Propagation and interference of thermal waves in turbulent thermal convection

We report investigation of thermal waves in harmonically modulated turbulent ther-mal convection in a Rayleigh-Benard cell. We probe the thermal waves in the working fluid-cryogenic helium gas-by temperature sensors placed in the cell and embedded in the plates. We observe propagation and interference of two coherent thermal waves and describe their behavior in terms of models that explain the weak attenuation and apparent superposition of thermal waves in the bulk, accounting for the temperature profile of convective turbulent flow via a spatially dependent effective thermal diffusivity.