German computer scientists say malware could transmit sensitive data over the air. The data can be sent at high frequency over air as computer operating systems do not tightly control a programs access to the speaker. A covert acoustical mesh network can be conceived as a botnet or malnet that is accessible via nearfield audio communications. This attack cannot work at all unless your computer is compromised, says FKIE. It does not mean malware can infect your computer via sound, but it does make things much trickier. If malware that is infected by attempting to transmit data at ultrasonic frequencies it may also attempt to subvertvert a filter.”]
Source: https://grahamcluley.com/malware-air-gap-computer-sound/