Room Mode Calculator
Enter your room dimensions to find all axial, tangential, and oblique resonance modes. Visualize modal distribution up to 300 Hz and get acoustic treatment recommendations.
Room Dimensions
Modal Distribution (0–300 Hz)
💡 Acoustic Treatment Recommendations
Axial Modes List (lowest 20)
| Mode | Frequency (Hz) | Wavelength (m) | Type | Dimension |
|---|---|---|---|---|
| Enter room dimensions above | ||||
Understanding Room Modes
Room modes (also called standing waves or resonances) occur when sound waves reflect between parallel surfaces and reinforce each other. At certain frequencies, a room acts like a resonant cavity, causing some frequencies to be dramatically louder or quieter depending on where you stand.
Types of Room Modes
- Axial modes — occur between two parallel surfaces (one pair of walls, floor/ceiling). These are the strongest and most audible modes. Each dimension produces modes at f = (n × c) / (2L) where n = 1, 2, 3…
- Tangential modes — involve four surfaces (two pairs of walls). They have about 3 dB less energy than axial modes and are often the next most problematic.
- Oblique modes — involve all six surfaces. Weakest of the three types (about 6 dB less than axial), but contribute to the overall modal density.
The Schroeder Frequency
Below the Schroeder frequency (also called the "large room frequency"), the room behaves as a modal resonator — discrete modes dominate. Above it, modes overlap and the statistical approach to room acoustics applies. The Schroeder frequency depends on room volume and reverberation time: fS ≈ 2000 × √(RT60 / V). For typical small rooms with V = 50 m³ and RT60 = 0.4 s, fS ≈ ~283 Hz.
Ideal Room Dimension Ratios
Certain room dimension ratios spread modes more evenly, avoiding "modal clusters" where multiple modes coincide at the same frequency. Well-regarded ratios include:
- EBU (1978) recommendation: 1 : 1.28 : 1.54 (height:width:length)
- Bolt area: ratios in the range of 1 : 1.1–1.45 : 1.4–2.1
- Louden ratios: avoid integer multiples (e.g., 2:3:5 is better than 1:2:4)
- Golden ratio inspired: 1 : 1.618 : 2.618
Avoid ratios where any dimension is a simple multiple of another (e.g., 3m × 6m × 9m) as this causes many modes to coincide.
Acoustic Treatment Strategy
- Bass traps — place in corners where axial modes meet (wall/wall/floor corners have the highest modal pressure). Corner placement is 8× more effective than flat wall placement.
- First reflection points — treat side and ceiling first-reflection points with broadband absorbers for imaging and clarity.
- Rear wall diffusion — diffusers at the rear wall reduce flutter echo while maintaining liveliness.
- Front wall absorption — reduce direct reflections and control flutter between front/rear walls.