Some onomatapeia that an English speaker would probably understand:
Eating something crispy or crunchy:
"CRUNCH CRUNCH"
Eating things generally:
"MUNCH MUNCH"
"NOM NOM"
"OM NOM NOM"
Farting:
"PARP!"
"TOOT!"
"POOT!"
Wind blowing:
"WOOSH!"
"SWOOSH!"
"WOOOOO!"
(add as many Os as you like)
Punches, kicks, hits and impacts:
"SMACK!"
"WHACK!"
"WHAP!"
"WHAM!"
"POW!"
"BIFF!"
"BAM!"
Explosions:
"BOOM!"
"KA-BOOM!"
guns:
"BLAM!"
"BANG!"