A hearing aid apparatus employs {HEAD ~ a single side band modulator} which serves to convert {TAIL ~ an audio band} of frequencies into an upper and lower side band signal 
serves to convert
A hearing aid apparatus employs { HEAD ~ a single side band modulator } which serves to convert { TAIL ~ an audio band } of frequencies into an upper and lower side band signal
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH