Has anyone heard of any success stories with Active Noise Cancelation? This is basically using the same type of technology as is used in the Bose noise cancelling headphones but in an open shop environment. A microphone picks up the noise of a machine or machines and the noise is then processed and a speaker emits a sound of equal amplitude and reverse polarity effectively canceling out the offending noise. I have heard that it can be done but can't find anyone who can sell me the equipment to do it. Any help is appreciated.