Redistribution of the low frequency acoustic modes of a room: a finite element-based optimisation method

This paper presents a method to redistribute the acoustic modes of a room in the low frequency range. The relationship between the acoustic modes and the room geometry is studied. The fundamental problem of normalizing the acoustic modes of a simple, orthogonal room is examined in depth. Several variable local geometric modifications of the room walls are introduced and an optimisation procedure is developed, based on finite element analysis. This procedure is used for the calculation of the exact magnitude of the geometric modifications that will lead to smoother mode and consequently, smoother sound energy distribution in the frequency range of interest. The sound quality improvement of the modified room in the low frequency range with respect to ISO recommendations is verified. This work opens up the possibility of constructing acoustic laboratories with extended suitability to perform acoustic measurements in the low frequency range.