Today’s lesson Discovering and understanding compression Working on club dance portfolios

Compression Compression can be viewed as an automatic volume control. Compression reduces the volume of a loud signal and boosts the volume of quiet sounds by narrowing or “compressing” an audio signals dynamic range Common in music industry starting life controlling radio/broadcasting signals.

History of Compression The first dynamic compressor to be produced was the Telefunken U3 buit in the 1930’s and used in the 1936 Olympic games ’s – compression was developed to control the levels of radio/tv (with only in/out controls) – First commercial compressor ‘The Western Electric 110 limiting amplifier’. 1960’s – Most popular (even today) compressor the Urei/Universal Audio 1176 was released. 1970’s – The dbx 160 was considered by some to be the best VCA compressor. 1980’s – DAWS offered compression with sequencing software reducing need for rack mounted compressor units.

Limiters A limiter is a type of compression that uses a hard knee, combined with fast attack and decay times. Brick wall limiting has very high ratio and attack time. this insures the signal never exceeds the amplitude. (20:1 to ∞:1). Limiters are often applied to an entire mix to prevent clipping. It is also used as a safety measure to prevent damage to PA equipment.

Diagram showing how a signal is affected depending on the ratio setting. Diagram showing the difference between a soft knee attack, and hard knee attack.

Parameters Threshold – How loud the signal is before compression is applied. Ratio – How much compression is applied. For example, if the compression ratio is set for 6:1, for every 6 dB the signal exceeds the threshold, only 1dB will be let through. That is why a higher ratio has a more noticeable effect, because the dynamic range is being more compressed. Attack – how quickly the compressor starts to work once the signal exceeds the threshold. Release – how quickly after the signal drops below the threshold the compressor stops. Knee – sets how the compressor reacts to signals once the threshold is passed. Hard Knee settings mean it clamps the signal straight away, and Soft Knee means the compression kicks in more gently as the signal goes further past the threshold. Make-Up Gain – allows you to boost the compressed signal, as compression often reduces the signal significantly. Output – allows you to boost or decrease the level of the signal output from the compressor.

Here is a screen shot from the compressor plug in within Logic X. You can see here the various parameters mentioned on the previous slide. Compression explained - Video

Noise Gates A noise gate does as the name suggested and is used to either open, letting the audio in or close, to keep sound out. Traditionally it was used to minimize unwanted noise when recording using microphones (such as amplifier hum). When no noise was played the gate is closed as the noise does not exceed the threshold. When noise is made that exceeds the threshold this opens the gate, reducing the unwanted noise. Noise gates can be used to help separate different instrument, for instance reducing the kick track in the snare recording or live situation. Gates explained - video

Digital technology is less noisy than analogue therefore the need for gates as a corrective tool is less that in previous years. However noise gates can be used more as a creative tool. For example a noise gate can be used to trigger other sounds, such as a kick drum signal being side chain to trigger a snare, which forces the audio to synchronise.

Parameters Threshold: How loud the signal is before the signal is reduced. Attack: Sets the amount of time the gate takes to open after the signal exceeds the threshold. Hold: Sets the amount of time the gate is kept open after the signal falls below the threshold. Release: Sets the amount of time the audio attenuates for after the signal has fallen below the threshold.

Expanders Expanders have the opposite effect to compressions and actually increase the dynamic range. So a ratio of 4:1 will in effect be 1:4, for every 1 dB increase in input level there will be a 4dB increase in output. Expanders are often used to make quiet sounds even quieter.

Tremolo Tremolo is a modulation effect created by rapidly modulating the amplitude of a signal. Common parameters include: – Depth – Rate – Symmetry – Smoothing Tremolo demonstration within Logic Pro It is often used in various forms of dance music to create a ‘wobble’ on vocal tracks‘wobble’ on vocal tracks

Explain how compression and noise gates work, and various uses for their application. Include explanations of the various parameters found in each processor. Exam question