The Towamencin Supervisors want to keep a lid on loud partys and other sources of late night racket.   They have approved a noise ordinance for advertisement.   It could be back before the supervisors for a vote next month.   Towamencin officials say some measures are currently in place to keep the peace but after a recent incident involving a complaint about noise in a residential neighborhood they realized there is nothing on the books to handle that sort of situation.   The township already has a device that police officers could use to measure noise levels.   Two more might be needed though if the ordinance is approved.