This study investigates the aeroacoustics of a wing undergoing pitching motion in an anechoic wind tunnel at low Reynolds numbers. The study was made at wind speeds U ranges from 10 to 40 m/s, with the constant chord \(c=0.05\)  cm and a NACA 0012 wing at chord-length-based Reynolds number varying from \(3.2\times 10^4\) to \(1.3\times 10^5\) and pitching rate \(A=\dot{{\alpha _g}} c/2U\) ranges from 0.004 to 0.02, where \(\dot{{\alpha _g}}\) is the time variation rate of the geometric angle of attack. We synchronously measured the transient flow field and acoustic pressures using particle image velocimetry and wavelet-based beamforming methods to study the transient noise generation processes. The results reveal that tonal noise at different frequencies can be generated due to vortex shedding and surface pressure scattering at the trailing edge. The flow due to the leading edge separation can also interact with the boundary layer around the trailing edge, halting the tonal noise generation process. Broadband noise is generated on the trailing edge of the wing and wing tip, dominantly at high frequencies, and stopped when the \(\dot{{\alpha _g}}\) equals zero.