CC(\delta t) = \frac{\int_{t-T}^{t+T} u_i(t')u_p(t'+\delta t)dt'}{\sqrt{\int_{t-T}^{t+T} u_i^2(t')dt' \int_{t-T}^{t+T}u_p^2(t')dt'}}, CC \epsilon [-1, 1] .
where u_i is the reference measurement and u_p is the perturbed measurement.