From the research Heat
From the research Heat pumps Fig. 4: The artificial heads are placed at a distance of one metre from the heat pump. Sound engineer Benjamin Müller and psychologist Lisa-Marie Wadle measuring the distance. of the sound recordings. The distance between the artificial head and the heat pump was one metre. This way, the team was able to record many different sounds. The test persons then assessed the recorded sounds in the High-Performance Indoor Environment Lab (HiPIE Lab) of the Fraunhofer IBP. Exactly the same conditions in terms of acoustics, lighting, indoor climate and air quality prevail there at all times. The test persons listened to 44 sounds one after the other and classified them in a first step on a scale of one to ten by answering the questions “How annoying is the sound?”, “How loud is the sound?” and “How well can the sound be ignored?” In a second step, the test persons heard two different sounds and put them in relation to each other. Sound A>B (A is more annoying than B), A=B or A
From the research Heat pumps Fig. 6: The results of the auditory experiments help develop low noise heat pumps such as the Logatherm WLW196i with SILENT Plus technology. of the heat pump also influences the perceived loudness. For example, people assess the sound of a heat pump as louder when they see the fan and quieter when the fan is concealed behind a cover. Buderus has therefore revised the outdoor unit of the WLW196i..AR S+ and fitted it with a diffuser. The new geometry of the fan moreover contributes to the fact that the sound does not propagate directly forwards, but along the diffuser outlet, which attenuates it. Conclusion In addition to optimising the technical parameters to increase the efficiency of heat pumps as an environmentally friendly alternative to conventional methods of heat generation, their noise emissions are a key issue. In view of the increasing use of heat pumps, especially in confined spaces, and the growing sound and noise pollution caused by multiple noise sources, psychoacoustic studies are becoming more and more relevant. Otherwise, there is a risk of paying for positive environmental effects such as energy savings with noise pollution. Buderus is not only continuously further developing its products in terms of actual sound level, but also takes the results of psychoacoustic studies into account. In cooperation with the Fraunhofer IBP, Buderus therefore conducted auditory experiments to develop a forecast formula for the perceived annoyance of heat pump sounds. Buderus thus reduces the expected annoyance so as to further increase the acceptance and use of heat pumps as a sustainable form of heat generation. The Author: Hans-Jörg Risse, Product Manager Sales Technical Support Heat and Cold Generators Buderus Germany GREEN EFFICIENT TECHNOLOGIES 2023 27
