Czech carmaker Škoda recently worked on a road safety project, but this time for bicycles instead of cars. A team at the company, along with hearing experts from the University of Salford in the UK, has found a way to keep cyclists from hitting pedestrians who are wearing noise-canceling headphones. Their solution is a better bicycle bell.
Noise-canceling headphones work by picking up the sounds around you with small microphones. They then play an opposite sound to cancel that noise out.
Focusing on busy London traffic, the researchers tested hundreds of sounds on a number of popular noise-canceling headphones, including both over-ear and in-ear models from several leading brands. They found a weak point: the headphones were less effective at blocking a narrow band of sounds between 750 and 780 Hz. The next step was to make a bell that could hit this range, so that people wearing these headphones could still hear it from a distance.
The bell is completely mechanical. Its secret lies in careful design and precise production, and it took a lot of engineering to produce that sound while keeping the bell about the same size as a normal bike bell.
The bell is called the DuoBell because it has a second feature. Another part of the bell is tuned to a higher pitch. It makes quick, irregular strikes, and the headphones cannot process them fast enough to stop them from reaching your ears.
In a virtual reality test, people walked through computer-made streets. The bell reportedly gave them about 22 meters, or 5 seconds, of extra warning. That extra time allows pedestrians to react and step out of the way of oncoming bicycles. The bell was also tested on real London streets by delivery riders.
The company isn't selling the bell yet, but it has made its research findings freely available.