Mastodawn

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

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Slash909uk 1d ago

@dec23k interesting.

From the paper I understand the 750Hz tone is around 3dB less attenuated, but only in quiet areas with already not much noise, like parks.

In noisy areas, any tone that is distinct from the noise is more easily heard. But everything is attenuated and the warning distance is considerably lower already.

I wonder if these ANC headphone makers are obliged to support 'emergency' vehicle tone detection and not blank it out? Does anyone know?

Or there is the air horn solution🤪

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Dźwiedziu 13h ago

@Slash909uk
> I wonder if these ANC headphone makers are obliged to support 'emergency' vehicle tone detection and not blank it out?

I would assume so, because of the potential legal liability.
Yet 750Hz meets this only partially, as it's the lower range of the lower band of the UK's and few other European countries two-tone pattern¹.

So that would assume there are more frequencies to take into account and wanted to check in with RTINGS tests, but they »

@dzwiedziu @Slash909uk
Regular DTMF tones are close - the numbers 4 5 6 include 770hz.

May or may not be close enough.
I don't have any ANC headphones so I can't test that myself.