Sound insulation

 

In order to reduce noise, it is important to distinguish between air sound and contact sound. Air sound is created because a sound source directly vibrates the air (music). Contact sound is created by vibrating a construction and thereby creating sound (compressor, sound of walking on floor). Air sound vibrates constructions which pass on the sound. Sound vibrations can be carried much further in a construction than they can via the air.

The sound in the space where the sound source is located therefore has to be reduced in order to prevent hearing damage and to prevent the sound transferring to other spaces. This can be achieved by absorbing the sound. This technique is also used to reduce the reverberation time and to improve the acoustics of an auditorium for instance. Sound absorption transfers the sound energy into heat through friction.

We call the prevention of sound being transferred to other spaces insulation. Firstly, we have to see whether the sound cannot just transfer through the air. Possible sound leaks have to be closed first. In order to keep airflow going, special constructions are applied (e.g. acoustic louvers) which do let air through, but shut out as much sound as possible.

Then, constructions have to be prevented from vibrating. In first instance this might be achieved by detaching the source of the contact sound from the construction which passes the vibrations on. The more mass a construction has, the more energy is needed to vibrate it. So by increasing the mass, the sound is insulated.

In addition to the absorption and insulation factor, mechanical, temperature and flammability characteristics also apply when choosing a material in a certain application.