I read they chirp to attract females, impress them and warn other males...here is the link...it may be wrong too though I guess, but it makes sense since the ones I bought which are all males haven't chirped I am guessing cuz there aren't any females? I know not everything online is set in stone...lol
I have good ventilation in the container cuz I read on here they don't do well in moist environment
Why Crickets Chirp