positions and then computing an average value. The term ANSI has been associated to the measurement unit mainly for commercial purposes, since said organization has developed a very accurate method of measuring the light output of a certain source (described above), and the luminous flux of projectors that have been tested according to this procedure may be quoted in "ANSI lumens", to distinguish devices that have been so tested from those tested by other methods.

Aperture

A hole through which radiant energy can pass. Angular aperture is the angle through which the most divergent rays can pass through a hole or lens. The aperture of a lens is often expressed in terms of an f/#. The f/# is the ratio of the focal length of the lens to its diameter. A lens with a focal length of 100mm and a diameter of 25mm would have an aperture of f/4.

Aspect ratio

Represents the ratio of image width to image height. Typically, motion-picture ratios are 1.85:1 and 2.35:1. Television screens are usually 1.33:1 (also known as 4:3), which is similar to the Academy standard for films in the '50s. HDTV is 1.78:1, or 16:9. When widescreen movies (films with aspect ratios wider than 1.33:1) are displayed on 1.33:1 televisions, the image must be letterboxed, anamorphically squeezed, or panned-and-scanned to fit the scre

Attack

Attack is defined as the period of time elapsed between the detection of a specified trigger and the actual response of a system or the time a system needs to react when its state has been altered. Attack is commonly met in compression/expander and limiting fields. In plastic depictions, attack is the time elapsed between someone pinching you and you screaming.

Audio Book

An audio book is a recording of book's content, read aloud by an actor or sometimes by the author. Audio books were usually distributed on cassette and CD support, while the modern technology now involves compressed formats like the MP3 or Windows Media Audio. Audio books can be abridged or unabridged, depending on their goal and production. Helpful for a more dramatic experience and at the same time very convenient for people with visual impairments, audio books are also serialized in radio shows.