Room Mode Frequency Calculator
Find the axial room modes — the standing-wave frequencies where bass builds up or cancels — from your room length, width and height.
How it works
f = (n · c) ÷ (2 · L), c = 343 m/s, n = 1, 2, 3…
Between any pair of parallel walls, sound waves whose half-wavelength divides evenly into the distance reinforce themselves into standing waves called axial modes. At a mode frequency the bass piles up in some spots and cancels in others, which is why one seat sounds boomy and another sounds thin. Evenly spaced modes are the goal; when two dimensions share a mode, that frequency is doubly excited and problems worsen.
Worked example
A 6 m long room has its first length mode at 343 ÷ (2 × 6) = 28.6 Hz, with further modes at 57.2, 85.8 and 114.4 Hz. A 2.7 m ceiling puts its first mode at 63.5 Hz — close to the third length mode, so around 60 Hz two modes overlap.
Frequently asked questions
What are tangential and oblique modes?
Axial modes involve one pair of walls and are the strongest. Tangential modes bounce off four surfaces and oblique modes off all six; they are weaker (about 3 dB and 6 dB lower) but more numerous. This calculator shows the dominant axial modes, which cause most audible bass problems.
How do I fix a bad room mode?
You cannot remove modes, but you can tame them: bass traps in the corners absorb low-frequency energy, moving the listening position and subwoofer changes which modes you sit in, and multiple subs can smooth the response. Room dimensions with a good ratio (avoiding whole-number multiples) spread the modes more evenly.
Why does the height matter as much as length?
Every parallel surface pair creates modes, including floor and ceiling. A common 2.7 m ceiling puts a mode near 63 Hz — right in the kick-drum and bass-guitar range — so ceiling modes are often just as audible as those between the walls.
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This calculator is for educational purposes. Double-check important results before acting on them.