A 1:20 scale model has been constructed to investigate grazing attenuation by seats and audience at various angles of sound incidence, for both direct sound and early reflections. Transfer functions for a range of azimuth and elevation angles have been measured both for unupholstered seats and with modeled audience: these are referred to as the Audience Related Transfer Functions (ARTF). The measurements reveal not only the low frequency seat dip effect and its dependency on the incidence angle but also show a significant broadband attenuation. This broadband attenuation is strongly inversely dependent on the source elevation and can reach up to 16 dB between 400 Hz and 3 kHz. This has consequences equally for the direct sound and early reflections in auditoria. Subsequently scale model measurements using a finite size reflector to compensate for the mid frequency attenuation are discussed. A greater efficiency of audience coverage can be achieved with low-elevation early reflections (the so-called solid angle principle). Analyzing the measured ARTF, the reflection level also suffers from grazing attenuation inversely dependent on the elevation angle. Balancing the solid angle principle with the grazing attenuation, an optimized elevation for the reflection surface is proposed.

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