When looking at real-time ultrasound images, the primary movement you would notice in the heart would be the opening and closing of the valves that connect heart chambers. You would also see the squeezing motion of the heart muscles.

A special type of ultrasound called doppler ultrasound can see the movement of the blood flow into and out of the heart, with blood displayed as blue or red depending on the direction of flow. The “sound” of the heartbeat of a fetus is actually an audible whooshing sound created by the machine from doppler ultrasound data.