The noise spectral characteristics and noise reduction schemes of screw air-source heat pump: A case study

The screw air-source heat pump can cause incessant high noise levels during operation, which might hinder adoption of this energy-efficient heat pump. First, acoustic measurements and comparison testing were performed in this research. The measurements revealed that the compressor is the main noise source of the heat pump, and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions, with multiple peaks at 63, 250, and 1000 Hz. Then, a compressor sound insulation cover with broadband absorption was proposed, and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA. Third, we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation. The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump. The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ΔLd exhibit a U-shaped relation. For buildings of different heights, the optimal heights of noise barrier are proposed. The 5.5-meter is the optimal height of the sound barrier for single-story buildings. The conclusions can be applied to other building projects for heat pump noise reduction.