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
@dec23k @jwildeboer This looks very much like our old GDR bike bells. The exact same mechanics inside 😂
@maxheadroom No surprises here, knowing the history of Skoda :) And by making the research available, I expect Anti-ANC bike bells flooding the market really soon :) @dec23k

@jwildeboer
I expect anti-anti ANC bell headphones flooding the market soon enough, too.

@maxheadroom @dec23k

@datenhalde @jwildeboer @maxheadroom
The website says the "hammer mechanism produces rapid and irregular strikes".

So the extra processing power needed to decode the random timing will drain the batteries in the new headphones faster.