Sound / Energy
Our every day life is filled with undesirable sounds – noise. In order to damp it, several things have to be taken into consideration.
Energy and energy
We are dealing with two types of energy which have to be abosrbed in order to damp the noise around us to a minimum. The acoustic energy already in the air and the mechanical in the material, generating acoustic energy.
Sound in buildings and environments with a long resonance time (commonly known as echoing) is normally most disturbing. This might be the case in buildings with stone walls, ceilings or floors where the acoustic absorption of the sound energy is missing. When adding another source of sound to this, like a class of preschool children or some sort of noisy machines, the sound level will become too high and disturbing. By acoustic absorption of the sound energy, the resonance as well as the noise will be effectively damped. Typical absorbents are acoustic panels, thick draperies, thick carpets etc.
When a piece of material is exposed to mechanical energy by a blow or similar, sound is generated. In other words it ’sounds’ when the drumstick hits the cymbal. The kinetic energy of the drumstick is transmitted to the cymbal, creating resonance and generating sound. Now this was a desired sound but that is not always the case. Let us look at the car body: it is exposed to massive mechanical influences from the motor, the gear box, the bumpers etc. This is the undesirable sound. In other words we need something that can absorb the mechanical energy in the body sheet. Bitumen carpets glued to the metal of the car doors f. ex., are well known. The disadvantages with bitumen carpets are also well known, they are heavy and have a tendency to come off.