To see or use a computer scanner in your dream, represents your lack of originality and your tendency to mimic other's ideas and beliefs. Alternatively, it signifies the processing, transfer, and sharing of information. The dream may also be a metaphor that you need to "scan" and examine your options before making a decision.
To hear a police scanner in your dream, indicates an unrest within your unconscious that needs your immediate attention. Your intuition telling you that something is wrong.