UltrasonicWhisper: Ultrasound Can Generate Audible Sound in Your Hearable

Recent studies have shown that ultrasound can be used for voice input to microphones such as smart speakers by taking advantage of the nonlinearity of the microphones. A similar attack on the hearing of a user wearing a hearable with an outside microphone is also possible. Specifically, information modulated by ultrasound from an attacker is demodulated into audible sound inside the hearable, and audio information can be presented to the wearer via its inner loudspeaker. This process could result in the presentation of false information disguised as instructions from the hearable and possible interference with the user's hearing. In light of those issues, this study experimentally evaluated the possibility of ultrasonic attacks on hearables. Evaluation results confirmed that mean Mel-cepstral distortion (MCD) and mean opinion score (MOS) of the demodulated sound were 7.90 and 2.53, respectively. We also confirmed that The participants followed 14.9% of the false instructions presented by ultrasound even when they were alerted to the ultrasonic attack.