Acoustical treatment materials can be roughly divided into sound absorption materials, diffusion materials and sound insulation materials according to their functions.

Acoustical treatment materials can be roughly divided into sound absorption materials, diffusion materials and sound insulation materials according to their functions. Among them, the sound-absorbing material is not only the conventional sound-absorbing plate, but also the low-frequency trap which is usually used to absorb low frequencies. First of all, we need to know how the sound will continue to spread after it has spread to our common walls.

Acoustical treatment materials (1)
Acoustical treatment materials (2)

Incident sound-reflected sound = sound absorption coefficient

Incident sound-transmitted sound = transmission loss

Some of the sound is absorbed by the wall and turned into heat energy.

From the above relationship, it is not difficult to find that sound insulation can only ensure as little transmitted sound as possible, but it does not necessarily have a good sound absorption effect.

sound absorbing material
Traditional sound-absorbing materials are porous materials, or the scientific name is acoustic resistance sound-absorbing materials. The essence of sound wave is a kind of vibration, exactly speaking, it is air vibration for the speaker system. When air vibration is transmitted to this sound-absorbing material, it will be gradually relieved by the fine pore structure and converted into heat energy.

Generally speaking, the thicker the sound-absorbing material is, the more such small holes are in the direction of sound propagation, and the better the absorption effect of sound incident immediately or at a small angle is.

Diffusion material

Acoustical treatment materials (3)

When the sound is incident on the wall, some sound will exit along the geometric direction and continue to spread, but usually this process is not an absolute "specular reflection". If it is an ideal absolute reflection, the sound should exit completely in the geometric direction after passing through the surface, and the energy in the exit direction is consistent with the incident direction. The whole process does not lose energy, which can be understood as no diffusion at all, or more popularly as specular reflection in optics.

sound insulating material
The sound insulation and sound absorption properties of materials are different. Sound-absorbing materials often use the pore structure in the material. However, this pinhole structure usually leads to the transmission and propagation of sound waves. However, in order to prevent the sound from further transmitting from the material, it is necessary to reduce the cavity structure as much as possible and increase the density of the material.

Usually, the sound insulation performance of sound insulation materials is related to the density of materials. Buying high-density sound insulation materials can further improve the sound insulation performance of the room. However, the single-layer sound insulation material sometimes still has limitations. At this time, double-layer sound insulation treatment can be adopted, and additional damping materials can be added to the two-layer sound insulation material. However, it should be noted that the two layers of sound insulation materials should be avoided as much as possible to adopt the same thickness, so as to avoid repetition of coincidence frequency. If in the actual construction and decoration, the whole house should be soundproofed first, and then sound absorption and diffusion treatment should be carried out.

Post time: Apr-03-2023