I heard this sound on like some text or chat room or sumthin', apple phone or sumthin'... the sound @ the very beginning when his/her neck swells like a volleyball or instant inflation of a basketball...
It's pretty interesting how many of them do this hooting in the beginning, which they do apparently to suck in some air and pump up their chest, so that it makes a bigger noise when they are beating on it.
Great moves very impressed never do this in front of the gorillas they will take it as challenge we laugh and learn and benefit from the gorillas thanks they are very smart and intelligent animals always learning something new each day from them they make good parents and grandparents god bless you guys thanks you guys rock love you guys thanks stay safe and warm out there !!! Joe