  Fast external noise, which gives fluctuation into the beam orbit, is
discussed in connection with beam-beam effects. Phase noise from crab cavities
and detection devices (position monitor) and kicker noise from the bunch by
bunch feedback system are the sources. Beam-beam collisions with fast orbit
fluctuations with turn by turn or multi-turn correlations, cause emittance
growth and luminosity degradation. We discuss the tolerance of the noise
amplitude for LHC and HL-LHC.
