First, the value of sound pressure affect the distance to the equipment and the presence of reflecting surfaces. In addition, of great importance and location of the sound level meter, with which the measurements are made. For example, in the open space sound pressure level is reduced by about 6 dB for each doubling the distance from the source. The room is a similar reduction in sound pressure is already 3-4 dB. Permissible sound pressure levels for the different rooms are defined by sanitary norms.
In Technical Documentation noise characteristics of the equipment in accordance with standard cagi pneurop, should be presented in the form of sound pressure level in dB (A) measured at 1 m from the source (compressor). Speaking of compressors boge Kompressoren, note the following: among the smallest screw compressors, the sound pressure level at 1 m have compact compressors C – 59 dB (A) and cl – 59 dB (A), and the largest industrial compressors-S Series – 68-86 dB (A). Among the lowest rates of reciprocating compressors in series compressors srdl – 66 dB (A), and highest in compressors RH-85dB (A). As already mentioned, the power of sound decreases with distance from the noise source. This decrease can be calculated by a formula relating the power level and sound pressure level. For a given level of sound power (Lw), sound pressure level (Lp) at a distance r from the sound source is determined by the formula: Lp = Lw – lg r – 11 (dB). For example, if the power of the sound installation is 73 dB and is necessary to determine the sound pressure level at a distance of 10m, it will be: Lp = Lw – lg r – 11 = 73 – lg 10 – 11 = 61 dB.