Privacy Threats of Acoustic Covert Communication among Smart Mobile Devices

<table class="figure-group"><tr class="fig-image" id="a"><td><object data="https://static-preview.hindawi.com/articles/wcmc/volume-2021/9179100/figures/9179100.fig.004a.svgz" name="9179100.fig.004a" type="image/svg+xml"></object></td></tr><tr class="fig-caption"><td><b>(a) </b>Spectrum characteristics of normal audio frequency</td></tr><tr class="fig-image" id="b"><td><object data="https://static-preview.hindawi.com/articles/wcmc/volume-2021/9179100/figures/9179100.fig.004b.svgz" name="9179100.fig.004b" type="image/svg+xml"></object></td></tr><tr class="fig-caption"><td><b>(b) </b>Spectral characteristics of high-frequency signals</td></tr><tr class="fig-image" id="c"><td><object data="https://static-preview.hindawi.com/articles/wcmc/volume-2021/9179100/figures/9179100.fig.004c.svgz" name="9179100.fig.004c" type="image/svg+xml"></object></td></tr><tr class="fig-caption"><td><b>(c) </b>Spectral characteristics of synthesized audio</td></tr></table>

<div>Comparison of spectrum characteristics between synthetic audio and normal audio.</div>

Wireless Communications and Mobile Computing

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Figure 4

Figure 4: Privacy Threats of Acoustic Covert Communication among Smart Mobile Devices 