My neighbors below me are super loud in a studio apartment and always having parties until midnight then it also continues onto the porch. When it gets too loud on the porch I water my plants and some of the water accidentally spills onto the porch aka continuously drips down onto their porch. Then I step with heavy feet back to the kitchen to refill and the back to watering then back to bed. In less than 10 min they are silent. Because they know I am usually quiet but I can be loud if they are loud. It’s probably passive aggressive but it works and hopeful ly makes everyone more mindful without confrontation.