In this week’s post I’ll talk about the different ways to change the amplitude of your audio using either normalisation, compression or limit.
Every audio will have dynamic range, that’s the difference in amplitude between the loudest parts and quietest parts of the audio. This will occur naturally as you speak and you’ll see a difference in height of your waveform through your recording.
Two of the methods of adjusting your audio affect the dynamic range while one leaves it exactly in tact.
Normalising
This is the one which leaves the dynamic range in your audio. When you normalise you set a peak volume you want your audio to be at and your DAW will analyse your audio and find the loudest part. From there it calculates the difference between the loudest part of your audio and the level you set to be normalised to. The entire audio is then adjusted by that amount, whether up or down. In doing this the dynamic range is kept as both the loudest and quietest parts of the audio are adjusted by the exact same amount.
Compression
This does affect the dynamic range of your audio and is designed to make the difference between the loudest parts and quietest parts less. This can be used to make your audio an easier listen so you can set the volume and the loudest parts won’t be too loud but the quietest parts will be audible.
Basic compression works by setting a threshold, this is the volume which when exceeded causes the compressor to kick into action. Ratio is by how much the audio is compressed. The higher the ratio the more the compression but equally the less natural your voice will sound. For voiceover or podcasting it’s probably best to stick to 2 or under.
Attack and release are how quick the compressor acts when the threshold is exceeded and how long it takes to stop that action again. The faster the attack the quicker the compressor kicks in and the more likely you are to eradicate any peak spikes in your audio. Be careful also how you set the release otherwise you could end up with very boomy audio as a fast attack and release will cause the compressor to be constantly kicking in and out.
The final thing can be called two things, either output gain or make up gain. Both are the same. Output or make up gain is how much amplitude to add back to your audio after the compressor has finished it’s work. Compression will usually make audio more quiet so use the input or make up gain to add back some volume to your recording.
Limiting
Limiting affects the dyanmic range of your audio and does exactly what you’d expect. By setting a limiter you tell your DAW that your audio must not exceed a set volume. A limiter simply scans your audio and “cuts off” any audio that exceeeds the maximum amplitude you set. If you’ve recorded audio which peaks at -1db but you set a limiter at -3db the limiter will cut the entire audio at -3db.
Within Adobe Audition’s built in limiter there are also other settings. Input boost turns the limiter into a virtual compressor as it adds back volume to the entire audio by the amount you set while still ensuring no audio exceeds the maximum amplitude you set. Look ahead time and release time are virtually identical to the attack and release of a compressor.
I hope this helps you to understand the three different methods. All three will be useful whether you’re recording voiceover or podcasting but it’s essential that you understand the difference between how the three work.
