Intermediate Frequency. Wireless receivers normally convert the incoming RF signal to a lower intermediate frequency for amplification and final filtering prior to demodulation.

EIN is a specification that is mostly relevant to microphones and preamplifiers. It stands for Equivalent Input Noise and deals with the self noise that is a feature of virtually every piece of electronics. Since microphones output a low-level signal, any noise present will be boosted proportionately.

The initial sound reflections from walls, floor and ceiling, created when an acoustic event happens in an acoustically reflective environment. Often a parameter that can be adjusted in units that electronically simulate acoustic spaces (reverb processors.)

In wireless microphones, the radiation of an RF signal, whether intentional or not.

Originally design to add back some of the high-frequency content lost in audio production due to multiple passes using analog tape. Techniques used include dynamic equalization, phase shifting and harmonic generation.

All sounds can be described in a variety of ways. One of them is the manner in which a sound evolves amplitude-wise, starting from silence to full volume to final decay. Or how the harmonic content changes over time. In synthesizers, these changes to an oscillator or filter are achieved using envelope generators.

Hardware device or computer plugin used to alter the frequency balance of an audio source. An equalizer has the ability to boost or cut specific frequency ranges based around a center frequency and can be used either creatively, to drastically alter a source, or in a corrective manner, such as in a mastering situation, to even out anomalies in a mix.

Synthesizer with no keyboard, often rack mountable or in some other compact form. Useful for users who already have a keyboard and do want another one, but want the sounds offered.

In wireless microphones, the process of restoring the original dynamic range of the audio signal by means of a 1:2 logarithmic expander.

Field-Effect Transistor typically used as an impedance converter at the element in a condenser microphone. A MOSFET is a particular kind of FET, which is finding itself used more and more in power amplifiers.
(See MOSFET)