Brooks XB 22 Golden Section

A ratio of height to width to length of a room to achieve "good acoustics" and first recommended by the ancient Greeks. The ratio is approximately the width 1.6 times the height and the length 2.6 times the height

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.

Brooks Cinema XB 33 Amplification
An increasing of signal strength.

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.

Brooks QS 70 Half Step
A pitch difference of the amount that is present between adjacent keys on a piano.

Harmonics
Integer multiples of a fundamental frequency, the fundamental itself being the first harmonic, its first overtone the second harmonic, etc. Attributing to instruments, voices, etc. their distinctive timbre.

Interface
Any device that allows one unit to work, drive or communicate with another unit when they cannot do so by just feeding each other often because the units are manufactured by different companies.

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.