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S. Hinterseer, T. Bednar:
"Noise Emissions of Air Source Heat Pumps - Defrosting Cycle";
Talk: Jahrestagung der Österreichischen Physikalischen Gesellschaft, Graz; 2018-09-11.

The role of heat pumps for space heating is becoming more and more significant in Austria and Europe. Especially in single-family detached homes, the air source heat pump is becoming a standard heating system. Since the heat source is outside air, it is typical for such a device to make use of an outside heat exchanger unit. This will cause noise emissions, which have to be accounted for in acoustic planning, e.g., calculating the required minimum distance of the outside unit to sensitive areas like bedroom windows. The noise emission specifications on these devices represent a state of standard operation. Other operating points, most notably the defrosting of the heat exchanger, can be significantly louder. The main goal is to examine the noise emissions of an air source heat pump at different points of operation. This is done inside a conventional acoustics test facility. Since such a facility does not offer the simulation of outside air, fan heaters and ultrasonic humidifiers are used to ensure constant temperature and humidity levels.
The paper presents spectra and sound power levels at standard operation points which are currently used for the declared sound power level. Additionally the sound power levels and spectra over time during typical operation phases are presented and discussed.