Stockman Stand pipe sounds like slurping cup

[grubsnaek]

my stockman standpipes that i made sound like and empty cup when someone drinks through a straw. that slurping sound. like and empty McDonalds cup.
whats wrong, how can i fix it.

 

[jonk520c]

what size holes do you have drilled in the top.
mine used to be really loud but I made the holes a little bigger and if quited it allot.

 

[grubsnaek]

i might be past point of no return. my boy drilled the holes with a 5/16. to big to fit the air tub in.

 

[grubsnaek]

should the air holes be bigger or smaller in general size.