Brooks GT 44 Amplifier (Power amp, Head)

It's the part of the sound system that actually magnifies or "amplifies" the sound. In other words, it makes stuff louder.

Distortion
Usually undesirable result of overloading sound equipment. Reducing the levels can remedy the situation.

Brooks Speakers Assistant Engineer
A less elevated version of the term Second Engineer. Experienced seconds often place microphones, operate tape machines, break down equipment at the session end and keep the paperwork for the session.

Expansion
The opposite of compression; for example, an expander may allow the signal to increase 2 dB every time the signal input increased by 1 dB.

Brooks Cinema Projectors CD (Compact Disc) :
1) Digital sound storage medium. Provides a high quality source of music, sound effects etc. Also used as a playback medium for sound effects etc. by large theatres with long running shows, although CDR (Recordable CD) is becoming more affordable by the day.
2) An abbreviation of the term Compact Disc (a small optical disk with digital audio recorded on it).

Inverse Square Law
Simply stated, the fact that in an un-obstructed area (like an open field) the sound pressure level will drop to half-pressure (-6 dB) every time the distance to the sound source is doubled.

Equalizer (Parametric, Graphic)
This is used to filter out and adjust specific frequencies in the PA. This is the part of the PA where you have the most control over the band's overall sound. It is also the number one weapon against feedback.

Fundamental
The tuned frequency and (almost always) the lowest frequency that is present in the sounding of a pitch by a musical instrument.