DuoBell tunes a bicycle bell to outsmart noise-cancelling headphones
Škoda's DuoBell is a passive bicycle bell tuned to 750 Hz with a sharp transient attack to break through active noise cancellation, plus a high-frequency component to preserve the bell's sound; in tests, ANC headphones reduced detection distance for normal bells, but the 750 Hz tone improved it by about 9.2 meters and lowered the detection threshold by 2.3 dB in noisy settings, and the device has no electronics—an analogue fix to a digital problem that raises questions about future liability as ANC tech evolves.
