Dec [{()}]1d ago

Skoda developed (with the University of Salford) an all-mechanical bicycle bell that bypasses active noise cancellation (ANC) in headphones.
https://www.skoda-storyboard.com/en/skoda-world/skoda-duobell-a-bicycle-bell-that-outsmarts-even-smart-headphones/
It's tuned to 750hz, which is a "blind spot" in most ANC headphone processing.
There is also a resonator for a higher frequency, and the hammer produces irregular strikes, confusing the ANC further, and making pedestrians look behind them faster.

Video:
https://www.youtube.com/watch?v=zDaVPfpQvPI

Research:
https://cdn.skoda-storyboard.com/2026/04/Skoda-DuoBell-Research-final_cf127752.pdf

#BikeTooter

Škoda DuoBell: A bicycle bell that outsmarts even smart headphones - Škoda Storyboard

Pedestrians wearing headphones are exposed to an increased risk of accidents. In an effort to reduce collisions with cyclists, Škoda Auto, in collaboration with scientists, introduces an innovative bicycle bell whose sound can penetrate even active noise cancellation systems. In doing so, it helps prevent injuries to both pedestrians and cyclists.

Škoda Storyboard
Show threadDźwiedziu
@dec23k
750Hz seems weird, as there is no one emergency signal frequency, yet better than my idea of blasting directional infrasounds, to make pedestrians viscerally afraid of crossing cyclists' paths ^_^
6:36amFedilab
Show threadDec [{()}]12h ago

@dzwiedziu
That 750Hz could be an artifact of the DSP in the headphone design, or even something as simple as the casing around the microphone causing a notch filter (not as dramatic as what they show in the video). I would expect it to be different across different manufacturers.

If 770Hz is close enough, then playing the DTMF for 666 loud over a Bluetooth speaker should also work!