The various methods of noise measurement. are available to determine the sound power. The calculation of the sound power may be performed by measuring the sound pressure in a soundproof room or in a free field or in an echo chamber. The environmental conditions must be considered in this case. A further possibility for determining the sound power is to measure the intensity of the noise in a measured area around the object. In doing so, environmental influences are eliminated to a certain extent. The calculation of the sound power is performed amongst other things in accordance with the DIN 45 635 Part 1 framework (Figure S 11) and DIN EN 23 741.
The sound power of a machine calculated under measurement conditions does not allow for a final statement to be made with regard to the noise emissions at the installation location. As a rough guide, it may be assumed that the hydraulics of a machine, considering all secondary measures will be at least 5 dB(A) higher in a free field than the pump in a soundproof room. The increase during installation will again be at least 5 dB(A).
This means that in order to keep within 85 dB(A), the pump must not exceed 75 dB(A) in a soundproof room.
Figure S 11: Measuring arrangements for sound in accordance with DIN 45 635, part 1