Measurements of sound absorption coefficients of raked audience seating in a rectangular scale model room

Despite its significance, the sound absorption property of seating has not been fully understood compared to the other surfaces in an auditorium. In particular, the lack of information for sound absorption by seating with changes in section may lead to a failure in accurate prediction of room acoustics. This research investigates the effect of floor rake angle change on the sound absorption property of seating through a series of measurements performed in a rectangular scale model room. Both the sound absorption coefficients (alpha A) of unoccupied and occupied seating are measured using combinations of three different types of scale model chairs and two different types of scale model auditors while the floor rake angle is systematically varied. The results suggest that the alpha A's for both unoccupied and occupied seating significantly increase as the floor rake angle becomes larger. However, the relationship between the floor rake angles and the corresponding alpha A's is not monotonous. The effect of changing floor rake is highly associated with the upholstering of chairs for unoccupied seating, whereas it critically depends on the sound absorption property of auditors rather than the upholstering for occupied seating.