'Humming' or 'Hissing'? - Psychoacoustical investigation of sounds from heat pumps

摘要

Heat pumps, which become increasingly popular as heating systems for houses, with the build-in fan as main acoustic source could be annoying for the neighborhood. Previous jury tests with a semantic differential reveal that besides the psychoacoustic loudness and sharpness, temporal structures in a sound signal have a significant impact on the quality evaluation of fan noise. In this context, the blade passing frequency (BPF) and its harmonics play an important role. It emerges, that distinctive sound patterns rated "helicopter-like" by acoustic experts especially when tonal signatures in the signal are amplitude modulated with BPF. From a further jury test based on synthetic generated sounds, which were derived from measured fan sounds in heat pump applications, two different evaluation clusters with opposing assessments were determined: one major group, which prefers the "hissing of the fan" and a smaller group, which favors the "humming of the electric motor". In an attached interview some participants of the test describe a "harmonic balance" of the two mentioned sensations as ideal. By changing the blade shape of an axial fan, design optimizations should be investigated psychoacoustically. Therefore the annoyance will be predicted based on the previous results and directly measured in a jury test.