It's a physics phenomenon called the Doppler effect. Named after Christian Doppler who first described it. https://en.m.wikipedia.org/wiki/Doppler_effect

What you’re noticing is called the Doppler effect. It’s all about how sound waves behave when the object making the sound is moving. When a sound source (like a car honking its horn) moves toward you, the sound waves in front of it get squished together. This makes the waves hit your ears more frequently, which makes the sound seem higher-pitched. As the car moves away, the waves stretch out, so they hit your ears less and sound lower in frequency.

Hot take: this is also why the Sunrise, and associated color change in the sky, appear to occur more quickly than the same effects of the sunset. My personal observation.

The Doppler Effect. Sound pitch increases as it moves towards you, and decreases as it moves away. It’s not just sound that works this way, but light too. It changes color due to motion, shifting to either blue or red, depending on whether it’s proceding or receding. It’s one method used in astronomy to guage the expansion of the universe.

It’s arriving at your ears more quickly, which is shortening the wave...

Objects, like people, get excited when they’re approaching someone. This excitement causes the molecules in the air to vibrate faster, raising the pitch of the sound. As they pass, they recognize you, become disappointed, calm down, and the pitch lowers. (This is not true. For the actual answer, read my next post.)

Doppler effect.

Electrical gremlins