Soundproofing - Insulation

Airborne sound insulation (also known as sound isolation) refers to the reduction of sound transmission through a separating surface (sheet metal). With a hard surface, sound waves are primarily reflected, causing the sound level in the passenger compartment or in the door to increase. To counteract this effect, composite materials combining sound insulation and sound absorption are often used. Sound insulation is achieved by increasing the weight per unit area of, for example, sheet metal using flexible insulation mats. Airborne sound insulation is frequency-dependent; the lower the frequency, the higher the weight per unit area must be.