Answer
This is not exactly the same as your examples… Especially the first one, but maybe it’s close enough.
- Start with a white rectangle
Effect > Artistic > Sponge...
- Definition and smoothness should be quite high.
Object Expand Appearance
so that you can trace it.Object > Image Trace > Make...
- Use
black & white
preset as the starting point. - Adjust the threshold and other sliders if needed.
- Check
Ignore White
- Expand it
- Use
Attribution
Source : Link , Question Author : Eugene , Answer Author : Joonas