Some further investigations of the seat dip effect

The attenuation of low‐frequency sound, passing at near grazing incidence over audience seating, was investigated by examining spectra of the direct and early arriving sound. Detailed measurements in one hall and on scale model seats showed the frequency of the principal attenuation minimum to be related to the vertical angle of incidence as well as to the presence of additional early arriving sound energy. Octave band measurements in 11 halls demonstrated that the low‐frequency attenuation was strongly influenced by the geometry of the halls and in particular by the average ceiling height. Measurements of a string bass showed large level changes due to the seat dip attenuation, and this phenomena is concluded to play an important role in determining the perceived quality of a concert hall. These new results can be used to help design halls to minimize the negative effects of the seat dip attenuation.