A portable, wearable personal audio system which includes an acoustic sample chamber and an acoustically transparent ear insert member. A tubular member transmits the audio from the sample chamber and module to the ear canal. The ear insert stabilizes and secures the tubular member in the ear...http://www.google.com.au/patents/US5694475?utm_source=gb-gplus-sharePatent US5694475 - Acoustically transparent earphones
