In multistory housing, sounds occasionally penetrate the walls and floors separating apartments. It may seem like this is a one-way flow of acoustic waves moving through built material from one inhabitant to another. In this article, I show that acoustic waves passing among apartments often move in more ways than just through built material. I propose a conceptualization of the auditory connection between neighbors as sonic relations that consist not only of concrete sounds but also of a range of abstract emotional layers, elements of personal histories, and interpersonal conflicts. Through an exploration of the accounts of two neighbors living in an early 20th-century building in Copenhagen, I show how the sonic relation between them can be understood as interfering in the domestic-personal spheres that shape both of them.