Critical distance
Where direct and reverberant sound are equally loud, and matching microphone distances per pattern.
m³
s
1 = omnidirectional source, 2 = on a wall, ≈3–5 = a typical voice or horn.
- Critical distance
- 0.735867m
- …for an omnidirectional source
- 0.735867m
| Pattern | Distance factor | Distance (m) |
|---|---|---|
| Omnidirectional | 1× | 0.736 |
| Wide cardioid | 1.39× | 1.02 |
| Cardioid | 1.73× | 1.27 |
| Supercardioid | 1.93× | 1.42 |
| Hypercardioid | 2× | 1.47 |
| Figure-8 | 1.73× | 1.27 |
How it works
Closer than the critical distance a microphone hears mostly direct sound; farther away it hears mostly room. Directional microphones can be placed farther away for the same direct-to-reverberant ratio, by their distance factor √Q.
The formula assumes a diffuse field, so treat it as a rule of thumb in real rooms.
Formulas
- D_c = 0.057 · √( Q · V / RT60 )
- D_mic = D_c · √Q_mic
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