Interesting facts about sound

The standard sound level difference is a measure in decibels [dB] for the attenuation of a building component from external noise. It describes how much noise can penetrate from the outside to the inside through the component. Higher values are advantageous, as the attenuation of the noise is then greater. The higher the standard sound level difference, the more noise is absorbed by the component. 3 dB more corresponds to a halving of the volume, as the standard sound level difference  is not specified linearly but logarithmically.

It is also important to differentiate between the sound from outside and from the ventilation unit itself. Without comparative measurements, it is practically impossible to distinguish between the two. The filtering of ambient noise is also problematic. For example, there are often sound components that cannot be perceived, but which the measuring device reproduces as an average value.

The positioning of the ventilation units is also crucial. Depending on the installation location and the associated possible sound reflections, the volume of a fan can vary greatly. Fans in the corner of a room can be up to 9 dB louder than when positioned directly on a free wall. The size and nature or furnishings of a room also play a role in the development and perception of sound. For example, a sound source in a small, reverberant room, such as a tiled bathroom, can have a significantly louder effect than in a large living room, which has various sound-absorbing surfaces thanks to carpets, curtains and upholstered furniture.