Put a helper with a mirror flat on the wall and move it until the talker sees the microphone in it — that is the first reflection point; cover it with a panel deep enough for the lowest frequency you need.
Treat the first reflection with the mirror method
checked 2026-09-16responsible Room Tone Register (a named register, not a person)
Find the points
- Have one person sit or stand where the talker will be. Have a second hold a mirror flat against the wall.
- Slide the mirror along the wall until the first person can see the microphone in it. Mark that spot. That is a first reflection point.
- Repeat for the other side wall, the ceiling, and the floor. Four to six points is typical for a single talker.
- Repeat for the second position if there is more than one talker. The points move.
Size the panel
Depth is set by the lowest frequency you need to absorb, using the quarter-wavelength relation in the formula strip. Area is set by how much of the reflection you need to remove. In practice the useful target is covering the marked points with panels of at least 0.6 m × 1.2 m, which is the smallest size that behaves as a panel rather than as an edge.
| Panel depth | Absorbs from about | Typical use |
|---|---|---|
| 25 mm | 1.5 kHz | Top-octave only; rarely worth it |
| 50 mm | 1 kHz | Bright-room fix |
| 100 mm | 500 Hz | General voice work |
| 200 mm | 250 Hz | Voice work in a small hard room |
| 300 mm + | 160 Hz | Only if the low end is the problem |
Two placements that waste material
- Directly behind the microphone, centred. It covers the least useful path and it is the first thing everyone buys. Put panels at the marked mirror points instead.
- Flat in the corners with no air gap. A corner is the right place for a pressure absorber, but a thin panel laid flat against the corner surface is mostly absorbing where the air is not moving.
Do not cover every surface. A room with all reflections removed sounds unnatural and forces the talent to strain to hear themselves. Treat the marked points, leave the rest.
Source log
- 01Refraction of Sound Waves, Penn State Acousticssupports the path behaviour that makes a reflection arrive off-axis
- 02End Corrections for a Pipe, Penn State Acousticssupports the boundary and end-effect behaviour at the edges of an absorber
- 03The Simple Pendulum, Penn State Acousticssupports the oscillator model used to describe a panel's behaviour
Each line points at one specific document. No line is a home page.
Leave this page Close this page once the marked points are covered. Adding more absorption beyond them buys very little.