The invention relates to a process and apparatus for ultrasonic assisted drying of materials, in particular, but not exclusively, for the low temperature drying of materials that are heat sensitive. In particular, there is provided an apparatus for dehydration of water containing material comprising: an ultrasound emitter; an ultrasound transmission platform that directly or indirectly supports said material; a fluid retained between said emitter and said platform, through which ultrasound energy is transferred; and a gas stream device that directs drying gas to said material. There is also provided a method of dehydration of water containing material comprising locating the material either directly or indirectly on an ultrasound transmission platform of a dehydration apparatus that comprises: an ultrasound emitter; a fluid retained between said emitter and said platform, through which ultrasound energy is transferred; and a gas stream device that directs drying gas to said material; and exposing said material to ultrasound energy and drying gas flow for a time and under conditions suitable to achieve desired extent of dehydration of said material. In another aspect there is provided a material that has been dehydrated using the method or apparatus described above.