Dec [{(
)}]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
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.
Geert Uytterhoeven