abilitytesting audiology audiometry child childhood congresses correctionofhearingimpairment deaf deafchildren education educationaltechnology familyrelationships hearingdisorders hearingdisordersinchildren hearingdisordersininfants hearingimpaired hv2391l2871987 hörstörung infant ininfancy ininfancyandchildhood kind language languagedevelopment languagetests mainstreamingineducation meansofcommunication methods parenting parentsofdeafchildren rehabilitation rehabilitationofhearingimpaired special speech therapy unitedstates voice wv270a9161977