I would beep a car horn but I'd not bleep it. On broadcasts, things tend to be bleeped out rather than beeped out. They are similar in definitions but they seem to have specific uses (to me anyway)
However, to confuse things, one source says the origin of the word "bleep" (circa 1953) was "... an electronic noise," imitative. Meaning "edit a sound over a word deemed unfit for broadcast" is from 1968." The sound used to edit a word or phrase is described as... wait for it... a "beep". So, it would seem that they are joined hip and thigh insofar as this context...