SOUND REPRODUCTION DEVICE

摘要

A sound reproduction device includes a modulator having an output terminal for outputting a modulated carrier wave signal obtained by modulating a carrier wave signal in a ultrasonic band with an audible sound signal, a super-directivity loudspeaker connected to the output terminal, a capacitor connected between a ultrasonic wave source and a ground, first and second current detectors for detecting currents flowing through the super-directivity loudspeaker and the capacitor, a high-pass filter for outputting a filtered signal obtained by eliminating a low-frequency band component of the current detected by the first current detector, and a differential amplifier unit for outputting a signal corresponding to a difference between the filtered signal and the current detected by the second current detector. The ultrasonic wave source is configured to output the carrier wave signal such that the signal output from the differential amplifier unit is constant.

主权项

1. A sound reproduction device comprising:
an ultrasonic wave source for outputting a carrier wave signal in an ultrasonic band; a modulator having an output terminal for outputting a modulated carrier wave signal obtained by modulating the carrier wave signal with an audible sound signal; a super-directivity loudspeaker including a piezoelectric element and a diaphragm driven by the piezoelectric element, the piezoelectric element being connected electrically between the output terminal of the modulator and a ground; a first current detector for detecting a current flowing through the piezoelectric element; a capacitor connected electrically between the ultrasonic wave source and the ground; a second current detector for detecting a current flowing through the capacitor; a high-pass filter for outputting a filtered signal obtained by eliminating a low-frequency band component of the current detected by the first current detector; and a differential amplifier unit including a differential amplifier for outputting a difference between the filtered signal and the current detected by the second current detector, the differential amplifier unit being configured to output a signal corresponding to the output difference, wherein the ultrasonic wave source is configured to output the carrier wave signal such that the signal output from the differential amplifier unit is constant.