Controlling Dynamics

Controlling Dynamics

1. Dynamics

   • Dynamics refer to the change of volume in a note
   • The level of sound is usually measured in dBs which is based on a logarithmic scale
     • 0dB is the lower threshold of human hearing and 140dB is the sound of a jet engine about 30m away
   • Control of dynamics is a vital part of recording, mixing and mastering

2. Compression and Limiting

   • History of compression
     • The world's first dynamic compressor was built in the 1930's
       • Telefunken U3
     • Used on radio broadcasts in the 40's and 50's
     • Valve tube compressor in 1959 created smooth, warm sound
     • Used as software plug-ins now
     • In the 60's it was used to keep dynamic levels under control but now it is used more creatively (e.g forcing rhythm in dance music)
   • What a compressor is
     • Automatic fader that reacts to sounds above a given level and reduces them by a set amount
     • Acoustic recordings often contain peaks determining the maximum SPL before distortion however by reducing the peaks, the whole recording level can be set higher
   • Controls
     • Threshold - this determines the sound level at which the compression is applied, sounds above it are compressed and sounds below are left
     • Ratio - once the sound level crosses the threshold, compression is applied at a settable ratio (e.g 3:1 means that the input has to increase by 3dB for the output to increase by 1dB
     • Knee - a hard knee means that compression is immediately introduced at the threshold but a soft knee means the process might begin just before the threshold allowwing it to reach the set level just after
     • Attack time - how long it takes to apply the compression after the sound has passed above the threshold
     • Release time - how long it takes for the compression to stop after the sound has dropped below the threshold
     • Input gain - adjusts the levels put into the compressor to avoid distortion
     • Output gain - (sometimes called make-up gain) allows the overall sound level to be brought up
     • Bypass switch - turns the effect off and allows quick comparisons to be made
     • Stereo link - two mono compressors to allow the L and R to have the same settings

3. Limiting

   • A limiter is a type of compressor that uses a hard-knee change at the threshold with fast attack and decay times
   • It lets very little sound rise above the threshold (e.g - 20:1
   • Can be used with a compressor to cut out the loudest peaks
   • It can lead to a particularly dead sound
   • It can be used as a safety measure to prevent damage to equipment and also be applied to an entire mix output to prevent clipping

4. Noise Gates

   • A gate opens to let a signal through and closes to keep it out
   • It is used to remove/minimise unwanted backgroud sounds
   • Thresholds have an attack and decay control but can also have a hold time control
     • This keeps the gate open a little longer to ensure decay is not too quick
     • Imagine an ADSR envelope
   • Applying a gate to the whole mix runs the risk of cutting quiet sounds needed to create a natural acoustic

5. Expander

   • This reduces the output levels for signals below a set threshold
   • The ratio works in the opposite way to a compressor
     • For example 4:1 would be 1:4 so for every 1dB increase there is a 4dB increase

6. De-Essing

   • This is used to remove harsh sounds of sibilants from vocals
   • It uses a combination of EQ and compression
   • The volume of the frequencies is reduced when the vocalist produces them

7. Ducking

   • Used by DJs and radio presenters
   • It involves reducing a signal on one channel when one is present on another channel
   • For example if spoken words need to cominate

8. Distortion

   • An unwanted change of signal produced due to it being overdriven
   • Can be a useable effect with pedals etc
   • The three main types of distortion are overdrive, distortion and fuzz

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