This invention relates to {HEAD ~ electroacoustic devices} for performing {TAIL ~ noise cancellation}, communication interfacing, sound filtering, and headphone functions for the human ear 
for performing
This invention relates to { HEAD ~ electroacoustic devices } for performing { TAIL ~ noise cancellation } , communication interfacing , sound filtering , and headphone functions for the human ear
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH