Abstract: The present invention relates to ultrasonic resonators comprising a resonator chamber body (11) and one or more electroacoustic transducers (13, 14). The resonator body consists of a non-piezoelectric material; it forming a resonant cavity for accommodating a specimen. This resonant cavity is configured so that between the acoustically excitated internal walls a resonant wave field of standing linear acoustic waves is formed. The electroacoustic transducer(s) is(are) acoustically coupled externally to said resonator chamber body (FIG. 2) fixedly or removably or movably.

Abstract: A direct digital synthesizer (DDS) (1) or digitally operating function generator has one or more channels (A, B, . . . ) each with a phase increment register and is controlled by means of a computer system (2) (e.g. a PC) by the computer system (2) sending bits of information to the DDS.(1). Each of the phase increment registers has a given bit width and in operation at every point in time a stored phase value P. The addition of a phase increment Q of a certain bit length is achieved by specific steps in the method by means of which an overflow is avoided. In control a hardware protocol (4) with a multiplexer ensures that the bits of information sent by the computer system (2) are effective in the DDS (1) either as address bits or as data bits.