How to interpret Low Pearson correlation coefficient between stable signals and high Pearson correlation coefficient between unstable signals?
&quot;How can we determine the strength of association based on the Pearson correlation ?
Briefly speaking, Pearson  (linear) correlation (r ) is not to be interpreted the way you interpret . It simply tells the linear (constant) relationship  between two variables. It does not tell anything  about the causal relation between two variables. It is association measure based on Covariance. Another measure- is called Pearson (sample) correlation coefficient measure which is based on distance. This measure reflects a cause and effect relationship.