The effects of periodic source micromotion on an acoustic signal are examined with micromotion in the vertical plane being emphasized. Single phone radial and skew source motions are investigated utilizing cw and narrow‐band equispaced, equal amplitude, multitonal signals of 200 ±1/2 Hz. Brief comments on array reception are included. The study shows that source micromotion does not appreciably affect the coherence bandwidth of the received signal, but introduces a fluctuation having the period of the micromotion,Tmm, which can reduce coherence times appreciably. Spatial coherence lengths are extremely large due to the simplified ray model. Micromotion transfers power from the central peak of the power spectrum to side bands separated from that central peak by ±1/TmmHz. The power in the spectral side band of the received signal is dependent on the signal level and the magnitude of the source micromotion.