Sound insulation pressure class A of the enclosure

How effectively a wall "stops" sounds and prevents them from traveling further.

In the chaos of the sounds surrounding us – the rustle of the wind, the buzz of the street, or the cracks – our brain has an extraordinary ability to catch order. It is this order that makes us perceive some sounds as "musical," pure, and pleasant, while others are perceived as formless noise. The key to this harmony is repetitiveness, which is a feature that defines periodic sound.

What happens at the moment the wave collides with the wall determines whether we hear an echo or silence.