I'm not an acoustical engineer but my understanding is that noise canceling devices are usually passive - think of the oddly shaped foam panels you see in recor

I'm not an acoustical engineer but my understanding is that noise canceling devices are usually passive - think of the oddly shaped foam panels you see in recording studios: https://www.google.com/search?q=anechoic+chamber&source=lnms&tbm=isch&sa=X&ei=TQ4aVcnfLcmWgwSEn4TYDg&ved=0CAcQ_AUoAQ&biw=947&bih=975#tbm=isch&q=recording+studio+acoustic+treatment https://www.google.com/search?q=anechoic+chamber&source=lnms... Or, in an extreme example, the ones you see in anechoic chambers: https://www.google.com/search?q=anechoic+chamber&source=lnms&tbm=isch&sa=X&ei=TQ4aVcnfLcmWgwSEn4TYDg&ved=0CAcQ_AUoAQ&biw=947&bih=975 https://www.google.com/search?q=anechoic+chamber&source=lnms... The foam devices serve to both absorb sound energy, and to scatter the remaining sound energy at a variety of angles, where much of it will collide with other reflected sound waves and cancel out. I needed some acoustic foam for a small project at home and found this place. They seemed pretty affordable (and had lots of colors) compared to other places, though I'm far from an expert and I was only buying ~$40 of foam so I didn't exactly spent too much time comparison shopping: http://www.foambymail.com/acoustical-foam-products.html http://www.foambymail.com/acoustical-foam-products.html