[javra]

I think volume is the key here... The hackers induced harmonics in the audible range but at a volume that was only perceivable by the microphone and not by the bystanders. So to me it seems that it's possible to prevent this by require a higher threshold of volume to activate.

[EGreg]

I am just worried the hackers will then make sounds that sound like noise, but at least it will be characteristic and alert the person (maybe).