Abstract: The mechanism of refrigerant flow sound in commercial air conditioning was studied through a combination of experiments and simulations. It is found that there is a cavity resonance phenomenon between the electronic expansion valve B tube and the reducing joint in the cavity area. Based on the distribution characteristics of acoustic cavity modes, an improvement measure for the integration of reducing joints was proposed, which improved the key frequency band of refrigerant flow sound by more than 3 dB (A) and significantly improved the listening experience.

Key words: Refrigerant flow sound, Vocal modality, Reducing joint