Aircraft surfaces often feature various geometric discontinuities, such as small cavities, slot cavities, and protrusion envelopes. The airflow interacting with these structures can generate aerodynamic noise through coupled flow-structure interactions, adversely affecting cabin acoustics and community environments. This study investigates the noise characteristics and noise-reduction strategies for these typical configurations. Findings reveal that the dominant noise source for “closed-type” shallow circular cavities originates from flow separation at the lip region and the cavity rear; for “open-type” circular cavities, self-sustained oscillation modes at the lip are predominant, with cavity internal acoustic modes playing a secondary role. In deep circular cavities, the noise-generation mechanism gradually evolves toward internal cavity modes. To mitigate the prominent tonal peaks of circular cavities, reducing energy injection or alleviating post-wall flow impingement can suppress peak noise levels by over 10 dB. Noise from protrusion envelopes is primarily caused by flow separation, exhibiting broadband characteristics. For square and rectangular protrusion envelopes, shape optimization reduces drag by more than 80% and noise by over 5 dB. Slot cavities generate noise predominantly at their openings and due to periodic separation loads induced by stepwise flow splitting, with spectra characterized by mid-to-high-frequency humps. Flattening the stepwise height difference or embedding damping strips inside the cavity effectively reduces such hump noise by over 7 dB. This research provides insights into the noise mechanisms of geometric discontinuities on aircraft surfaces and demonstrates viable mitigation approaches through structural and acoustic optimization.