In case you have a custom sentences.txt file, and don't want to ruin the other sounds, copy and paste the below info over the HUMAN GRUNTS section.

// HUMAN GRUNTS
HG_GREN0 hgrunt/micon1, gren1, micoff1
HG_GREN1 hgrunt/micon2, gren2, micoff1
HG_GREN2 hgrunt/micon1, gren3, micoff2
HG_GREN3 hgrunt/micon2, gren4, micoff2
HG_GREN4 hgrunt/micon1, gren5, micoff1
HG_GREN5 hgrunt/micon2, gren6, micoff1
HG_GREN6 hgrunt/micon1, shit, micoff2

// Player Alert
HG_ALERT0 hgrunt/micon2, player1, micoff2
HG_ALERT1 hgrunt/micon1, player2, micoff1
HG_ALERT2 hgrunt/micon2, player3, micoff1
HG_ALERT3 hgrunt/micon1, player4, micoff2
HG_ALERT4 hgrunt/micon2, player5, micoff2
HG_ALERT5 hgrunt/micon1, player6, micoff1
HG_ALERT6 hgrunt/micon2, player7, micoff1

// Monster Alert
HG_MONST0 hgrunt/micon1, alien1, micoff2
HG_MONST1 hgrunt/micon2, alien2, micoff2
HG_MONST2 hgrunt/micon1, alien3, micoff1
HG_MONST3 hgrunt/micon2, alien4, micoff1

// Take cover
HG_COVER0 hgrunt/micon1, cover1, micoff1
HG_COVER1 hgrunt/micon2, cover2, micoff2
HG_COVER2 hgrunt/micon1, cover3, micoff2
HG_COVER3 hgrunt/micon2, cover4, micoff1
HG_COVER4 hgrunt/micon1, cover5, micoff1
HG_COVER5 hgrunt/micon2, cover6, micoff2
HG_COVER6 hgrunt/micon1, shit, micoff2
HG_COVER7 hgrunt/micon2, gren3, micoff1

// Throw grenade
HG_THROW0 hgrunt/throw1
HG_THROW1 hgrunt/throw2
HG_THROW2 hgrunt/throw3
HG_THROW3 hgrunt/throw4
 
// Taunt
HG_TAUNT0 hgrunt/micon1, taunt1, micoff1
HG_TAUNT1 hgrunt/micon2, taunt2, micoff2
HG_TAUNT2 hgrunt/micon1, taunt3, micoff2
HG_TAUNT3 hgrunt/micon2, taunt4, micoff1
HG_TAUNT4 hgrunt/micon1, taunt5, micoff1
HG_TAUNT5 hgrunt/micon2, taunt6, micoff2

// Charge
HG_CHARGE0 hgrunt/micon1, charge1, micoff2
HG_CHARGE1 hgrunt/micon2, charge2, micoff1
HG_CHARGE2 hgrunt/micon1, charge3, micoff1
HG_CHARGE3 hgrunt/micon2, charge4, micoff2

// Idle
HG_IDLE0 hgrunt/idle1
HG_IDLE1 hgrunt/idle2
HG_IDLE2 hgrunt/idle3

HG_QUEST0 hgrunt/micon1, quest1, micoff2
HG_QUEST1 hgrunt/micon2, quest2, micoff1
HG_QUEST2 hgrunt/micon1, quest3, micoff1
HG_QUEST3 hgrunt/micon2, quest4, micoff2
HG_QUEST4 hgrunt/micon1, quest5, micoff2
HG_QUEST5 hgrunt/micon2, quest6, micoff1
HG_QUEST6 hgrunt/micon1, quest7, micoff1
HG_QUEST7 hgrunt/micon2, quest8, micoff2
HG_QUEST8 hgrunt/micon1, quest9, micoff2
HG_QUEST9 hgrunt/micon2, quest10, micoff1
HG_QUEST10 hgrunt/micon1, quest11, micoff1
HG_QUEST11 hgrunt/micon2, quest12, micoff2

HG_ANSWER0 hgrunt/micon1, answer1, micoff2
HG_ANSWER1 hgrunt/micon2, answer2, micoff1
HG_ANSWER2 hgrunt/micon1, answer3, micoff1
HG_ANSWER3 hgrunt/micon2, answer4, micoff2
HG_ANSWER4 hgrunt/micon1, answer5, micoff2
HG_ANSWER5 hgrunt/micon2, answer6, micoff1
HG_ANSWER6 hgrunt/micon1, answer7, micoff1

HG_CLEAR0 hgrunt/micon1, clear1, micoff2
HG_CLEAR1 hgrunt/micon2, clear2, micoff2
HG_CLEAR2 hgrunt/micon1, clear3, micoff1
HG_CLEAR3 hgrunt/micon2, clear4, micoff1
HG_CLEAR4 hgrunt/micon1, clear5, micoff2
HG_CLEAR5 hgrunt/micon2, clear6, micoff2
HG_CLEAR6 hgrunt/micon1, clear7, micoff1
HG_CLEAR7 hgrunt/micon2, clear8, micoff1
HG_CLEAR8 hgrunt/micon1, clear9, micoff2
HG_CLEAR9 hgrunt/micon2, clear10, micoff2
HG_CLEAR10 hgrunt/micon1, clear11, micoff1
HG_CLEAR11 hgrunt/micon2, clear12, micoff2
HG_CLEAR12 hgrunt/micon2, clear5, micoff2

HG_CHECK0 hgrunt/micon1, check1, micoff1
HG_CHECK1 hgrunt/micon1, check2, micoff1
HG_CHECK2 hgrunt/micon2, check3, micoff2
HG_CHECK3 hgrunt/micon1, check4, micoff2
HG_CHECK4 hgrunt/micon2, check5, micoff1
HG_CHECK5 hgrunt/micon1, check6, micoff1
HG_CHECK6 hgrunt/micon2, check7, micoff2
HG_CHECK7 hgrunt/micon1, check8, micoff2