Impact of heat pump installation on the sound perceived by the owner
Noise emitted by heat pumps will not only affect neighbours but can also impact the owner, compromising living comfort. As outdoor units can be mounted in gardens, on façades, or on roofs, both airborne and structure-borne sounds generated by the heat pump can lead to noise inside the building. This paper discusses the relevance of both structure-borne and airborne sound transmission based on two distinct field measurements of heat pumps in operation. The first field measurement investigates interaction effects caused by two heat pumps located in the back garden of adjacent semi-detached houses by using a microphone arc measurements and psychoacoustic analysis. The second field measurement focuses on quantifying the structure-borne transmissions originating from a façade-mounted heat pump unit under various mounting scenarios. Microphone arc measurements showed that while fluctuation strength remained unaffected by combined operation, Roughness consistently peaked at a specific microphone position, possibly due to interaction. Tonal analysis also revealed a directional pattern: low-frequency fan tones were intrusive off-axis, whereas highfrequency tones were concentrated along the fan outlet axis, presenting a significant annoyance risk near building façades. Measurements on the façade-mounted heat pump show that structure-borne noise propagation is relevant to the level and tonality of indoor sound. It also shows that the mounting situation influences the transfer paths and the effectiveness of vibration isolators. In addition to the analysis presented in this paper, the data used in this study, along with supplementary analyses, will be available on the website of the IEA HPT Annex 63. This allows researchers and professionals to access the collected information and use it for further studies. Ultimately, this paper aims to raise awareness of the acoustic impacts of heat pumps on residents and highlights potential recommendations for future research.