Abstract: The technology is specially designed for headphone to allow the listener to distinguish the direction and the distance from a sound source, just as if the listener is in a natural environment. The technology relies on optimizing the three factors that human being uses to distinguish sound source location and sound source distance. They are relative loudness, relative pitch and relative reverberation. The technology makes use of the specially-designed sound box with specific construction and specific materials to re-create the 3D hearing feeling. The specially-designed sound box generates appropriate amount of reflection, reverberation and interference at different frequency range, which optimize the three principal factors.

Abstract: The present invention relates to a constant mesh clutch for transmission of rotational movement between an input and an output, comprising a first sun gear and a second sun gear, a number of planet gears in mesh with said sun gears and held in a carrier, wherein said carrier has a disc formed integral with it and extending radially for a caliper fixed on the flywheel house to apply a braking force upon it; and said second sun gear has a shaft formed integral with it and serving to carry said first sun gear. As a different braking force is applied on said disc, the power transmitted from said first sun gear through said planet gears to said second sun gear also changes, thus realizing a stepless transmission of power between an input and an output. The constant mesh clutch of the present invention is not only simple in structure and easy to maintain, but also has a high efficiency.