Temporal cues and the effect of their enhancement on speech perception in older adults——A scoping review

Temporalenvelopeisalowfrequencyamplitudemodulationconveyingsegmentalandsuprasegmentalinformationduringspeechperception.Unfortunately,weseldomfindourselvesincompletelyquietlisteningenvironmentsandnoise,commonlyfoundinthesurroundingenvironment,obscuresboththefinestructurecuesandpartlythetemporalenvelopecuesinspeech.Availabletemporalcontentofspeechemanatingfromnoiseisoftenenoughtoconveyrequiredinformationinnormalhearingindividuals.However,thecaseisdifferentinolderadults(withandwithouthearingloss)wholacksuchcapabilitiesduetotheimpairmentintemporalprocessing.Thiscallsattentionofaresearchertodelineatetheimportanceoftemporalenhancementofspeechinimprovingspeechperception.Therearemanytemporalenvelopestrategiesavailableintheliterature,buteachonehasitsownlacunae.Anenvelopeenhancementbyadeepbandmodulation(DBM)isfoundtobebeneficialforthoseindividualswhohavehadatemporalprocessingimpairment.Thereasoncouldbeattributedtothe15dBenhancementinthetemporalenvelopebandwidthbetween3and30Hz,extractedfromeachchannel,whichsignificantlyincreasesthemodulationdepthsuchthatmaskingofaconsonantbyavowelisminimized.Additionally,outputofdeepbandmodulatedspeechisrescaledsuchthatitsdurationincreasesanditprovidesrelativelyeasyaccesstothewordofthelexicon.Thus,inthenearfuture,withmoreexperimentsrelatedtoDBMalgorithm,itcanbeutilizedintherehabilitativedevicestolessentheimpactofthetemporalprocessingimpairment.