Do you apply your audio effects to an audio clip or an audio channel? The answer is, of course, it depends entirely on what you’re trying to achieve. Special effects might be applied to certain scenes, certain clips – whereas more global tasks such as sweetening, enhancing and mastering ADR would require effects placed on an entire audio channel. In a word, audio channels give you consistent and coherent processing in post to help unify audio collected from different sources.
Are the Top Down View
It’s true to say that preparing channels to better receive audio clips, no matter the source or content, is a vital time saver, and not only that, can be a quick fire way to ‘standardising’ a multitude of clips into one coherent sonic space – every sound is sat in one room, within the same four walls and not spread out over various psychoacoustic planes.
Set Up A Channel EQ Template
We use templates to save time but also to unify our workflow and create succession. The way we create is ‘our’ way, and over time we build strong methodology to that effect. EQ, being your forever-friend in post, can be used to very subtly clean, contour, polish and embellish within audio channels, not just individual clips.
- Insert an EQ on your audio channel, or set up your in built channel EQ
- Cut all frequencies below 20Hz and, depending on how your ears perceive the very low end of the audio source, cut everything below 50Hz. Do this by engaging the ‘High Pass’ control. The effect is an ‘unclogging’ creating a subtle openness especially in location recordings and environmental ambience.
- Sound effects such as street noise, a crowd softly murmuring in a cafe, birds singing, distant thunder, the engine of a war class submarine – Each of these effects can benefit, with maybe the exception of the submarine, from having the ‘sub’ frequencies removed. As always, use your ears and become sensitive to sensation, as apposed to just experience.
Warmth, Tone And Punch
Warmth is a generic word for the fullness and body in audio sources. It’s logical to say that subtle warmth achieved across each audio channel will result in a warmer final mix. With EQ, we require a small ‘shelf‘ lift in the low frequencies that sit above the sub frequencies such as 80Hz to 180Hz. This is where the ‘body’ of a rapturous roll of thunder lies, this is the thickness in the ‘thud’ of a suicidal corpse or of a felled tree. Used subtly, and with care it can be applied across audio channels globally.
- Engage a band in your EQ and set it to a ‘low shelf’. Between 80Hz and 180Hz. Your shelf should roll off, finishing around 200Hz.
- With channel EQ, subtlety is key. Set your shelf EQ from between +1.5dB amd +3dB only.
- For extra punch, you can add a ‘bell‘ boost in the low range from 60Hz to 100Hz. The ‘bell’ shape is a curve that centers around one particular frequency and is much more accurate that the long flat ‘shelf’ type EQ. Anything from +1dB to +6dB can improve on thin, porous sounding audio.
- Be cautious when using strong, sharp ‘bell’ curves boosting frequencies on audio channels. Sharp boosting or cutting is a technique best used on individual audio clips on a case by case basis. Use broad, subtle lifting and cutting on audio channels.
Compression And Control
Compression is available as a built-in audio channel effect in most NLEs for a reason. The dynamic reduction of loud signals needs to be automated by compression, otherwise we would be lumbered with the arduous task of manually keying in level reduction as that tree fell, or thunder clapped across the shivering torpor. It’s worth mentioning at this point that the effect of compression is a sensation more than a sound. For example, 10 channels each with with heavy compression settings will ‘feel’ very different (almost suffocated) to channels where no compression is used. Apply compression when audio is dynamic – i.e. really quite to really loud in short bursts.
- Insert a compressor before the EQ plugin on your audio channel, or engage the in-built channel compression
- One benefit of the compressor is called ‘makeup gain’. It adds character to audio by lifting levels back up after compression reduction
- Set your ‘Attack‘ to slow – somewhere between 0.30 and 0.80 seconds.
- Set your ‘release‘ to fast – somewhere between .5 and 50 milliseconds
- Set the ‘makeup gain’ on your EQ plugin to +1.5dB
- Set your threshold using your ears. During playback slowly lower the threshold control until you hear the dynamics (freedom, airyness, openness) of the audio compress and reduce. The point is to bring loud sources under a general control, give them a character and a flavour. You’ll notice audio straight from a DSLR camera of an excitable football crowd feeling chaotic, out of control and too dynamic
- Try to aim for no more than -3dB reduction on average. If you are compressing much more than this, then consider applying compression to individual clips on a case by case basis and not as a global channel effect.
Stereo Sound Stage
When mixing a number of audio sources together – street ambience, car horns, footsteps, weather sounds, dessert rain falling on corrugated cabins, the war cry a rogue interstellar mercenary, for example, it’s important to pay attention to the available sonic sound stage. Setting predefined pan positions can help to separate sounds, and the frequency spectrum they are comprised of allowing you to see and locate each before you begin EQ and compression. Will a cyclist moving at speed from left to right across a scene need panorama? With a stereo recording, no – that movement is embedded inside the stereo information of the audio recording. Foley, or mono sound replacement will need more care, and also creativity.
Here are a few techniques to experiment with panorama on your NLE audio channel
- Set your pan control no more than 85 full left or 85 full right as extreme panning can sound very unnatural to the ear.
- For sound sources with no apparent visual location, such as a bird chirping, a plane passing overheard, a fracas in some distant part of the city, pan can be set up randomly. Bear in mind, due to ‘panning law‘, audio can sound quieter and louder depending on it’s extreme panoramic position
- By making a copy of your audio channel, effectively doubling your audio source, panning channel 1 to the left 85 and channel 2 to the right 85 and setting channel 1 to delay playback 20ms can create ‘Pseudo Stereo‘ effects. Although Pseudo Stereo can sound quite cheap compared to natural stereo when used very subtly, way back in a mix, it can be a colourful psychoacoustic ‘bed’ for a richer, more immersive sound stage.
- Sounds don’t often move the way objects do. Panorama is about binaural psychoacoustic location and so, during playback, use your ears to place sounds in natural spaces, or use artistic license to bring believeablility to surreal, post-human soundscapes.
There’s a large emphasis placed on workflow in post and while setting up audio channel templates does address this, it should part of a larger, more personal methodology. Take away some or just one of these techniques and inter-lock them into your own daily practices to help streamline your NLE audio channel.
I hope this article helps you approach audio channels and audio clips differently, priming your project ready for audio post production… let us know how you get on!
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