  We consider the behavior of fluctuations near the sonic horizon and the role
of the nonlocality of interaction (nonlinearity) on their regularization. The
nonlocality dominates if its characteristic length scale is larger than the
regularization length. The influence of nonlocality may be important in the
current experiments on the transonic flow in Kerr nonlinear media. Experimental
conditions, under which the observation of straddled fluctuations can be
observed, are discussed.
