Methods of Device Noise Control

Technological development has a high impact on the everyday life of humans and their working conditions. Noise generated by devices is an important problem in numerous environments. Such a problem is explored in this chapter. A classical protection solution is to apply passive sound insulating materials. However, passive barriers are often ineffective, especially at low frequencies. They may also be inapplicable due to technical reasons. An alternative way is to use active control methods. If a device generating noise is surrounded by a thin-walled casing, or if it can be enclosed in an additional casing, control inputs can be applied directly to the structure, and as a whole the casing can be used as an active barrier enhancing acoustic isolation of the device. If appropriately implemented, it results in a global noise reduction instead of local zones of quiet. The aim of the authors is to present the theoretical basis for developing active device casings. The chapter presents exemplary plants, discusses the principles of building a mathematical model and using it to build optimal noise reduction systems, passive, semi-active and active. Examples of results confirming the development of a new concept of global noise reduction for machines and devices are given.