explain how you make something quiet in a "narrow band" around things that are so sensitive that it was claimed that "if you integrated all of the signal power

explain how you make something quiet in a "narrow band" around things that are so sensitive that it was claimed that "if you integrated all of the signal power received by the antennas, it's less than the energy used by a flea to jump". not just at any given moment. In the career of whoever said that, the total power was that miniscule.