Two ways this is useful: - It is possible that the airgapped system still has a publicly viewable screen displaying harmless information. But you use this tech

Two ways this is useful: - It is possible that the airgapped system still has a publicly viewable screen displaying harmless information. But you use this technique to leak secret information from the system. - If the authors established that 2m is the maximum distance that you can reliably leak information this way, then that is in principle useful information for someone designing the security system. No audio recording software allowed within 2m of the screen!