A system for investigating physical properties of an object, the system comprising: an acoustic transducer apparatus arranged to apply to the object acoustic vibration localized in two or three dimensions in a region in the object; a transmitter arrangement arranged to illuminate the object with an illuminating electromagnetic wave having a frequency in a range extending down from 30THz simultaneously with the application of acoustic vibration, the vibration direction of the acoustic vibration having a component parallel to the propagation direction of the illuminating electromagnetic wave so that the vibration of the object caused by the acoustic vibration in the region generates a scattered electromagnetic wave including a set of Doppler components shifted from the frequency of the illuminating electromagnetic wave by frequencies of the vibration of the object caused by the acoustic vibration and multiples thereof; a receiver arrangement arranged to receive the scattered electromagnetic wave generated in the region; and a signal processing apparatus arranged to derive, from the received scattered electromagnetic wave generated in the region, data representing at least one characteristic of the Doppler components, characterized in that: the transmitter arrangement comprises an antenna coil surrounding, through at least 180 degrees, an axis along which at least a portion of the acoustic vibration from the acoustic transducer apparatus is output, and the coil is fixedly connected to the acoustic transducer apparatus and configured to illuminate the object with the coil and the acoustic transducer apparatus located on a same side of the object. an acoustic transducer apparatus arranged to apply to the object acoustic vibration localized in two or three dimensions in a region in the object; a transmitter arrangement arranged to illuminate the object with an illuminating electromagnetic wave having a frequency in a range extending down from 30THz simultaneously with the application of acoustic vibration, the vibration direction of the acoustic vibration having a component parallel to the propagation direction of the illuminating electromagnetic wave so that the vibration of the object caused by the acoustic vibration in the region generates a scattered electromagnetic wave including a set of Doppler components shifted from the frequency of the illuminating electromagnetic wave by frequencies of the vibration of the object caused by the acoustic vibration and multiples thereof; a receiver arrangement arranged to receive the scattered electromagnetic wave generated in the region; and a signal processing apparatus arranged to derive, from the received scattered electromagnetic wave generated in the region, data representing at least one characteristic of the Doppler components, characterized in that: the transmitter arrangement comprises an antenna coil surrounding, through at least 180 degrees, an axis along which at least a portion of the acoustic vibration from the acoustic transducer apparatus is output, and the coil is fixedly connected to the acoustic transducer apparatus and configured to illuminate the object with the coil and the acoustic transducer apparatus located on a same side of the object. the transmitter arrangement comprises an antenna coil surrounding, through at least 180 degrees, an axis along which at least a portion of the acoustic vibration from the acoustic transducer apparatus is output, and the coil is fixedly connected to the acoustic transducer apparatus and configured to illuminate the object with the coil and the acoustic transducer apparatus located on a same side of the object.