“Every single day, I see at least five or six people with headphones on while cycling,” says Gemma Roper. The designer and recent graduate of London's Royal College of Art finds the habit a troubling distraction but also an understandable tactic of using music to soften a harsh daily commute.

The problem is that cyclists also need to stay alert to certain sounds in order to be safe while weaving through traffic. Riding is already dicey in London, Roper says, because the local infrastructure accommodates bus and car traffic over cyclists. The city has seen eight cyclist fatalities so far this year; last year, there were 13. Roper decided that music pumping through earphones shouldn't contribute to the risk. Her Safe + Sound headphone design uses bone conduction to play tunes through wearers' cheekbones, instead of directly into their eardrums, so they can still detect ambient noise.

Gemma Roper

Bone-conduction headphones work by playing soundwave vibrations on top of bones, which then transmit the waves into to the Cochlea, or inner ear, bypassing the delicate eardrum. It could work anywhere on the body but works best near the ear.The technique itself is old—Beethoven, who was deaf, crafted a crude conductive listening device by biting on a metal rod attached to his piano—and a few other headphone makers have rolled out models using the technology in recent years.

Roper’s Safe + Sound are made with cycling helmets in mind. Most of the bone-conduction headphones on the market are wrap around the ear (like these, and these), with nodes that rest more or less where a helmet strap would sit. Asking cyclists to layer up headgear is an uncomfortable and unreasonable ask. At the same time, making any modifications to the helmet that might deter a rider from wearing one is out of the question. So Roper created something that could clip onto to a helmet's straps. While testing out the idea, she also found that asking cyclists to tote around two pairs of headphones will slow down adoption, so her buds convert into a regular pair of headphones; the modular bone-conducting pieces fit magnetically into a pair of gold muffs.

London has yet to pass a ban on wearing headphones while riding a bike, and only five states in the U.S. forbid the practice. For now, Roper's design, a working prototype, could be the transitional object cyclists need before giving up their headphones cold turkey.