Music · Room acoustics
Room mode calculator.
Enter your room dimensions to list the lowest standing-wave frequencies, so you can see where bass will build up in a studio, practice room or listening room.
Your numbers
Resonances
Fill the form to see the result.
How do you calculate room modes?
For a rectangular room with rigid walls the natural frequencies are f = (c / 2) × √((l/L)² + (m/W)² + (n/H)²), where c is the speed of sound, L, W and H are the room dimensions and l, m, n are whole numbers (not all zero). Modes with one non-zero index are axial, two are tangential and three are oblique. Axial modes generally carry the most energy and have the greatest influence on the low-frequency response. Most rooms have their fundamental resonances in the 20 to 200 Hz region.
Worked example. A 5 × 4 × 2.5 m room at 20 °C, where the speed of sound is c ≈ 331.32 + 0.606 × 20 = 343.44 m/s. The first axial modes are 34.3 Hz (length), 42.9 Hz (width) and 68.7 Hz (height). With RT60 = 0.5 s and a volume of 50 m³ the Schroeder frequency is 2000 × √(0.5 / 50) = 200 Hz.
What the Schroeder frequency means. Discrete room modes dominate only at low frequencies. Above the Schroeder frequency the modes overlap so densely that the room response is better treated statistically. The formula is a commonly used approximation.
Limits. The calculator assumes a perfect rectangular box with rigid walls. Real rooms have soft walls, doors, furniture and non-parallel surfaces, so treat the list as a guide to where problems are likely, not a measurement. Measure the room with a microphone for treatment decisions.
Frequently asked questions
What is a room mode?
A resonance of the air in a room, where sound waves reflect between surfaces and form standing waves at certain frequencies, mostly in the 20 to 200 Hz region.
What is the formula for the axial mode frequency?
f = c x n / (2 x L) for a dimension L. The first axial mode of a 5 m dimension at c = 343.4 m/s is 34.3 Hz.
What speed of sound does the calculator use?
About 343 m/s at 20 °C, from c = 331.32 + 0.606 x temperature in °C. It rises with warmer air.
What is the Schroeder frequency?
The transition above which modes overlap so densely that the room is treated statistically, approximated as 2000 x sqrt(RT60 / volume in m3).
How do I fix a bad room mode?
This tool only finds likely problem frequencies. Fixes such as bass traps and speaker or listener position are best decided by measuring the room.
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