Room Tone: What is it? Why do we use it? How can we do it Better?
Learn how to match ambience and room tone when editing dialogue audio to seamlessly continue background noise and avoid broken up sentences
Making films is complicated, and recording audio for them is no different. At first, we make a lot of recordings, and later, we make a lot of edits. Room Tone helps make these edits less obvious and far more natural, covering up any edits or any new recordings added in post production.
If you haven’t recorded your own room tone, the intelligent features in Undertone 2 let you extract room tone from an existing recording. The plugin then makes a constant bed of sound that you can use as necessary to cover any chops or slices, and which you can put behind any newly recorded dialogue.
What is Room Tone?
Room tone, sometimes called ‘air tone’, is the ambient sound of an environment where audio is recorded, with no voices, movement, or any other sounds. You might be recording in order to capture voices, but in between, you’ll be able to hear the room tone, and if that room tone changes suddenly or cuts out, the effect will be noticeable.
Often, room tone is recorded on its own to use later in order to patch up edits done to dialogue. The reason is that the recording may be useful later, in post production, to add behind new dialogue recordings, making them sound like they were made in the same environment.
Those recording on a film or TV set may hear the phrase “Hold for room tone” or “air tone”. At this, everyone must be quiet in order for the ambient sound to be recorded on its own.
Hear An Example of Room Tone in Use, Before and After
In the first audio file below, an edit has been made, patching in newly recorded words that replace those on the original recording. The change in background tone is obvious, and a listener can tell that something new has been added. In the second recording, room tone has been used to obscure this transition.
What is Room Tone Used For?
Any recording of dialogue will have an ambient noise floor, but any dialogue replacement will often be recorded in a studio or a different space. When replacement dialogue (ADR) is added, the room tone from the original recording is used to cover changes, edits and chops in the recordings, matching the noise floor of the new recording with the old one, filling gaps in the ambient sound, and avoiding broken-up sentences.
Room tone is important because an audience would notice small changes and inconsistencies in background noise – especially in a loud cinema. Using room tone to fill gaps and ADR cuts means audio can be improved without introducing sudden silences, and the overall sound of the production will be more professional.
Covering up Edits With Room Tone
If a dialogue editor has access to a dedicated room tone recording or a large enough piece from the relevant clip, a section will be chopped out and placed behind a new recording, fading in as the previous recording fades out in order to make a seamless transition, as below. A plugin like Undertone 2 makes this even simpler, as we’ll show you below.
A pre-recorded room tone clip from the location being used to cover up a newly recorded piece of dialogue
How is Room Tone Recorded?
On a film or TV set, room tone is recorded using the exact same microphones that are recording the main dialogue. This is essential in order to match the room tone recorded incidentally behind the desired dialogue. Using a different microphone or microphone position would cause the room tone to sound different.
Room tone must be recorded on its own, so there may be a request to “Hold for room tone” while the tone is captured on its own for a 30-second or one-minute stretch.
How to Use Room Tone
Below we have a piece of dialogue recorded in a real space, containing ambience. We want to break it into two and insert some new dialogue in the middle. There’s a problem though: the new dialogue has been recorded in a cleaner environment, so when our mish-mash of recordings go together, it’s quite obvious when the original (with its room tone) drops out and the new recording (without room tone) cuts in from between 6 and 7 seconds..
Here, new dialogue has been added in post, but the new dialogue was recorded in a clean environment, while the main dialogue has room tone. Hear it below.
This is exactly where room tone becomes useful. We create a new track and we add Undertone 2. We load the original dialogue as a sample into Undertone 2, and immediately its Sample Editor selects regions without dialogue, helping the plugin to generate the room tone we’ll need. When we hit Play, Undertone is outputting a room tone sound based on the room tone in the original recording.
We can record Undertone’s output for just a little longer than the duration of our newly inserted dialogue, or use Undertone’s Render button when running as an AudioSuite plugin in Pro Tools, and fade this tone in with the original dialogue recording.
We render Undertone’s output to create a noise bed that we can fade with the original recording
The result is, a disguising of the dialogue we inserted, and the fades between clips lead to a seamless transition. Here’s the audio below to demonstrate.
What Level Should Room Tone be?
This could be a trick question, but maybe not. Your room tone should be the same level as any original room tone recorded at the source.
What about if you have the option to dial your room tone down, and reduce or increase its level throughout your entire dialogue track. How loud should room tone be in an ideal world?
The answer is that your room tone’s level should be placed where it’s loud enough to be heard and add a character of realism to a recording, but not loud enough to be noticed. Keep your room tone at a level where it would be suddenly noticed if it was removed – purely from its lack of being.
How to Record Room Tone
The best way to work with room tone in post production is to properly record room tone in the first place. This must be done on location, keeping the exact conditions as will be used in the dialogue you’ll be working with.
Record Room Tone Using the Exact Same Setup
Room tone changes with different rooms, different equipment and even in different positions, so the room tone recording should be made in the exact same setup as the dialogue whose room tone it will be matching.
- Use the exact same microphone
- Place it in the exact same location
- Ensure anything generating ambient sound (machines, etc) is in the state it will be while recording
Ensure Everyone and Everything is Silent
Usually on a film or TV set, the sign for silence is given by the phrase “Hold for room tone”. This could be arranged by the director but will often be requested or instructed by the sound recording team.
Record Room Tone for 30 to 60 Seconds
During this time, the conditions should be exactly as they will be during recording, and there should be no other voices or sounds being made.
How to Remove Room Tone from a Recording
Removing room tone from one recording can be a very valid part of the post production editing process. If two recordings have very different room tone profiles, and they need to be made to conform, then removing the room tone from one of them – or even both of them – will be part of the process.
To remove room tone from a recording, you’ll need to use a piece of software designed for this purpose. Unlike Undertone 2, which was created to analyze and generate room tone, the following software tools are designed to isolate and remove room tone and background noise.
Five Audio Software Tools for Noise Removal
Waves Clarity Vx and Clarity Vx Pro
Waves Clarity Vx and Clarity Vx Pro are powered by advanced AI technology tailored specifically for dialogue noise removal. The standard version offers a simple, one-dial interface for quick and efficient noise reduction, ideal for users seeking speed and ease of use. Clarity Vx Pro, on the other hand, adds deep control over processing with multiple layers of adjustability, including separate controls for ambience and tonal preservation, making it suitable for professionals who require detailed adjustments. Both versions deliver high-quality results, preserving vocal clarity and naturalness even in challenging audio conditions.
Veed.io
Veed.io provides a user-friendly, web-based audio editing platform designed for fast and straightforward noise removal in podcasts, interviews, and video content. Its drag-and-drop interface makes it accessible to non-technical users, while offering additional tools for basic editing and transcription. The noise removal process is automated, making it ideal for quick, low-effort workflows, though it may not achieve the nuanced, high-quality results of more specialized software. Its cloud-based approach is a bonus for users needing quick edits without installing software.
Audacity
Audacity is a free, open-source audio editor with a built-in Noise Reduction tool that allows users to manually capture a noise profile and fine-tune reduction settings. Its workflow is more detailed than automated solutions, requiring some trial and error to achieve optimal results. While its noise removal capabilities are not as advanced or transparent as those of premium tools, Audacity excels in accessibility and versatility, providing a range of audio editing features beyond noise removal at no cost. It is particularly appealing to budget-conscious users or beginners learning the basics of audio editing.
Crumplepop
Crumplepop specializes in simple-to-use audio plugins designed to integrate seamlessly with popular video editing software like Adobe Premiere and Final Cut Pro. Its noise removal tools are focused on speed and convenience, with minimal configuration required, making them ideal for video editors who need efficient solutions. Crumplepop’s algorithms aim to balance ease of use with quality, producing good results without requiring in-depth technical expertise. While not as customizable as iZotope RX or Waves Clarity Vx Pro, it delivers effective noise reduction with a strong focus on saving time.
iZotope RX
iZotope RX is a professional-grade audio repair suite renowned for its precision and versatility. Its Dialogue Isolate module excels at isolating voices from complex noise environments, while the Spectral De-noise module provides fine control over noise removal using spectral analysis. Both tools offer exceptional audio restoration quality, making them a top choice for demanding projects in film, broadcast, and music production. While the learning curve is steeper due to its detailed controls, the unparalleled results and flexibility justify the effort for professionals seeking high-fidelity restoration and nuanced adjustments.
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.