Cracked Bell

How it's made

Source

a cast bell with a crack struck once by a padded or worn clapper. The strike is a dull 3–6 ms low-passed thud (little energy above 2.5 kHz) plus a faint metallic tick, so the attack never sounds bright.

Body

the partials of a bell (hum 0.5, prime 1, tierce 1.19, quint 1.5, nominal 2, then 2.65, 3.4, 4.3), but the crack splits every partial into two modes a few hertz apart, and the faces of the crack shift the ratios sour (tierce and upper partials pulled 1-3 % out of tune). Split distance grows with `crack`.

Uneven decay

the lower partials ring 2-3 s, while partials whose antinodes lie on the crack are damped and die in 0.2-0.6 s, so the tone changes colour as it fades instead of dying as one smooth spectrum.

Buzz

the two crack faces rub together while the bell vibrates. This is modelled as band-passed noise plus a hard-folded copy of the mid partials, both gated by a 60-130 Hz wandering chatter. It follows the ring level, starts after the strike and fades out earlier than the hum.

Variation

`rng` mistunes partials by up to 0.5 %, varies the chatter rate and the thud, so each render is a slightly different strike; presets move pitch, crack, buzz and ring time.

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