Method and apparatus for controlling acoustic treatment of a sample including a liquid. A processing volume in which the sample is acoustically treated may be controlled, e.g., by positioning a suitable element so as to reduce and/or eliminate a headspace at a sample/gas interface. An interaction between the acoustic energy and the sample may be controlled, e.g., by using an energy director positioned at least partially in the sample that helps to reduce splashing or other sample ejection that would otherwise occur.