Analysis of the seat-dip effect in an opera house

This paper focuses on the analysis of measurements in a Finnish opera house with respect to the seat-dip effect. The effect features an attenuation of low frequencies due to sound waves arriving at small incidence angles to the tops of the seat backrests and bending between seats before interfering destructively with the direct sound at the listener's ears. In opera houses with most source positions in the pit, the direct sound first diffracts from the pit rail or edge before propagating to the audience across the seats, while in concert halls the direct sound path is unobstructed. This paper shows that the seat-dip effect in opera houses and in concert halls behaves similarly. However, in the opera house especially in the front part of the parterre, the angle of incidence differs significantly between stage and pit sources, thus yielding a difference in their seat-dip attenuation. This may have some implications for the balance between the orchestra and the singers. The results further show that the depth of the orchestra pit has no influence the seat-dip attenuation, whereas the height of a solid pit rail affects mostly the magnitude of the attenuation.