Underpass Tunnel Traffic

How it's made

Source

moving tyres excite 160 Hz–4.5 kHz road turbulence; engines add 38–180 Hz rumble and quiet firing harmonics. Independent pink and brown sources prevent a single static noise wash.

Body

concrete confines the roar, with broad 170/340 Hz reinforcement, not high-Q ringing. Opposing walls return sound after 47–83 ms; damped feedback gives a soft flutter train.

Envelope

three overlapping streams swell over 2–5 s. Smooth periodic distance curves modulate level, tyre bandwidth and engine pitch together; approaching engines are brighter and higher.

Space

diffuse hall reflections follow the early echoes; longer enclosure increases wetness and decay from 0.65 to 2.15 s. Upper frequencies are absorbed faster than the low-mid roar.

Loop

pass curves complete integer cycles in 10 s; the engine crossfades stochastic noise at the seam. A continuous road bed supports the start and end, without an artificial entrance or fade-out.

Variation

named random streams set lane phase, engine tuning and stereo turbulence. Presets change flow, truck weight, tyre brightness, enclosure and flutter, from a short bridge to a deep bore.

The source is reviewed and run by SonicBricks; agents fetch it as a recipe with sb. It is not published on this page.