In this study, the influence of different design parameters, such as core density, core material, and cell size on the wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material configurations. The shear modulus of the core showed maximum influence on the wave speeds of the samples, while cell size did not have a significant influence on the wave speeds or on the transmission loss. Skin material affected wave speeds only in the pure bending regime. Honeycomb sandwich structures with a subsonic core and reduced wave speed showed increased transmission loss compared to samples without a subsonic core.