Soundproofing, also known as sound blocking, refers to insulated materials that prevent the passage of sound. Soundproofing materials tend to be heavy, solid, dense and thick and it is a very useful solution when dealing with unwanted noise. Cinemas, TV and radio stations, as well theatres frequently have sound blocking systems within their facilities.
Soundproofing is not always a perfect system regarding acoustics because the main goals are to improve the reverberation within a room and to reduce sound leakage to and from adjacent rooms or outdoors. Producers often use acoustic quieting and noise control to limit unwanted noise. In these scenarios, soundproofing can suppress unwanted indirect sound waves that cause echoes, and resonances that cause reverberation. Soundproofing can reduce the transmission of unwanted direct sound waves from the source to an involuntary listener through the use of distance and intervening objects in the sound path.
When dealing with sound blocking, it’s essential to consider the following: distance, damping, and absorption. Regarding distance, the energetic density of sound waves lessens as they spread out so that increasing the distance between the receiver and source results in a progressively lesser intensity of sound at the receiver.
Damping refers to the resonance reduction process within a specific space. This resonance reduction is achieved either by absorption of by redirection. Absorption is meant to reduce the overall sound level, whereas redirection transforms unwanted noises into harmless or even pleasurable sounds by reducing coherence. Damping can either reduce the acoustic resonance in the air or the mechanical resonance in the structure of the room.
Absorption can spontaneously transform part of the sound energy into a very small amount of heat in the intervening object. There are many materials that can absorb sounds in several ways, so the choice should be based on the frequency distribution of the noise to be absorbed, as well as on the required acoustic absorption profile.