【摘要】 采用描述波源运动、观察者运动及声波在静止空气中以声速传播的三组时空线，用几何方法导出多普勒公式，并通过时空线相交分析多普勒效应中观察者接收声波信号的时序及周期，着重讨论一般文献中未曾涉及的不同条件下多普勒效应的结果及其物理意义．更多还原

【Abstract】 Three searies of time-space lines are proposed, which represent the motion of sound source, motion of observer and sound propogation in static air respectively. The Doppler formula is deduced by means of geometric methods.更多还原