Open database with frequency- and directivity-resolved acoustic source data to improve heat pump placement
Heat pumps are gaining popularity due to their high efficiency and carbon-neutral operation, if using renewable energy sources. Among them, air source HPs are particularly favored for their affordability and straightforward installation. However, ensuring optimal placement of outdoor units to minimize receiver noise levels is crucial for the acceptance of HPs. Currently, predicting noise propagation for HPs is challenging due to the lack of frequency- and directivity-resolved acoustic source data. Standardized acoustic test procedures based on the sound intensity measurement technique (ISO 9614) are employed to obtain frequency-resolved partial sound power levels for the five faces enveloping the HPs. Measurement data gained according to ISO 3744 with a cubic enveloping surface, can be converted to the same format for comparability. These data provide the directivity information needed to improve placement. In the framework of IEA HPT Annex 63, we extend an open, anonymized database that links directivity- and frequency-resolved sound power data of outdoor units of air source HPs with related data on geometry, operating conditions and measurement methodology. Compared with earlier Annex 63 publications based on 27 units measured at CETIAT and AIT, this paper adds measurements from Fraunhofer IBP and Empa and presents a first cross-laboratory statistical analysis of five comparable units that quantifies how the orientation of fan, heat-exchanger and blind faces affects directional sound radiation. The analysis reveals patterns, such as approximately 10 dB higher radiation at the heat-exchanger face above 2 kHz and about 5 dB shielding by blind faces below 2 kHz, which can be directly translated into placement recommendations. The database is open for additional contributions and can include data of sound intensity measurements, measurements according to ISO 3744 using a cubic enveloping surface and other measurements performed in free field over a reflecting plane with arbitrary microphone positions.