No, the audience is a collective noun which refers to all the people present, so '4000 audiences' implies 4000 separate groups of people. ''There were 4000 *in the audience* at the concert'' is what you are probably trying to say.

Hey there, Audience is a plural word which stands for a group of people. You could say "There where 4000 people in the AUDIENCE at the concert." "4000 audiences" would mean there are 4000 separate groups. This would not be correct.