Compressor Noise: The core noise source, accounting for 60%~70% of the total unit noise. Reciprocating compressors produce mechanical impact noise (65~85dB) due to the reciprocating motion of pistons, which becomes more noticeable especially when the load fluctuates. Although screw compressors operate more stably (60~75dB), high-frequency noise is still generated during rotor meshing and oil-gas separation. If the bearings are worn or the gaps are abnormal, sharp abnormal noises will also occur.

Fan Noise: Including noise from condensation fans and cold fans. Condensation fans (outdoor units) generate airflow noise (55~70dB) as fan blades rotate and cut through air. If the blades accumulate dust, become deformed, or the motor bearings age, vibration noise will accompany it. Cold fans (indoor) are prone to low-frequency humming (50~65dB) due to unbalanced fan rotation in low-temperature environments or the operation of defrosting mechanisms. Slight airflow noise is also produced when airflow passes through the evaporator fins.

Pipeline and Component Noise: When refrigerant flows at high speed in pipelines, if there are sudden changes in pipe diameter, excessive bends, or impurities, "hissing" airflow impact noise (45~60dB) will occur. If the unit base has poor shock absorption, vibrations from the compressor and fan will be transmitted to the ground or walls, causing structural resonance noise. When solenoid valves and expansion valves start or stop, the movement of valve cores also produces short-term impact noise (40~55dB).

Other Auxiliary Noises: Such as slight vibration noise from components like liquid receivers and oil separators due to pressure fluctuations, or "click" sounds when electrical components (contactors, relays) engage. These noises are usually low (35~50dB) but will affect the overall acoustic environment when superimposed with other noises.