Optimization of vibrating panel loudspeakers

Abstract

The sound radiation from vibrating panel loudspeakers at sub-critical frequencies originates from discontinuities such as boundaries, abrupt changes in material or shifts in the force field. In the scope of this thesis work, the effect of introducing additional passive discontinuities to vibrating panel loudspeakers are investigated in view towards an increase in radiated power. Two groups of structures are treated, i.e. finite and infinite structures. The first group in reality represents distributed mode loudspeakers, due to the modal vibration which is associated with finite structures, while infinite structures stand for bending wave loudspeakers. The radiated power is obtained by integrating over the FOURIER transform of the spatial velocity distribution. For further analysis, the sound intensity directly on the structure is calculated. The proper placement of discontinuities of point-mass type on infinite structures is shown to lead to an increase in radiated power as the available vibrational energy on the structure is more efficiently utilized for the generation of sound waves. For the case of finite structures which are already optimized for sound radiation, it is found that the introduction of additional discontinuities does not result in a gain in radiated power.