| 主权项 |
1. A loudspeaker adapted to convert an input electrical signal representing sound information into acoustic signals comprising:
a signal processor adapted to generate, at an output, from the input electrical signal, an electrical signal modulated by means of a carrier having a frequency substantially higher than 20 kHz; and a source capable of producing ultrasonic signals from the modulated electrical signal and diffusing said ultrasonic signals through a medium, wherein the carrier is chosen so that the acoustic signals are at least partially produced during crossing of the medium by the ultrasonic signals, and wherein the source comprises groups of at least two piezoelectric transducers, each group comprising a buffer device coupled between said at least two piezoelectric transducers of the group and the signal processor, the buffer device of each group being adapted to enable transmission of the modulated electrical signal to said at least two piezoelectric transducers of the group and to maintain the voltage observed at the terminals of said at least two piezoelectric transducers of the group substantially equal to the voltage observed at the output of the signal processor. |
