Street Canyon Noise (2D)

Cross-section level map of a street between two facades, with image-source reflections, a noise wall and indoor level behind glazing.

Switch to 3D

Presets

Playback

Traffic

Flow, share of trucks and speed set the source power.

Street

Geometry and absorption set the build-up.

Receiver

Click the map or use the sliders.

Layers

Model checks

The science

Line sources and image sources

Each carriageway is an incoherent line source. A vehicle of sound power level LW adds, per metre of road, LW' = LW + 10 lg(Q / (3600 v)). Over hard ground a line source gives

Lp = LW' − 10 lg(2 r) − Aair

Two parallel facades act as mirrors: the energy of each image line at distance rn is multiplied by (1 − α)n after n bounces. The page sums the energies of 26 image columns, discards rays that would pass over the roof line, and adds Maekawa diffraction loss A = 10 lg(3 + 20 N) for a noise wall.

Windows

Indoors: Lin = Lout − Rw + 10 lg(S/A) + 3 with S = 2 m2 window and A = 10 m2 room absorption.

Honest simplifications

  • Cross-section (2D) energy model; no wind, temperature gradients, turbulence or coherence between images.
  • Single-frequency (about 500 Hz) barrier loss and a flat 1 kHz air absorption; real regulations use spectra.
  • Vehicle sound power is a CNOSSOS-like fit, not a calibrated database.
  • Cars are drawn end-on for illustration only.
What to try
  • Load Narrow canyon then Same canyon, absorptive walls and watch the level map cool by several dB.
  • Raise the noise wall: the receiver at 1.5 m is shielded, the one at 8 m is not.
  • Double the flow: exactly +3 dB. Make 25 % of vehicles trucks: the energy sum is dominated by them.
  • Click the map to drag the receiver to the window and compare glazing types against the 30 dB night guideline.
Level against height at the receiver column
Level across the street at receiver height
Level against traffic flow (3 dB per doubling)
Level against facade absorption