Abstract: The invention relates to a method for masking noise as well as a control device and a masking system for carrying out said method. According to the invention, several zones in a room are independently exposed to soft sonic radiation in a basic state for masking purposes. The masking system thus comprises means for independently exposing zones in a room to sonic radiation. The masking system further comprises means which allows noise generated in a zone to be registered and preferably also be analyzed. The masking exposure to sonic radiation is reduced in the zone in which the external noise was generated and/or the masking exposure to sonic radiation is increased in the other zones in accordance with the measured or registered noise and, if applicable, the result of the analysis of the measured external noise. All in all, this allows the level of masking noise to be kept low compared with the prior art while very reliably achieving the desired masking effect.

Abstract: To provide an inexpensive, slender sound absorber, it has a plurality of porous layers or regions of different densities and different flow resistances respectively. Of significance are the boundary surfaces between the different, porous layers which are accompanied by changes in impedance. Homogenized and adapted flow resistance conditions should be avoided. Although the thermal frictional effect in the porous material is desired, in particular to absorb higher frequencies, according to the present invention it only forms one element of the absorptive working mechanism. In addition, the effect known in physics as refraction is used. At the boundary layer between two materials of different density and different flow resistance respectively there is an abrupt change in impedance. This leads to a phase shift of the sound wave, and so a sound absorbing effect is made possible.

Abstract: To provide an inexpensive, slender sound absorber, it has a plurality of porous layers or regions of different densities and different flow resistances respectively. Of significance are the boundary surfaces between the different, porous layers which are accompanied by changes in impedance. Homogenized and adapted flow resistance conditions should be avoided. Although the thermal frictional effect in the porous material is desired, in particular to absorb higher frequencies, according to the present invention it only forms one element of the absorptive working mechanism. In addition, the effect known in physics as refraction is used. At the boundary layer between two materials of different density and different flow resistance respectively there is an abrupt change in impedance. This leads to a phase shift of the sound wave, and so a sound absorbing effect is made possible.