This isn’t really all that new. People were talking about “the brown note” a decade ago or longer.
Sound is a wave, and is “cancelled out” routinely in mundane applications like automotive mufflers. Light is a wave. Thought is a wave. Earthquakes, prevented or created. Tsunamis.
A brave new world, and some weird stuff is on the horizon, or already in existence.
The military applications would be endless.