People wearing headphones using active noise cancellation (ANC) are often left in a perceptive bubble where they fail to react — or simply react too late — to imminent dangers they can’t hear coming. Now, the Czech brand Škoda DuoBell bicycle bell is a solution to that problem. Researchers at the company have figured out how to make the bell’s ringing sound bypass the ANC capabilities of modern headphones. Something they call the “safety gap” — which is located in the frequency range between 750 and 780 Hz — can reach the ears of people using noise-cancelling headphones. The structure of the bell is completely mechanical, but it also includes an additional resonator tuned to a higher frequency to improve the bell’s overall efficiency. The hammer mechanism also generates rapid blows. This is ideal for city environments when more than one ding is often necessary to get someone's attention, but it's also integral to the design because the rapid, irregular dings are harder for ANC systems to cancel out. There’s currently no information about pricing or availability, but when released it’s likely to become a powerful new early warning device.
