The phone went on sale Thursday in Japan through au, the country's second-largest carrier. Kyocera says it is the world's first to use "tissue conduction" technology in this way. The vibrations produced by the phone are picked by the ear physically, meaning there is less interference from background noise.

(See of the phone on YouTube.)

The company is displaying the phone at the Wireless Japan exhibition in Tokyo. It is easy to use, but requires that the phone be firmly pressed against the side of the user's face. To demonstrate its benefit in a noisy background, exhibition visitors can use the phone in front of a speaker that blasts out construction and other background noise. Conversations using the phone are clearly audible above the ruckus.

The phone uses a device it calls its "Smart Sonic Receiver," which is under the top half of the phone's screen, to produce the vibrations. It also works through headphones or other headwear that is pressed against the ear.

Japanese manufacturers like Kyocera, initially caught off guard by the sudden popularity in smartphones, are increasingly rolling out models with quirky technologies to distinguish themselves. Apple's iPhone, now carried by two of the big three mobile operators in the country, remains the dominant smartphone, although Japanese makers also retain a strong presence.