Can foaming agent in the cat s eye of the entrance door be soundproofed?

This has little to do with the cat's eye, and can even be ignored, the cat's eye will not have much impact on the hole, if the door is not soundproof, you have to check the gap between the door cracks, this is the main thing, and another is the material and quality of the door, thickness, etc.

There is no need to dwell on the cat's eye, which itself is made of two pieces of glass, like a telescope, with an empty middle. The sound will pass through the first layer of glass and it will be weakened by the obstruction of the glass medium, and then the air transmission in the middle will be weakened again, and when the sound passes through the second glass it is already very little, and the structure of the cat's eye itself is soundproof.