The present paper is a review of the author’s work on sound reflections covering a span of years starting from 1982. After a study of the reflection properties of curved surfaces, the diffraction effects related to single reflectors was studied, both theoretically and experimentally. The main result was a characteristic frequency above which the sound reflection is fully efficient as long as the reflection point is within the reflecting surface. Next, the array of reflectors was studied, and again the characteristic frequency was found useful as a design parameter, but here as an upper frequency limit for reliable reflections. The design principle was successfully applied in a concert hall in Copenhagen. Recently, the reflection of a spherical sound wave emitted from a point source has been studied and a theoretical model has been developed. An application of this model is for the sound propagation over an area with sound absorbing properties like those of a seated audience in a large auditorium.