Placed in a high-efficiency sound damping material, not only to absorb sound waves, can also reduce the air molecules spread of the speed of sound, equivalent to the increased volume of the tank, reducing the resonant frequency in the Office of the impedance peak. Another box can also make the air in isothermal compression, so that the effective box volume increase. Music, not just to show the elegant taste, but also a life of Dan Ding, an implication of the quality of life.