Hypnotizing Spirals in the engines,what do they mean?

If you are a frequent flyer ? If yes, then you've probably noticed that most aircraft have swirls(spirals) painted on their engines. And  you might be  wondering what they are for?
so i will explain in this post,they play an important safety measure for ground crew(worker/aircrew) and even for birds.

Use of spirals in engines

We all know that aircraft engines produce large noises when they are running and surely that's enough warning for the ground crew(worker) to be aware of the running engine.

"The spiral plays a straightforward function, alerting ground staff to a running engine and ensuring that no one comes too close to it. If an engine is running, you see a white blur or a hypnotizing swirl, depending on the rotation speed of the engine. This visual cue is extremely clear and warns every ground staff  to stay away from the  jet engines".

"Can’t a ground staff hear the deafening sound of a running jet engine"?

Well, there could be several engines running at once near  to the ground crew, plus they wear hearing protection. If five engines are  running simultaneously ,then it would be like singing in your ears, thus it becomes difficult  task for ground crew to detect an airplane. then by seeing the spiral speed the ground crew are made aware of the particular engine.

Spirals come in different shapes and sizes.The design and size don't actually matter, As they all serve the same purpose which is to warn ground crew if the engine is running.

BE CAREFUL , AND ENJOY YOUR FLIGHT.

EDIT,SUGGESTION,CORRECTION,AND APPRECIATION ARE MOST WELCOMED.

Yours chandra shekar.