Audio Compression.docx

7/29/2019 Audio Compression.docx

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Audio Compression Tips for Mixing

http://www.audiorecording.me/audio-compression-tips-for-mixing.html

Professional Audio Mixing is basically two steps: EQ and Compression. Different instruments require

different compression scenario. To those that do not know what is compression, it is all about controlling

the peaks of recorded signal.

The easiest way to understand how compression can be useful to a mix is vocals. Vocalist even

professionals have tendency to sing very loud in some portions of the song. Now without compression,

this vocal track could be very annoying. Compression sets balance by automatically compressing signals

when it reaches a certain level.

My major rules in compression is simple, compression takes away signals and sound quality. It is a fact,

that if overdo it will drastically reduce the power of the sound.

Now let me give you my tips on compressing common instruments in audio tracks.

Compressing vocals in the mixI use the presets of Sony Wave hammer-Voice settings. This plugin is

available in Sony Creative Sound Forge 10. If you have this installed in your computer, since this a Direct

X plug-in, it can also be added to Adobe Audition or other DAW that accepts Direct X plug-in.

The characteristics of these compression settings are this:

Attack time- 5 ms

Release time- 50ms

Threshold- -10dB

Compression ratio5:1

Take note that attack time is very short, it is because vocals is highly transient in nature, the notes of the

vocal is very short, so to capture effective compression in vocals, one must set to short attack time. The

release time is a bit slow. It is because when a vocalist sings loud portions of the song, it will tend to last a

longer time also. It is an odd song to have a very short loud portion of the vocals. Threshold of the

compressor is the level of the signal at which compression starts. For vocals, I need it to set to -10dB

because more than -10 dB in vocals is already very dominative in mix. The compression ratio is 5:1; this

means a five times reduction in the signal when it reaches -10dB or above. Now thats a bit compression

to lower the volume of the loud peaks.

Compressing guitar in the mix: For acoustic and clean electric guitars, I use Sony wave hammer Guitar

presets. The compression settings are:

Threshold: -20dB

Ratio: 5.0 is to 1

Attack time: 15ms


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Release time: 15ms

The threshold is lower in volume compared to the vocals, the primary reason is that guitars need to sound

a bit lower than vocals in the mix or else it will dominate the vocals. Compressing at -20dB ensures that

any strong level above it will be suppressed five times to control the volume and not being too loud.

Guitar sounds are not sharp transients in nature unlike vocals, kick and snare. It will have a sustaining and

delaying sound. So a medium set attack and release time is good.

Compressing bass guitar the mix: Bass guitar sounds needs to be compressed to provide a steady beat

backbone to the song. This is very important in modern rock and pop tracks. And because of this, I use

Sony wave hammer Bass guitar presets with the following settings:

Threshold= -20dB

Ratio: 6 is to 1

Attack time: 40ms

Release time: 80ms

The main concept of creating a big bass sound is slow attack and fast release. This is because since bass

are not super fast transient it needs to develop its level first then set compressor to attack the signal and

release it immediately, the effect is a loud sounding bass. Compression settings is a bit higher than guitar

and vocals, because bass needs to be more uniform in sound to provide a steady beat.

Compressing kick drum in the mix : I do not compress kick drum in the mix because I want to sound real,

alive and not compressed. Compressing kick drums in my experience, takes away its deep bass sound so I

do not like idea of compressing it.

Compressing snare drumsSnare drums needs compression, so to compress snare I use these settings :

Attack: 20ms

Release: 40ms

Threshold: -12dB

Compression ratio: 5:1

Snare needs to sound natural even though it is sharp transient in nature I prefer to compress snare with aslower attack time and faster release. This will give a full snare and powerful sound. Compressing with

too fast attack time can flatten a sound and will make to sound dull.


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I am going to show you how I mix my vocal track in one of my songs. Before writing this guide,

I had read many articles and listened to podcast regarding vocal mixing. This article will be a

step by step guide with pictures and effects tweaking that I applied to my audio file. Before

mixing, lets assume that you already got a very good and clean vocal recorded. About how to

record a great sounding vocal track, it will be another post in the future. You will also find those

articles and references that I studied to accomplish this task at the bottom of this page.

This vocal track is retrieved from my own composition:

Original Song: Earnest

For easy illustration, I only use a few clips out of the 4 minutes track which is appropriate.

Original dry track:01-original-track.mp3

Dry means there is nothing added to the track, no EQ, no FX, no tweaking or anything else.The wave form looks like this:

Step 1: Cleaning Plosives

Plosives are the P and B wind problem. When there is Ph, B, or F sounds in the lyrics sung, a big

puff of air comes out and hits the microphone. It sounds like a kick drum noise. Look at the waveform that consist a puff noise.
http://pianologist.com/2007/03/29/original-song-earnest-%e6%87%82%e5%be%97%e8%ae%a4%e7%9c%9f/http://pianologist.com/2007/03/29/original-song-earnest-%e6%87%82%e5%be%97%e8%ae%a4%e7%9c%9f/http://pianologist.com/2007/03/29/original-song-earnest-%e6%87%82%e5%be%97%e8%ae%a4%e7%9c%9f/http://pianologist.com/2007/03/29/original-song-earnest-%e6%87%82%e5%be%97%e8%ae%a4%e7%9c%9f/http://pianologist.com/wp-content/uploads/2007/06/01-original-track.mp3http://pianologist.com/wp-content/uploads/2007/06/01-original-track.mp3http://pianologist.com/wp-content/uploads/2007/06/01-original-track.mp3http://pianologist.com/wp-content/uploads/2007/06/01-original-track.mp3http://pianologist.com/2007/03/29/original-song-earnest-%e6%87%82%e5%be%97%e8%ae%a4%e7%9c%9f/


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Try to minimize this problem during recording. Anyway, there will be some puff went through

unnoticed. With just the puff selected, apply an EQ that cuts by about 12db or so below 300Hz or

whatever sounds the best. If you catch it right, the nastiness will be greatly reduced withoutcutting the low end from the rest of the track. I did it with a low pass filter.

Puff noise:02-puff-plosive.mp3

Puff reduced:03-puff-plosive-removed.mp3

Step 2: Cleaning Silent Clips

In order to reduce noise level, chop out the silent part of the vocal clip. The result wont besignificant. But if you dont do this trick for every other audio tracks, the noise would be stacked

up significantly. I never cut out the breath sound. It makes the singing more natural. If you listen

to some Whitney Houstons songs, you will notice her breathing sounds so clear and crispy inthe recording.

Step 3: Smoothen the dynamics

There will be certain words sung unnaturally loud or soft making the dynamics sound uneven.

You can smoothen the dynamic, but dont overdo that it will take out the life of the vocal

performance. There are two method to achieve this:

use volume envelope: I personally think that using volume envelope is moretroublesome. But it all depends on your work habit and practice. Volume envelope can
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put in level gain or level cut and visually it is easy to achieve. It is also non-destructive.

When you hear that the envelope is not appropriate, it can be deleted easily.

use easy level gain or cut function: select the softer part, and boost it up 3dB or you cancut those louder parts 3dB. Most audio sequencer has this basic function. I prefer this

method because I can see the wave form smoothen out. Bear in mind that this function is

destructive. You can make a copy of the original track before you edit it this way.

Find the louder part of the clip:

Cut 3dB and smoothen:

Listen to the smoothen clip:04-smoothen-clip.mp3

Step 4: Fade in at the beginning of the clip, fade out at the

end

This step is not necessary. For some vocalist like me who cant really control my voice at the endof a sustaining phrase, it would be a good idea to fade out. This make it sound nicer and reduce

the glitch.
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Dry clip:05-not-faded-out-clip.mp3

Fade out clip:06-fade-out-clip.mp3I am sure that you can hear the difference. It is smoothen and more natural without glitch.

Step 5: Tuning the tone deaf

I dont suggest that you record someone who is totally tone deaf unless you want to try your

patience tolerance level. By the way, even the best singer sometimes sings a little bit out of tune.Nowadays, it is pretty easy to cure this out-of-tune disease with sophisticated effect plug-in.

Refer to the dry clip, you will hear that the first two notes are slightly sharpen. Even though it ishard to hear, but you can see it clearly in the Antares auto-tune FX.

Dry Clip:01-original-track.mp3

Use the FX to correct the pitch a little bit lower as shown by the yellow line
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Tuned clip:07-tuning-sharpen-note.mp3

Ok, now you realize the secret why some singer cant sing well live on stage but they sounds soperfect on the CD. In the studio recording session, all the vocals are fine tuned extensively before

it is duplicated into CD.

Add Effects (FX)

Now the vocal track is completely edited. The next big step is how to set up the proper effect

chain for the vocal track. I would like to emphasize that effect should be used conservatively and

subtly. As shared byBrian Redmond,Any constant effect loses its affect very quickly. Also,effects dont have to be complicated.

Step 6: Add Compression

Compressor is an effect which is hard to master. According toJoe Shambro,Compression does

two things for vocals. One, it can help a vocal tr ack stand out better in the mixby sitting better

within the overall mix itself. By compressing, youre making sure thatthe loud and soft parts ofthe vocals are even. Without it, the soft parts will get buried in the mix, and the loud parts will

overpower the mix. You want the vocals to have a nice, smooth sound in the mix. Second,

compressing brings out the tone of the overall vocal sound better, allowing it to make a better

impact.

In short, compressing a vocal track make it sound more stable, instead of appearing, and then

suddenly disappearing at softer part.

It will need another post to explain how to use the compressor. Here is the setting I use:

Start with the ratio setting 4:1 would be fine. Lower the threshold. Remember to add some gain

to compensate the level loss after compression. Compression effects is so subtle that it takesyears of experience to master the parameter setting such as the attack and release time.

Compressed clip:08-compressed-vocal.mp3
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Step 7: Equalizer or EQ

According toJoe Shambro, When EQing, theres two types of EQ. One is subtractive, where

youre removing a frequency to help others stand out better, and then theres additiveEQ, whereyou boost frequencies to help the overall mix. Personally, I prefer relying on subtractive EQ for

the lower frequencies, since additive EQ on the lower end tends to color the other frequencies ina way thats not too pleasing to the ear.Different vocalist need different EQ. For mine, the setting is shown below:

Bear in mind that any EQ more than 6dB will sound odd. However, there is no rules on this. You

can be as adventurous as you want. For me, I just boost a bit around 195kHz and cut some lowerfrequency.

Listen to the equalized clip:09-eq.mp3

Step 8: Reverb

We record the vocal preferably as dry as possible in an isolated room. But most of time we are

listening to natural voices which are filled up with thousands of delay and echoes, which is

known as the natural reverbs. So to make the dry vocal sounds more natural, adding some subtle

reverb is a must.I will write another post about reverbs effect in the future.

Listen to the clip with reverb:09-add-reverb.mp3

Generally, the two most important parameter is the mix level, and the predelay. Normally it isset to 10-30% wet. The predelay should be more than 100ms so that the reverb wont blur the

wordings.
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Paul Whitetaught me a great strategy on applying reverb to vocal,Traditionally, vocals are

treated using plate or room reverbs, but on

the cheaper hardware boxes and most plug-ins, the presets tend to muddy

the sound before they produce the desired thickening effect. Onestrategy that I have found to work well is to use a reverb algorithm

where the early reflections level can be adjusted independently of thereverb tail, then turn the level of the reverb tail down by around 6dB.The early reflections have the effect of thickening the vocal without

making is sound washy, and by turning down the level of the reverb

tail, you can still get away with a fairly long reverb time (typicallyaround 1.8 seconds) without losing clarity. Up to 100ms of pre-delay

also helps add depth without clouding the picture, and you may even be

able to drop the reverb tail level further if youre aiming for a more

subjectively dry sound. If you have a commercial recording in a similarstyle, keep this on hand as a reference when youre setting up the mix,

as it helps to compare generaltonality and reverb settings.

At last, now compare the unedited clip to the edited and FXed clip:

Dry unedited:01-original-track.mp3Final product:09-add-reverb.mp3

Finally, I would have to declare that I am not a master in mixing music. Because of tight budget,

I tried my best to DIY (do it yourself) my album. At the meantime, I love to share what I learnedfrom the process.

You are most welcomed to share whatever you know or pinpoint any contrast opinion about myapproach. Thanks!

Reference for vocal mixing:

Tracking and Mixing Vocals

Mixing with Ed Cherney: persistence is as important as gearPandora Mixing Vocal Podcast

Other related mixing tutorial:How to Fatten a Sound in a Mix

Technorati Tags:mixing vocal,vocal effects,how to mix vocal track,mixing vocal track
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Audio Compression.docx