Often, the sounds that you hear in your dream take their cues from actual sounds happening around you (i.e. sirens, helicopters, etc.).
If this is not the case, look up the symbol that the sound could have come from (i.e. CD player, hammer, etc.). Noise can reveal a great deal about the context and subtext of the dream. Consider the feeling tone.... Strangest Dream Explanations
Dreams of a siren are a sign to pay attention; there is a red alert emergency for you to tend to. In Greek Mythology, the sirens were beautiful women who would entice sailors to crash into the rocks, so this dream could be a warning to stay alert and be aware of the temptation to be seduced into something that could have harmful consequences. See Seducer/Seductress.... Strangest Dream Explanations