How to Match a Complex Ambience Tone in Audio

ADR, dialogue replacement and good editing is hard to begin with, and without the right tools and recordings, it’s even harder. Matching Room Tone for Dialogue Replacement is hard enough, but what about more complex scenes? Is there an equivalent to ‘Room Tone’ for complex soundscapes like a construction site, a forest full of birdsong, or a road full of different vehicles?

In this article, we’ll show you how to match a complex ambience based on previous recordings and create variations of complex sounds you’ve already recorded.

It Starts with Undertone 2

Undertone 2 is our software for replacing and matching ambience for audio editing. It has different modes to work with simple ambience like room tone and more complex, multi-sound audio scenes. We’ll show you how to match a complex ambience using the plugin in Pro Tools, but the process is very much the same in other DAWs.

Using a Long Source to Recreate a Complex Ambience

Load your Existing Ambience. First we’ll assume that you have a recording of your ambience alone – sort of like ‘Room Tone’ but with more complexity happening in the source. We’ll work with a few files that are available from freesound.org so that you can download them yourself to follow along using Undertone.

Birds In A Cage On Antibiotics.wav by Angel_Perez_Grandi — https://freesound.org/s/52166/ — License: Attribution 4.0

Construction Site Ambience in Thailand.wav by YOH — https://freesound.org/s/170873/ — License: Attribution 4.0

Each of these files can be loaded into an instance of Undertone as a single sample in Slot 1. 

NOTE: Before importing a long and complex file, go to Undertone 2’s Settings and untick Enable Auto Voiced Selection.

When we press play in our DAW, already the plugin is recombining different parts of the audio automatically to extend it into an infinite length. This works like cutting and fading together small portions of the original sample, but Undertone 2 does this automatically, and you can change the parameters to make smaller or larger cuts, for example.

With these default settings, Undertone has done a good job when it comes to cutting up and reproducing the birds, as you can hear below…

…but when the default settings are applied to the Construction Site recording, things haven’t worked so well. Hear it below…

In each instance, Undertone has started processing one of these files using its Granular engine. This cuts the file up into smaller chunks and plays many of these chunks to blend into one. But the default size of the grains (slices) is too small, and so the plugin is chopping some of the personality out of the sounds experienced in the recording.

We can fix this by playing the sample using the Multi engine. With the construction site loaded, click Multi and also turn the dial between Single and Multi so that we have 100% Multi and 0% Single.

In Multi mode, Undertone lets us choose a Grain Size, which means our chunks or ‘slices’ of audio taken from the loaded sample will each be longer, and so the original whole sounds inside it (drilling, hammering and coherent footsteps, for example) will be reproduced better.

Useful options include the number of Grains (at the top), the Play From Start button, and the Panner, which can be switched on for more stereo variation.

The end result is a longer playback of the file, with overlapping grains that can draw things out to last as long as needed.

Using Multiple Short Files for Complex Ambience

And now, let’s use Undertone’s Multi engine by loading multiple sounds and making a larger scene. We’ve downloaded three sounds of cars passing from the freesound.org website.

car_25.wav by koirankarva84581682 — https://freesound.org/s/664766/ — License: Creative Commons 0

car8passing by fireflyhugz — https://freesound.org/s/714432/ — License: Creative Commons 0

passing car by NachtmahrTV — https://freesound.org/s/553259/ — License: Creative Commons 0

And we’ve loaded each into Undertone 2’s Multi engine, alongside one sample of background traffic noise to use behind them. 

With the parameters at the following settings, we’ve used each file’s probability settings, Grain Limit and Rest Time to make sure we have a background (played by the Single engine) and a foreground of cars that are generated occasionally, with variations in both pitch and level with each one. With the plugin, we can generate this ambience for as long as we need.

More on Undertone 2

Our software makes it easy to generate room tone and ambience from either dedicated room tone files or recorded dialogue with ambience behind it. Perfect for ADR and other dialogue editing duties, Undertone can save audio editors time and frustration in post production.

Take a closer look at Undertone here.