"Act the siren" is a colloquialism that means to make a lot of noise or disturbance. If you're looking for synonyms for this phrase, consider using words that denote making a ruckus, such as "make a commotion," "cause a stir," "raise a clamor," or "foment a disturbance." You might also use phrases like "be loud and boisterous," "make a scene," or "create havoc." Other words to consider include "disrupt," "agitate," "disturb," or "provoke." No matter which words you choose, you'll convey the same meaning of making noise and creating a disturbance.