aged aging audiology auditoryperception child cochlea cochlearimplantation cochlearimplants communicationbarriers correctionofhearingimpairment culturallycompetentcare deafness diagnosis dizziness ear hearing hearingaids hearingdisorders hearingdisordersinchildren hispanicamericans infant innervation languagedisorders methods physiology presbycusis preschool rehabilitation speechdisorders surgery therapy tinnitus wv270 wv270b195d1984