Doppler effect

Due to the Doppler effect, a fire truck's siren gets higher-pitched as it travels closer and sounds lower-pitched as it drives farther away.

Keck Observatory on Hawaii's Mauna Kea, they could detect slight variations in stellar motion via the redshift and blueshift of the Doppler effect -- which helped them determine planetary mass readings of unprecedented precision.

In contrast, ultrasound imaging, considered safe enough for fetal monitoring, utilizes the Doppler effect to measure real-time blood flow velocity and direction without the need for contrast agents.

Their speeds would be carefully calibrated to create different layers of the Doppler effect, or the bending in a note that we perceive when sound passes us by.

Sometimes I go to sleep to the bizarre Doppler effect of planes that sound as if they’re about to crash into my house.