The Scaled Boundary Finite Element Method (SBFEM), is a semi analytical method, incorporating the best features of both the finite element method and the boundary element method (BEM). It is proposed to study 2D acoustic problems in the mid-frequency range using this technique. Since only the boundary needs to be discretized, the proposed framework reduces the computational burden. A systematic numerical study shows that the SBFEM outperforms FEM, especially when the domain geometry is complex. For a typical 2D car cavity, accurate results with 42% reduction in degrees of freedom is demonstrated. Guidelines for effective mid-frequency analysis of acoustic cavities by SBFEM, have been formulated based on the results obtained.