An ultrasound system (1) is disclosed that comprises a probe (10) including an array (110) of CMUT (capacitive micromachined ultrasound transducer) cells (100), each cell comprising a substrate (112) carrying a first electrode (122) of an electrode arrangement, the substrate being spatially separated from a flexible membrane (114) including a second electrode (120) of said electrode arrangement by a gap (118)； a voltage supply (45) coupled to said probe and adapted to provide a first set of said CMUT cells with a sequence of drive voltages each including a bias voltage component and a stimulus component of different frequency for generating a series of temporally distinct pulses each having a different frequency, wherein each pulse is generated in a separate transmit mode and provide a second set of said CMUT cells with a sequence of temporally distinct bias voltages, wherein each temporally distinct bias voltage is provided in a receive mode following one of said transmit modes and is for setting the second set of CMUT cells to a resonance frequency corresponding to the pulse frequency of said transmit mode； and a signal processing unit (22) communicatively coupled to said array and adapted to superimpose the echo signals received by the second set of CMUT cells during the respective receive modes. An ultrasonic imaging method using such a system is also disclosed.
