基于声学参量阵理论的超声波防录音屏蔽研究与实现

随着智能设备的快速发展，利用一些录音设备诸如智能手机、录音笔等窃取信息的手段显得更为方便和隐蔽，这对于个人、企业和政府都存在着不小的隐患.传统的对抗方式有背景噪声屏蔽和电磁波屏蔽，但都有其局限性.前者通过播放大音量噪声覆盖对话声音，但这会影响对话的正常进行；后者发射大功率电磁波屏蔽录音设备，但其屏蔽距离与效果都十分有限.针对上述问题，本文提出一种基于声学参量阵理论的超声波防录音屏的方案，可以对录音窃听进行有效屏蔽，同时不妨碍正常对话.根据声学参量阵理论，多个高频的超声波经过非线性系统，会因为非线性作用产生低频声音信号.根据这一原理，首先生成低频宽带噪声信号，然后进行BASK调制将其调制到高频载波上，进行功率放大后由换能器发射向目标录音设备.实验测试结果表明对iPhone6S、华为P10、P20、荣耀9等智能手机的录音功能都可以实现有效屏蔽，最大屏蔽距离1~3 m不等.由于屏蔽原理的普适性，本文的方案可以屏蔽目前大多数型号的智能手机、录音笔等带录音功能的终端. 

Ultrasonic Anti-Recording Shielding Scheme Based on Acoustic Parametric Array

With the rapid development of smart devices, some recording devices such as smart phones, recording pens and other means are more convenient and hidden to steal information, causing a great hidden trouble for individuals, enterprises and the government. The traditional countermeasures, background noise shielding and electromagnetic wave shielding, show their limitations. Playing loud noise to overwrite the conversation, the background noise shielding interferes with the normal progress of the conversation. Emitting high-power electromagnetic wave to shield the recording equipment, the electromagnetic wave shielding can only provide a limited shielding distance and effect. To solve the problems, a scheme of ultrasonic anti-recording screen was proposed based on acoustic parametric array theory to effectively shield the eavesdropping without the influence on the normal conversation. According to the acoustic parametric array theory, multiple high frequency ultrasonic waves were arranged to pass through a nonlinear system to produce low frequency acoustic signals under the nonlinear effect. According to this principle, the low-frequency wideband noise signal was generated at first, and then BASK modulation was carried out to modulate it to the high-frequency carrier. After power amplification, the noise signal was transmitted to the target recording device by transducer array. Experimental results show that recording functions of iPhone6s, Huawei p10, Huawei glory 9 and other smart phones can be effectively blocked with the maximum shielding distance ranging from 1~3 meter. Due to the universality of shielding principle, the proposed scheme can shield the terminals with recording function such as most models of smart phones and recording pens.