Škoda DuoBell: A bicycle bell that outsmarts even smart headphones

Tackling Inattention 

The redesign of a safety feature that is more than 100 years old originated from a simple need. “Bicycle bells have remained almost unchanged for over a century, but the world around them has not. Škoda DuoBell is the first bell ever designed to penetrate noise-cancelling headphones. It is a smart analogue trick that outsmarts the artificial intelligence algorithms in these headphones. It is a small adjustment that will improve safety on city streets,” said Ben Edwards from AMV BBDO, the agency involved in developing the concept. The idea was also supported by the agency PHD, while production company Unit9 contributed to the development of the prototype. 

The number of cyclists in major cities worldwide is increasing. For example, in London, the number of cyclists is expected to surpass the number of car drivers for the first time in history this year. At the same time, however, the risk of collisions between cyclists and inattentive pedestrians is also rising. In 2024 alone, according to data from Transport for London, the number of such incidents increased by 24%.

This trend is partly driven by the growing popularity of headphones equipped with active noise cancellation, which reduce pedestrians’ ability to perceive and respond to their surroundings. In the streets of London, up to half of pedestrians wear such headphones. Many of them are so effective that even the ringing of a conventional bicycle bell does not penetrate them. 

The response is DuoBell: an analogue solution to a digital problem – a fully mechanical bell that deceives smart headphone algorithms and significantly increases the likelihood that pedestrians will detect its sound. 

Scientific Approach 

The key to the success of the new design lay in understanding how noise-cancellation algorithms in headphones operate and how they can be overcome. Scientists from the University of Salford, in collaboration with Škoda Auto, therefore conducted one of the first studies to examine how ANC technology affects the audibility of traditional bicycle bells. 

Through acoustic testing, the research team identified a narrow frequency band – a “safety gap” – capable of penetrating ANC headphone filters. This range lies between 750 and 780 Hz. The bell therefore emits sound at this frequency. It also features an additional resonator (hence the name DuoBell), tuned to a higher frequency, and, thanks to a specially designed hammer mechanism, produces rapid and irregular strikes. This generates sound waves that ANC algorithms are unable to process quickly enough to suppress.