Recording Shielding System Based on Ultrasonic Waves

This system uses the STM32H750 microcontroller as its core to implement an ultrasonic-based blocking recording shielding system through a recording shielding signal generator and an audio signal monitoring and recognition module. It includes recording shielding and audio monitoring and recognition functions. The shielding range can be adjusted by modulating the output power. The microcontroller controls the amplitude and frequency of the output shielding signal by controlling the direct digital frequency synthesizer (DDS) module, which in turn adjusts the intensity of the emitted ultrasonic waves. After passing through a Class D amplifier, the shielding signal can drive the ultrasonic transducer to emit ultrasonic waves, thereby blocking audio signals to achieve the recording shielding effect. The system also converts audio signals into electrical signals that can be captured by the microcontroller's on-chip analog-to-digital converter (ADC) through a microphone module, low-pass filter, and DC bias circuit. It calculates the zero-crossing rate(ZCR) and spectral centroid(SC) of the acquired voltage array to determine whether there is an audio signal in the environment and to recognize the types of audio signals.The system also utilizes wavelet analysis and neural networks to improve the accuracy of monitoring and recognition.