Audible noise has become a critical constraint in the construction of high-altitude ultra-high-voltage alternating current (UHV AC) projects. Currently, there is a lack of research on audible noise from UHV AC transmission conductors under extreme altitudes above 4000 m. This study, conducted at the Yangbajing High-Altitude Test Base in Tibet (4300m), employed a UHV corona cage and a BK sound measurement system to investigate the audible noise characteristics of three typical conductor configurations—8 × LGJ-1000, 10 × LGJ-630, and 12 × LGJ-500—under both dry and rain conditions. The audible noise levels under varying surface electric field strengths were systematically measured, and the coupling effects of rainfall and electric field intensity on noise generation at extreme altitudes were analyzed. Furthermore, using a typical 1000kV UHV AC single-circuit transmission tower configuration, a sound power calculation method was applied to evaluate the audible noise of transmission lines at 4300 m altitude. The findings provide essential references for the design and construction of UHV AC transmission lines in extremely high-altitude regions.