Noise Promoting Headphones

I am developing a pair of headphones that will actively reproduce the external audio through the headphone speakers. This will mean that the user can continue to be aware of their audio environment while listening to their chosen audio in the headphones. This will have application to many groups including the blind and partially sighted. A full run down and up to date commentary is available on my blog - http://stevengartland.co.uk/category/tech/noise-promoting-headphones/