A method for dynamically controlling audio signal gain in a communication device starts with determining a level of an input audio signal. The floral holding material is a preformed shape-sustaining support member, which is selectively movable between an expanded condition and a flattened condition, is provided with a stabilizing assembly for stabilizing the preformed shape-sustaining support member in the expanded condition. The rotational speed of the rotation axis is detected. This invention respectively adjusts the brightness of the backlight source and the voltage of the pixel capacitor of the liquid crystal panel simultaneously, and hence the dynamic contrast of the picture is increased, the problems of lower contrast and flicker of TFT liquid crystal display apparatus are ameliorated, and the power consumption of the backlight source is saved.