Sub harmonics will also have very strange effects on the human nervous system. They can induce rapid alpha states, paranoia, irritation, anger, etc, without the subjects even hearing the sound...
Nikola Tesla said that he once nearly toppled a building being built in NY by way of attaching a handheld "resonator" to a steel beam. He turned it off after the construction crew began evacuating the area. He told a journalist once about a hypothetical way to crack the bloody planet in half by carefully-timed explosions in harmony with the earth's resonant frequency.