Read it: http://www.melhuish.org/audio/horn.htm
The sound moves air back and forth, right ?
How much does the air move back and forth ? The anwer depends on many things.
In a horn, slight air movements in the throat can carry waves with very much power. In the way to the mouth, this waves gradually move more air and the power is distributed.
For the sound energy to reach our years, it needs to move the most air possible. Withought a horn or a port, the moving air won't be greater than the driver's excursion multiplied by it's cone area. With horns and ports, the moving air can be much more than this.
The lower the frequency, the more air moving is needed. The lower the frequency, the most it seems powerfull in my opinion.
We CAN hear below 20 hz, but we can't distinguish 20 Hz from 15 Hz or 10 Hz. We hear through small hairs inside our ears. If the waves are too long, the small hairs get laid for long periods. While they are laid, we don't hear, but as the waves go back and forth, we hear that sound is playing, but we hear it as if it was 20 Hz even if it's lower than 20 Hz.
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