The emergence of the area of nanophononics requires the development of terahertz (THz) acoustic devices with tailored properties. We describe nonperiodic planar nanostructures with specific THz phononic response and superior performance. We show that improved devices based on GaAs and AlAs layers can be designed using an optimization Nelder-Mead simplex method, and grown with state-of-the-art molecular beam epitaxy. We also demonstrate that high-resolution Raman scattering provides a powerful tool to characterize these devices. We illustrate the concept with results on acoustic THz edge and color filters. (c) 2006 American Institute of Physics.