I hear sirens while we make love
Loud as hell, but they don't know
They're nowhere near us

from Jay Z (Ft. Beyoncé) – Part II (On The Run) Lyrics on Rap Genius

Meaning

He hears sirens which could be both sirens inside his own head, being used in the common sense “sirens started going off when i noticed…”. telling him this is unlike him or, it could also be the sirens of people trying to break them up or tell them its wrong. In this story he is also the bad guy so its possible the “good guys” the boys in blue are trying to stop him from taking the good girl

Remember the beginning of “21 Questions” where both lovers were “in their zone” until the police sirens came?

Sirens symbolize the past: the paranoia of the past to be specific, or the paranoia of the Bonnie & Clyde “bad,” “while we make love,” even during our most pleasurable moments.

To help improve the meaning of these lyrics, visit “Part II (On The Run)” by Jay Z (Ft. Beyoncé) Lyrics and leave a comment on the lyrics box