Personal Alarm Screech

How it's made

Source

a battery-driven piezo diaphragm, with a 3.2-4.6 kHz carrier rapidly warbled by its driver. A dominant sine, weak second harmonic and still weaker third model the asymmetric diaphragm motion.

Body

a broad 3.9 kHz resonance (Q 1.15), 1.4 kHz high-pass and two low-pass stages model the tiny speaker aperture; no bass cabinet or room tail. Low band-limited air noise sits beneath the tone.

Envelope

continuous alarm, with 6-14 warbles/s and 250-1000 Hz pitch excursion either side of centre. Smooth rounded switching and correlated 18 percent level flutter avoid hard electrical clicks.

Modulation

sine-to-rounded-two-tone warble changes urgency; the fixed diaphragm resonance makes loudness vary naturally as the driver sweeps through it. All preset rates fit whole cycles in 2 s.

Variation

seeded diaphragm tuning varies by +/-0.15 percent; separate seeded aperture noise. Presets offer a piercing keychain, wider sweeping pendant, rapid two-tone, and fabric-covered alarm.

Space

dry mono point source. Fabric cover lowers the aperture cutoff and suppresses upper harmonics.

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