HVAC appliances cause sound in buildings. These devices consist of elevators, sewers and water pipes, compressors, ventilation units, cooling and air conditioning units and heating units. In residential buildings the sound pressure level produced by HVAC appliances has to be low enough not to disturb sleeping or other activities, and it shouldn?t be too high outside the building, either.

The noise of different devices is often time-dependent.This is why the highest allowed sound pressure level in the National Building Code of Finland has been announced as two different values. The maximum A-weighted maximum value, LA,max, allowed in residential rooms is 33 dB. To receive a proper result from measuring the HVAC appliances, the time phase has to be long enough. For example, sewer noise measurement lasts from flushing the toilet to the point when the waiste has gone through the sewer pipe. During this period also the A-weighted equivalent sound pressure level, LA,eq,T, is measured. Highest allowed value for LA,eq,T is 28 dB.