Bone conduction headphones use the bones of the head to transmit sound directly to the inner ear. A solution developed for sport but which covers many areas.
Ludwig van Beethoven is a precursor in more ways than one. Having become deaf as he approached his thirties, the German composer had found an alternative to perceive certain sounds he played on the piano. His solution: squeeze a stick between his teeth and hold the other end against the sound box of his instrument.
A technique that allowed him to distinguish the vibrations of the latter via the jaw and thus distinguish the sounds. In reality, Beethoven used the principle of bone conduction.
Nowadays, the latter is experiencing a resurgence of interest from certain manufacturers of headphones and audio headsets, from Tayogo To Creative Labs to Shokz, one of the first companies to develop bone conduction technology.
Hear through the bones
Usually, for a sound to be transmitted to the brain, a sound wave passes through the external auditory canal and causes the eardrum to vibrate. The vibrations of this wave reach the ossicles which send them to the inner ear. This is where the wave is converted into a nerve signal to be transmitted to the brain.
“With bone conduction, sound is transmitted by small vibrations at the level of the temporal bone of the skull to the cochlea, where the inner ear and the auditory nerve that allow hearing are located, and not by air conduction through the eardrum, as is the case with conventional headphones”, explains Xinnan Mao, product manager at Shokz, which markets the OpenRun and OpenRun Pro, two sports headphones that use this technology.
In fact, this device makes it possible to develop open auditory systems that do not require the insertion of earphones in the ears. This makes it possible to clearly hear the surrounding noises (horns, car engine, etc.), thanks to the ears freed from any hindrance, while preserving the perception of sounds emitted by bone conduction.
“This feature improves your safety when doing outdoor activity like sports because you are not isolated. You can clearly see what is happening around you while listening to music,” says Tina Lai, Shokz Marketing Manager France.
Multiple fields of application
“Generally, the design of bone conduction devices allows them to be worn for a long time and comfortably. The fact that the sound is transmitted through the bones preserves the health of your eardrums. It is also more hygienic”, summarizes Tina Lai.
In addition, bone conduction works perfectly underwater, because sound waves do not pass through the air. It can also be a credible alternative for people who suffer from hearing impairment.
“We faced two challenges related to this technology for the design of our headphones: to make sure to optimize the sound quality so that it comes as close as possible to a closed device. Second, to work on sound leakage which escape from the headphones to ensure that only the user enjoys their music”, summarizes Xinnan Mao.
Apart from entertainment, the nature of this technology allows it to be applied to different use cases. In particular professionals: some companies, Carrefour or Renault, have it used by their employees who work in the factory by providing them with bone conduction helmets. This allows them to communicate while remaining vigilant to the noises of the machines, sometimes dangerous, which surround them.
A technology that still needs to evolve
While bone conduction has practical advantages and has improved in recent years, it still has room for improvement. “Improvements can still be made to the sound quality”, which still suffers from the comparison with that developed by a helmet where the ears are isolated recognizes Xinnan Mao.
The latter evokes as avenues for progress the arrival of noise reduction functions in future headphones, as well as functions intended to improve the level of bass and restrict sound leakage.
“Especially for sports, bone conduction headphones are excellent complementary products for owners of closed models,” says Tina Lai.
