EASI: Pronounced like "easy," EASI is an acronym for Enhanced Audio Streaming Interface. Similar in many aspects to ASIO, EASI is a new architecture developed by Emagic and is designed specifically to standardize communications between Software and Hardware in professional audio applications. It is cross-platform and designed to meet the requirements of both hardware and software without the need for further implementation. Emagic hopes to create a new standard based around EASI architecture as they claim it is superior in several ways to ASIO. In an effort towards getting EASI architecture accepted, Emagic is presenting EASI as completely public, with no Non Disclosure Agreements needed. They hope it will "start a discussion" among music technology equipment developers about compatibility issues.
EBU: Abbreviation for European Broadcast Union. Created in 1950 to solve ongoing technical and legal problems in the European broadcast community, it has evolved to include its own television new network as well as standards making committees and regular publications of new developments to members. EBU has recently been highly involved in setting technical standards for things like HDTV, DAB (Digital Audio Broadcasting), and DVB (Digital Video Broadcasting).
Edit Decision List: A term we're seeing more frequently in the audio world with the advent of random access recording systems, an Edit Decision List (EDL) is simply a list of desired takes and edits that will be used from the master recording, along with notes on where the cuts and edits will be performed. EDLs are commonly used in post production and video work.
Efficiency: A measurement of how much of the input electrical energy to a speaker is converted into sound. The remaining energy is converted to heat. Most direct radiator speakers are 1 or 2 percent efficient; a horn-loaded speaker might approach 20 percent, some reach as high as 30 percent. High efficiency means that a lower powered amplifier can be used to produce the same level, but there is also a case to be made for less efficient speakers actually being more accurate due to better damping and less susceptibility to resonances.
EIA: Abbreviation for Electronic Industries Association. Founded in 1924, The EIA is a private trade organization made up of manufacturers which sets standards for voluntary use of its member companies (and all other electronic manufacturers), conducts educational programs, and lobbies in Washington for its members' interests. Many of the EIA standards are used as a measuring stick in equipment manufacturer's specifications.
Elco (or Edac): A brand and type (like Crescent wrench) of multi pin connector used in audio systems and equipment for connecting multi pair cable with one connector (instead of many). Elco is made in the U.S. and Edac is made in Canada and both come in many different varieties. They both come in 20, 38, 56, 90, and 120 pin configurations. There are male and female connectors (plug and receptacle in Edac nomenclature). The male connector can be identified by its polarizing pins on the plug, whereas the female has polarizing sockets. Either sex can have the actuating screw or the fixed nut for attachment. All that is required is that there is one each. On the back of an ADAT, for example, the Elco is a female 56 pin, with fixed nut. The cable you plug in, therefore, is a 56 pin male with actuator screw.
Electret: A type of microphone design, similar to condenser. Basically, there is a permanently charged plate in the mic element. As the diaphragm moves in response to sound pressure, it creates a changing capacitance with the plate. The big advantage to using electret (also called back-electret, or occasionally prepolarized condenser) technology is that it does not require an external polarizing voltage (battery or phantom power). In some cases, the microphone includes an impedance changing preamp that requires battery or phantom power, but the electret element itself does not require voltage. Electret mics can lose their charge in high humidity and high temperature environments, so some care should be used in storing and using them. If the electret loses charge, the mic's sensitivity will suffer, resulting in an reduced signal to noise ratio.
Embedded Servo: A technology which increases the usable data storage capacity of a hard disk drive and eliminates the need for thermal calibration (see WFTD archive Thermal Recalibration). Servo information is used to correctly position the read/write head over the data track. Embedded servo technology intersperses the servo (location) information with user data. Spaced along the data tracks, the embedded servo information allows all platter surfaces to be used for data. Each platter has some capacity taken up by servo information, but the net result is greater storage capacity with the same number of platters, and no need for thermal recalibration.
EMI: EMI (Electro Magnetic Interference) refers to interference in audio equipment produced by the equipment or cabling picking up stray electromagnetic fields. This interference usually manifests itself as some type of hum, static, or buzz. Such electromagnetic fields are produced by fluorescent lights, power lines, computers, automobile ignition systems, television monitors, solid state lighting dimmers, AM and FM radio transmitters, and TV transmitters. Methods for controlling EMI include shielding of audio wiring and devices, grounding, elimination of ground loops, balancing of audio circuits, twisting of wires in balanced transmission lines, and isolation transformers among others. Completely eliminating EMI in a system ranges from easy to nearly impossible depending upon the equipment and the environment in question.
Envelope Generator (EG): The envelope of a sound can be explained as a variation that occurs to it over time. How a sound starts, continues, and disappears in terms of pitch, harmonic content, and loudness is a function of its envelope. An envelope generator is a circuit or algorithm found in most synthesizers that provide a means to apply these kinds of changes to a sound over time.
EPROM: Pronounced EE-prom (almost rhymes with eon), this is an acronym for Erasable Programmable Read Only Memory. Various types of ROM (Read Only Memory) chips are used in many computers and synthesizers to hold instructions or other data (such as sound data) that the machine uses. ROM chips must be permanently programmed at the time of manufacture. While being relatively inexpensive, this can be a problem because all decisions about the data must be permanently decided at a relatively early stage in the design of the product. PROM or Programmable Read Only Memory has the ability to be programmed at any time. The only caveat being that once programmed, the data is permanent. EPROM chips can be erased by subjecting them to ultra violet light radiation. This means they can be reprogrammed and reused as needed, hence the name EPROM.
Equal Temperament: There are many different scaling or tuning systems that define how individual notes are tuned in relation to each other. Equal Temperament is a Scaling system where the octave (see WFTD archive octave) is divided into 12 equal parts. The ratio of the frequencies between any two adjacent notes is exactly the same. Most keyboard instruments are scaled in this manner.
Equalizer: Based on the root word, equal, an equalizer is an audio device whose function is to equal out the tonal characteristics of a sound. At least that was the idea back in the days when they were first conceived as a tool used to get flat response in telephone lines and to make up for the deficiencies in audio equipment and acoustic spaces. Nowadays it could more aptly be named an "unequalizer" since they are more often used creatively to alter the relative balance of frequencies to produce desired tonal characteristics in sounds. An equalizer has the ability to boost and/or cut the energy (amplitude) in specified frequency ranges by employing one or more filter circuits. There are many different types of EQ's in use today in many widely varying applications, but they fundamentally all do the same thing.
Equivalent Input Noise (EIN): A rating of the overall noise performance of an amplifier (typically a microphone preamplifier). Basically, this is a measure of how much noise a mic preamp will add to a microphone's signal. Measurements are normally made with a 150 Ohm resistor on the preamp to simulate the load a mic would present. The theoretical limit on EIN is -130.0 to -131.8 dBm (the thermal noise generated by the resistor). When comparing this spec, keep in mind that larger negative values are better (i.e. -124 is better than -118). But don't place TOO much weight on this spec, most current EIN specs are infinitesimally small (can you REALLY hear the difference between -120 dBm and -122 dBm??)
Expander: The opposite of a compressor. Where a compressor takes a given dynamic change and reduces it, an expander increases it, making changes larger. Expanders are used to "un-do" compression in some circuits (companding). More commonly, expanders are used for noise reduction. In this application (downward expansion), a threshold is set at a level below desired audio signals, but above the noise floor. When signal drops below the threshold, expansion is applied, pushing signal even further down, reducing the level of noise. For example, an expander might be set up with a 1:6 ratio. This means that for every 1 dB of input level change the expander sees, it will output a 6 dB change. When a signal drops below the threshold by 2 dB, the output of the expander will drop by 12 dB, similarly dropping the level of any background noise floor. (See also "Compressor" and "Ratio" in the WFTD archives).