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Wednesday, July 24, 2013

Audio compression & limiting

Every sound is born out of silence, dies back in silence and during its life span surrounded
  Silence enables sounds to be It’s an intrinsic but unmanifested part of every sound.
                                                       Eckhart tolle

Audio Compression

It  is a Form of automated Gain control that reduces dynamic range of sounds. Audio Compression is one of the most important music production techniques used by many producers and sound engineers around the world for the purpose of enhancing modern music. Compression and limiting gives drum kicks the thump makes bass fat it creates space for the target sound to be.
Compression can be used to elevate quite zones by maintain of the louder parts usually at 0-db or at certain threshold so they won’t clip and cause distortions that would shade on the quite parts or increasing the gain of a sound when it falls bellow certain threshold.
Compression reduces the dynamic range of sound whether we are boosting or limiting the incoming signal this is because the natural range of sounds will be manipulated so it won’t fall between a certain point or rise above a certain point so the dynamic range of sounds has become static range of sounds. 

Software vs. analog compressors

It best to use both analog and software compressors together for maximum results software (plug-in) compressors are usually good for boosting frequency while analogs are best for successfully killing a signal if you are serious about music production you must consider buying analog compressors it makes you more professional in the field and it’s also one of the iconic tools in a recording studio.


Types of compressions



Limiting is a form of heavy compression applied over compression ratios greater than 10:1 it is used to enhance the track without causing any distortion the purpose of limiting is to set the output level to maximum usually to 0db to avoid clipping in the final mix .limiting is similar to audio compression except that in order for the limiter to work the signal has to reach the predetermined peak so when it reaches the predetermined peak it will fall back to the desired level usually 0db.

 Side chaining

Side chaining is a form of compression mostly used to mix the bass with kick to give it the natural sense (bouncing) of mixing between the percussion and the bass that’s when the percussion reaches its peak the bass or the lead linked to the kick would fall to a certain level to create the blending of the instruments with rhythm.

Parallel NY compression

Parallel compression is a mixing of unprocessed raw signal with its copy of highly compressed form this is done to increase the average volume of the quite parts without totally changing the whole dynamic range of the original sound.its best used on percussion instruments This can be done with allowing the unprocessed signal on one free channel plus allowing the over compressed signal on another channel.

Serial compression

Serial compression is a type of compression in which compressors are arranged in a signal chain while one compresses a specific band spectrum the other stabilizes the dynamic range of the sounds this helps to modify the sound in a more radical way than the parallel compression.

Multiband compression

Multiband compression is when a signal in divided in to different band passes such as low, mid, high frequencies in turn these frequency spectrum can be worked on individually we can select and silent a troubling frequency and vice-verse multiband compression is best carried out on the master channel for mastering purposes only if not could generate complexion when you try to make changes later.

also read about  using fruity multiband compressor for better final mix quality  




Noise gating

Noise gating is a muting of a signal when it fall under a certain threshold its used to prevent a low-level humming or hissing sound in the final record you can also divide the sounds In to their respective band spectrum and gate the band pass who’s causing the problem.



Ducking is a the lowering of a signal in the presence of another the same rule as the side chain compression is applied here ducking is used in voice over tasks when recording when the accapella kicks in the back ground instruments fall down to a certain level leaving enough head room for the accapella or when a dj on the radio announces something the sound he was playing would fall back to a certain point such this effect is called ducking. 



It’s used to limit high frequencies of those of vocals by recording artists from exceeding a certain limit to prevent (sibilance)

Types of hardware compressors

  • Tube compressors: these are earliest types of compressors and they have slow attack and release response times.
  • Optical compressors: uses element that radiates light which initiates the optical cell to attenuate the amplitude of the output signal. It also uses tubes for gain maximization.
  • Field effect transistor (FET compressors): would recreate the tube effect with transistor circuits. They are known to be fast and reliable.
  • Voltage controlled amplifier (VCA compressor): uses solid state integrated circuit system its more advanced in technology than the others it’s pretty much similar to digital compressors it’s just its hardware equipment. 

Compressor knobs and their functions

  • Threshold knob: is the level of gain where the compression starts to have an effect let’s say if the threshold set to 2 db then when the input signal exceeds 2 db compression s starts to take place it’s also Should be adjusted according to the incoming input level and type of audio component.
  • Ratio knob: ratio represents the amount of gain reduction carried out once the threshold limit has been reached if set out compression ratio to 4:1 the input signal increases by 4 db the output signal increases by 1 db, 1:1 is called a unit gain since there is no compression and heavy compression greater than or equal to 20:1 is known as limiting.
  • Knee knob: it’s the knob where we manage the effect of the compression ratio since knee governs how the signal transforms from uncompressed state to fully compressed state soft knee allows for a smooth transition while hard knee causes rapid transformation.
  • Attack time: controls the time required to reach full compression once the threshold has been reached.
  • Release time: controls the time required to halt compression once the signal has gone below the threshold level.
these are the most important parameters in audio compression

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