Close the distance first, angle second, and change the room third; if closing the distance does not bring the voice 15 dB above the floor, no position will save the take.
Place a microphone to trade room noise against voice quality
checked 2026-09-16responsible Room Tone Register (a named register, not a person)
The two knobs
Distance changes the direct sound by 6 dB per halving. Angle changes the room's contribution by the microphone's off-axis attenuation. Those are the only two controls that do not change the room itself, and both of them change the voice you are capturing. Distance adds proximity effect and a more coloured tone; angle adds off-axis colour to whatever still arrives. There is no setting that preserves the voice exactly and removes the room.
| Distance | Voice at 1 m reference | Room | Margin | Verdict |
|---|---|---|---|---|
| 2.0 m | 62 dB | 38 dB | 24 dB | Thin, roomy, usually unusable |
| 1.0 m | 68 dB | 38 dB | 30 dB | Workable if the talent projects |
| 0.5 m | 74 dB | 38 dB | 36 dB | Comfortable; watch proximity |
| 0.25 m | 80 dB | 38 dB | 42 dB | Very safe; heavy proximity, visible mic |
| 0.15 m | 84 dB | 38 dB | 46 dB | Lavalier territory; clothing noise becomes the limit |
The order to work in
- Set the distance from the voice to the mic. Aim for a margin of at least 25 dB above the floor for a normal speaking voice.
- Angle the microphone so that the loudest reflecting surface is in its least sensitive direction. Use the off-axis table rather than intuition; the difference between 90° and 120° is 4 dB.
- Only then treat the room. Treatment changes the room's contribution, which is the term that has not moved so far.
- If step one cannot reach 25 dB, stop. Change the room, change the time of day, or change the location.
The stop rule
A margin under about 20 dB means the floor is within 20 dB of the voice, and after compression and level-matching for delivery, the room will be audible under the dialogue. This is the sentence the register is prepared to defend against a director who wants the wide shot: the wide shot is a lighting and framing decision, and it is being paid for in the audio.
A lavalier at 0.15 m is not automatically better than a boom at 0.6 m. It has a larger margin against the room and a much smaller margin against clothing, jewellery and chest resonance. Compare the two, do not assume.
Source log
- 01Loudness and the decibel, UNSW Music Acousticssupports the perceived-loudness reasoning behind the 25 dB margin figure
- 02Helmholtz resonance, UNSW Music Acousticssupports the resonance behaviour of an enclosed volume, which is what a small room is
- 03Musical notes and frequency, UNSW Music Acousticssupports the frequency relationships used when comparing a voice spectrum with a room's
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Leave this page Close this page when the margin is above 25 dB. Below that, placement is no longer the tool you need.