Acoustic foam is a popular item that is easily identified by its distinctive form, which is often that of an egg carton. Why is this unusual form utilised to aid with noise in busy environments? Why not just use foam cushions or something simpler? Before we get into why, let us take a glance at what sound proofing does and does not do.
To begin with, acoustic padding does not suppress sound. Although it is typically linked with soundproofing, acoustic foam is more generally used in conjunction with other materials to produce a noise-free environment. Other components do impede sound, but foam does not. Water waves and ripples are a useful example for understanding how sound proofing works.
Consider a wave striking a flat slab wall inside a body of water; the wave does not just dissipate, but instead bounces off. When you observe this, it’s clear that part, if not the majority, of the waves has been reflected. If you look closely, you will find that the flat and tougher the wall, the greater amount of the wave is reflected back.
Echoes occur in the presence of hard flat roofs for the same reasons that wave reflect off of strong flat walls. While foam does not stop sound, rigid flat surfaces do they simply happen to reflect it? A concrete block will assist block sound from entering the room and keep noises from leaving, while also reflecting them and causing them to reverberate. This is why gymnasiums and cathedrals tend to echo.
That foam is the polar opposite of a solid flat surface. Consider what would happen if a wave collided with an item possessing the physical qualities of acoustic foam. If you like, you may visualise the waves in water again. The wave is not just reflected back. Rather, it is bounces all over and expands out as a result of the bumpy structures in the foam. The wave also is partially absorbed, but more on that in a moment.