Why does it crackle when we take off our sweater?

When you take off your sweater, you will hear a crackling sound because there is a small thunder.
The crackling sound of the sweater and the thunder are the work of static electricity that can be created by rubbing objects.
What exactly is static electricity?

Static electricity is the electricity generated when things are rubbed together.
Everything, such as a sweater, our body, always has the same number of plus and minus grains of electricity.
However, if you rub different materials together, the negative particles may move to one of the materials. The material with more negative grains is charged with negative electricity, and the material with less negative grains is charged with positive electricity.
When static electricity is generated, the hair sticks to the sweater because the positives and the negatives attract each other.
When the plus and minus approach, the minus grain tries to return and moves towards the plus. This is the flow of electricity.
When you touch the handle of the door, you will feel tingling because electricity is flowing.

So why does it make a noise when static electricity is generated?
When a lot of negative particles are accumulated, the power to flow electricity becomes stronger. Then, a narrow passage is created in the air that should not conduct electricity, and negative particles may forcibly pop out.
When a negative grain pops out, the path becomes hotter than 1000 degrees for a moment.
Then, the air around the path suddenly swells due to the heat, and a tremor is created, and it is transmitted to the outside more and more.
This trembling of the air is transmitted to our ears and can be heard as a crackling sound.
When lightning strikes nearby, you will hear a short crackling sound like a boss of a sweater's crackling sound.
The reason why distant thunder can be heard for a long time is that the tremors of the air bounce off various places while being transmitted from a distance.
When the path of negative grains becomes hot, light also comes out.
This is lightning.
If you take off your sweater in the dark, you may see a small light.
The lightning of thunder and the small light that you see when you take off your sweater are phenomena in which the path through which electricity flows shines.