Determining Damping Ratio for Spring-Damper System

[eolceroglu]

Hi, my question is about determining the damping ratio for the upper spring-damper part of the system given in the link. Is it still r2/(2*sqrt(k2*m2)) or something equivalent should be determined?
http://img217.imageshack.us/img217/3148/sprdampmass.png
Thank you!

 

[SystemTheory]

Please be more specific. I think the only damping constant is r2 and the time constant is either a simple ratio or product of k2 and r2.