Air conditioner installation can be moderately to significantly noisy, particularly during the drilling phase, which involves using a rotary hammer or core drill to bore through concrete or hollow block walls. This part of the process typically lasts only a few minutes but produces considerable noise and vibration. Mounting the bracket, securing the outdoor unit, and testing the system are comparatively quieter tasks. If you live in a condominium or apartment building, it is courteous to inform your neighbors in advance about the scheduled installation, as the drilling noise may be audible in adjacent units, and some buildings restrict noisy work to specific hours during the day.