A focusing arrangement (100) for focusing particles or cells in a flow. The arrangement comprising at least one channel (110) for guiding the flow, the channel comprising at least one particle confinement structure comprising particle flow boundaries (112) and at least one acoustic confinement structure (120) comprising acoustic field boundaries (122) adapted for confining acoustic fields, wherein the acoustic field boundaries (122) are different from the particle flow boundaries (112) and wherein the at least one acoustic confinement structure (120) is arranged with regard to the channel (110) to confine acoustic fields at least partially, in the channel (110).
