!setopt sirenui_size

[[TC]►Frozen◄]

Did you read the text I wrote and that also has been quoted by KaraK? That answers your question.

Whether a COP is in chase or not, you must respect other chases. If you did not know, even if you are in a chase it does not give you the right to interfere the chase of someone else. Thus, disabling the sirens is not an option else you will never know when a chase is infront or not.