The objective of present work is to improve the transmission loss of a barrier separating two acoustic spaces and subjected to low frequency harmonic excitation. A novel concept of achieving this is proposed through addition of point mass at the optimal location over the barrier surface. This allows for a local control of the radiated noise at the target location through the directivity pattern. Analytical expressions to find the structural response to the normally incident acoustic excitation on the planar barrier is derived and validated by a finite element simulation. Rayleigh integral is then used to calculate the sound pressure. The complete procedure is non-dimensionalized for generalization. The optimal location of mass to minimize sound radiation at a receiver location is obtained using numerical optimization. Point mass attachment at the optimal location results in major sound pressure reduction at the target location which is much more than those obtained by uniform distribution of mass over the plate. The total energy radiated over the entire transmission region is also reduced. However, the reduction in total transmitted energy is smaller than the reduction achieved at the specific target location. Passive techniques to improve the transmission loss of a barrier in global sense works well for high frequency whereas, active techniques spans the low frequency range. But active control methods are costly and difficult to implement and hence local control in the transmitted sound using passive techniques could be an alternative. Copyright© (2013) by Austrian Noise Abatement Association (OAL).