Extra or ultra-high voltage transmission lines can exhibit strong corona discharge and generate severe audible noise (AN) at high altitudes

which has become a critical limiting factor for power lines construction. However

the AN data of bundle conductors at high altitudes are very rare

which cannot adequately support the power utilities to make reasonable conductor selections. In this paper

a sound pressure level (SPL) of 14 types of bundle conductors is investigated by using an ultra-high-voltage (UHV) corona cage (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8\ \mathrm{m}\times 8\ \mathrm{m}\times 35\ \mathrm{m}$) at an altitude of 2216 m

where the bundle numbers between 4 and 12 and the conductor types are used in 500 kV

750 kV or 1000 kV power transmission projects. Then a large number of valuable AN data are obtained; the influences of bundle numbers and sub-conductor diameters on an acoustic power density level (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{\text{PWL}}$) are analyzed; and an A-weighted <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{\text{PWL}}$ calculation method is proposed. In addition

by comparing the AN data obtained from the low-altitude area (altitude: 23 m)

the AN altitude correction factor is concluded

and the influences of conductor parameters and the surface electric field strength on correction factors are discussed. The results obtained in this paper can provide important data for the construction of high-altitude AC power lines.