节拍器可分为机械式、电动式和电子式三种,其中机械式节拍器的工作原理是利用发条旋紧,储存的机械能慢慢释放作为动力维持节拍器发出周期性的声音;二胡、管乐乐器都是满足____条件,发出悦耳的声音。 Metronomes can be divided into mechanical, electric and electronic types. The working principle of mechanical metronomes is to use a spring to tighten, and the stored mechanical energy is slowly released as the power to keep the metronome periodic sound. Erhu and wind instruments were both served to provide a pleasant sound.
A.驻波 Standing Wave;
B.行波 Travelling Waves;
C.横波,行波 Shear Wave, Travelling Waves;
D.纵波 Longitudinal Wave;