“Whisper” is a new wrist-worn handset, which is used by inserting the fingertip into the ear canal. A received signal is conveyed from a wrist-mounted actuator to the ear canal via the hand and a finger by bone conduction. The user’s voice is captured by a microphone mounted on the inside of the wrist. All components of Whisper can be mounted on the wrist, and usability does not decrease if the size of components is miniaturized. So, both wearability and usability can be achieved together. The way Whisper is operated is similar to that of an ordinary telephone handset. Thus, onlookers may not look upon Whisper’s operation as “talking to oneself”, even if the associated PDA is controlled by voice commands. Whisper is especially effective in a noisy environment. Signals received via bone conduction can be heard clearly in the presence of noise without raising the volume (-12 dB at noise = 90 dB(A) in comparison to cellular phone handset). Whisper is also effective in avoidin...