Room Mode Calculator

Room size

Uses the speed of sound at room temperature: 1,125 ft/s (343 m/s). Axial modes only, which are usually the strongest.

Room modes from 20 to 300 Hz

Length Width Height

All axial modes

OrderLengthWidthHeight

What to do with the result

  • Modes that land close together build up into a boomy or muddy note, often in the corners and along the walls.
  • Low room modes are bass problems. They are treated with thick bass traps in the corners, not thin wall panels.
  • Thin felt panels like ours work on the mid and high frequencies: echo, flutter between parallel walls, and the hollow sound on calls and recordings.
  • Sit and place speakers away from the exact middle of the room and away from walls; small moves change how strongly you hear each mode.

Work out how many panels you need

 

What room modes are

Every room has a set of bass notes that it naturally reinforces. They happen when a sound wave fits exactly between two parallel surfaces: the two end walls, the two side walls, or the floor and ceiling. At those frequencies, called room modes or standing waves, the bass gets louder in some places and almost disappears in others.

How the calculator works

It calculates the axial modes for each dimension: frequency = order x speed of sound / (2 x dimension). With the speed of sound at 1,125 ft/s, a 14 ft room has its first length mode at about 40 Hz, the second at about 80 Hz, and so on. Axial modes are usually the strongest, so they are the ones to check first.

When modes from different dimensions land within about 5% of each other, they stack and that note can sound noticeably boomy. Rooms where two dimensions are the same, or one is double the other, tend to stack the most.

What to do about room modes

  • Move your listening position and speakers away from the exact centre of the room and away from walls.
  • Use bass traps, which are thick absorbers placed in corners. Thin panels do not reach down to bass frequencies.
  • Treat echo separately. Felt panels handle mid and high frequencies, where voices and flutter echo live. Use the panel calculator to size those.

This calculator gives a quick estimate. Real rooms with open doorways, sloped ceilings or unusual shapes behave differently.