Acoustic Room Mode Calculator
Calculate the first three axial room mode resonance frequencies for length, width, and height dimensions. Essential for home studio design and bass trap placement.
Results
What is it?
Axial room modes are standing waves that form between pairs of parallel walls when the room length (or width or height) equals a whole number multiple of half wavelengths. These modes cause dramatic frequency response peaks and nulls � you might hear too much or too little bass depending on where you stand. They are the primary acoustic problem in small studios and home theaters.
How to use
Enter your room's three dimensions in meters. The calculator shows the first three axial mode frequencies for each dimension. Look for modes that cluster closely together (within 5 Hz) � these "modal pile-ups" create severe problems. Ideal ratios avoid coincident modes (e.g., Sepmeyer ratios: 1:1.14:1.39 or 1:1.28:1.54).
Example scenario
A 5m � 3.5m � 2.7m room has: Length modes at 34.3, 68.6, 102.9 Hz; Width modes at 49.0, 98.0, 147.0 Hz; Height modes at 63.5, 127.0, 190.5 Hz. The 98�102 Hz range has two modes within 5 Hz � a modal pile-up. Place broadband bass traps (4-inch rockwool) in all four vertical corners and both floor-ceiling corners.
Pro tip
The Schroeder frequency marks where individual modes become too dense to distinguish and room behaviour transitions to diffuse. Below Schroeder frequency, modes dominate. A rough estimate: Schroeder � 2000 � sqrt(RT60/V) where V is room volume and RT60 is reverberation time. For a 47 m� room with RT60=0.4s, Schroeder � 179 Hz � treat everything below this with absorption.