TL;DR
- Skoda has developed the Duobell, a mechanical bicycle bell specially designed to be heard through noise-canceling headphones.
- The research identified a frequency “gap” between 750Hz and 780Hz where ANC algorithms are least effective at suppressing external noise.
- The bell also uses a dual resonator system and an irregular striking mechanism, which helps prevent the ANC algorithms from processing and blocking the sound.
Active noise cancellation (ANC) on headphones and earphones has gotten really good. As more and more users upgrade to new products with more effective ANC, the second-order effect is increasing: people are becoming inattentive, especially when walking on the road, increasing their chances of colliding with cyclists whose mechanical bells are no longer effective. Czech carmaker Skoda (which started out manufacturing bicycles) is tackling the ANC threat with the new Skoda DuoBell, the first bicycle bell designed to circumvent ANC on headphones.
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The Skoda Duobell is a completely mechanical bell that tricks ANC algorithms and significantly increases the chance that pedestrians will detect its sound.
Through acoustic testing, Skoda and a group of scientists from the University of Salford identified a narrow frequency band between 750 Hz and 780 Hz where ANC is least effective. Duobell can emit sound at this frequency.
To further enhance its efficacy, the Duobell also has an additional resonator tuned to a higher frequency. It also has a specially designed hammer mechanism that delivers rapid, irregular blows. Combined, the Duobell produces sound waves that the ANC algorithm cannot process fast enough to suppress.
Given the ever-increasing popularity of ANC headphones and earphones, such simple, mechanical gadgets are the need of the hour. However, it wouldn’t be surprising if audio companies further improve their ANC to try and close the safety gap. For the safety of everyone involved, I hope the entire industry will come together to agree and maintain such “safety gaps” to protect all consumers.
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