The second input transducer supplies an electrical signal corresponding to the residual noise to {HEAD ~ the control circuitry} to cancel {TAIL ~ the residual noise} 
The second input transducer supplies an electrical signal corresponding to the residual noise to { HEAD ~ the control circuitry } to cancel { TAIL ~ the residual noise }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL