How can you sleep through the noise?

Whenever I talk to people about Mark's deer deterrent invention, the question I inevitably get is, "How do you sleep through the noise?"  I suspect that our videos make the clanging seem much louder than it actually is --- we live way out in the country where there is no street noise to drown the deterrents out, and I can barely hear them with the windows closed.  If you lived in an area with more noise pollution, you probably wouldn't hear them at all.