I know we can't hear frequencies below 15 or 16 Hz, but I have seen companies that sell sub-woofers and woofers with responses that go up to 3 or 5 Hz. What is that for?
In fact, we cannot hear frequencies below about 15 Hz, but we can feel it. This is what happens with the sound of explosions, collapses, earthquakes, these vibrations, when reproduced with great power, are felt as vibrations in our body, in the chair and in the objects we hold. For this reason, even if we cannot hear, the sound systems of home theaters, cinemas and other places where realism is desired use speakers capable of reproducing these very low (sub-sonic) frequencies.
