Room mode calculator
A room resonates at frequencies whose half-wavelengths fit its dimensions. Below about 300 Hz that is what you hear, not the speakers.
Lowest room mode
31.18Hz
- First length mode
- 31.18 Hz
- First width mode
- 40.83 Hz
- First height mode
- 65.96 Hz
- Second length mode
- 62.36 Hz
- Second width mode
- 81.67 Hz
- Second height mode
- 131.92 Hz
- Schroeder frequency Below this the room behaves modally; above it, statistically.
- 163.2 Hz
- Length to width ratio
- 1.310
- Width to height ratio
- 1.615
Show the working
- Room length = 5.5
- Room width = 4.2
- Room height = 2.6
- Speed of sound = 343
- First length mode = 343 / (2 * 5.5) = 31.1818
- First width mode = 343 / (2 * 4.2) = 40.8333
- First height mode = 343 / (2 * 2.6) = 65.9615
- Second length mode = 31.1818 * 2 = 62.3636
- Second width mode = 40.8333 * 2 = 81.6667
- Second height mode = 65.9615 * 2 = 131.923
- Lowest room mode = min(31.1818, 40.8333, 65.9615) = 31.1818
- volume = 5.5 * 4.2 * 2.6 = 60.06
- Schroeder frequency = 60.06 > 0 ? 2000 * sqrt(0.4 / 60.06) : 0 = 163.218
- Length to width ratio = 4.2 > 0 ? 5.5/4.2 : 0 = 1.309 52
- Width to height ratio = 2.6 > 0 ? 4.2/2.6 : 0 = 1.615 38
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- axial mode frequency = c / (2 x dimension), and its multiples
- Schroeder frequency is about 2000 sqrt(RT60 / volume)
Dimensions in simple integer ratios stack modes on top of each other and make the problem worse. Avoid cubes.
A mode causes a peak at the walls and a null in the middle. Moving the listening position is free and often more effective than treatment.