Alarm Bell Loop

How it's made

Source

an electric alarm bell. A solenoid drives a clapper back and forth against a steel gong shell, 12-28 times per second, so the excitation is a fast, slightly irregular train of 1-3 ms metallic clicks whose timing wobbles with the magnet's supply ripple and the clapper's bounce.

Body

the shell rings in inharmonic steel modes, ratios 1 : 1.52 : 2.35 : 3.1 : 4.2 : 5.6 : 7.3, with a 0.4-1.6 s decay. Closely spaced mode pairs beat slowly. Each ring has not died before the next strike, so the modes pile up into a dense, harsh, constant-level ring with a rattle on top.

Envelope

no overall envelope; the level is constant. The clapper clicks add a bright, dry 3-8 kHz rattle layer and a small thump from the gong mount at the strike rate.

Space

a slight room echo, two quiet early reflections at 38 ms and 71 ms plus a damped comb at 113 ms.

Loop

4 s; the strike train is statistically stationary, so the crossfade seam is inaudible.

Variation

`rng` mistunes the modes by up to 0.5 % and jitters the strike timing; presets change the shell size, strike rate, harshness and echo.

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