Room Simulator

#Audio#Acoustics#Simulation

Most room mode calculators give you a table of frequencies and call it a day. That’s useful for a rectangular box, but real rooms can have alcoves, angled walls, and non-parallel surfaces. And a list of mode frequencies tells you nothing about what the response actually looks like at a specific listening position.

This tool does both. Analytical mode calculation for rectangular rooms and a 2D finite element solver for arbitrary shapes. For any room geometry, you get the frequency response at the listener position with full source interaction: phase, delay, gain, polarity.

What It Does

  • Rectangular rooms: closed-form mode computation (axial, tangential, oblique) with mode distribution and Bonello analysis
  • Custom room shapes: draw any floor plan polygon and compute modes via 2D FEM eigenvalue analysis
  • Frequency response: transfer function at the listener position accounting for all sources, with 1/12 and 1/3 octave smoothing
  • Pressure mapping: heatmap overlay showing SPL distribution across the room at any frequency
  • Mode shapes: visualize individual eigenmode patterns
  • Multiple sources: up to 6 subwoofers with independent gain, delay, and polarity

Why Arbitrary Shapes Matter

Rectangular mode formulas assume rigid, perfectly parallel walls. That works for some rooms, but many real spaces don’t fit the model. Home theaters with bump-outs, studios with splayed walls, L-shaped rooms. The FEM solver handles any 2D geometry by meshing the floor plan and solving the Helmholtz equation directly. The tradeoff is computation time, but it runs fast enough for interactive use in a browser.

Source Placement

Where you put the subwoofer matters as much as which room modes exist. A mode that’s 15 dB at one position might be barely excited at another. The pressure heatmap lets you sweep frequency and see where the hot spots and nulls are, then move sources to find positions that give the most even response at the listening position.

With multiple sources, you can experiment with delay and polarity to cancel specific modes or fill nulls. The frequency response updates in real time as you drag sources around.

Limitations

The model assumes rigid boundaries with uniform absorption. Real walls have frequency-dependent absorption and finite impedance. The 2D FEM solver computes horizontal modes only and combines them with vertical axial modes, so it doesn’t capture full 3D oblique modes in non-rectangular rooms. Furniture, treatment, and diffusion are not modeled.

Use this to understand modal behavior and find good starting positions for sources and listeners. Verify with measurement.

Try It

Room Simulator - runs in browser, no installation.