Whats the main difference between NDT and eddy current testing?

[ramshree]

I am trying to figure out as to what is the biggest and the most likely difference between a non-distructive testing by means of acoustic sensors where by one can determine/distinguish between a good and a bad part by means of the frequency vs time graph
and
by means of eddy current.

Like what I am looking for is what are the advantages of using acoustic sensors over eddy current and in what applications, as well as what is the advantage of using eddy current over acoustic sensors and in what applications.

Even if you can tell me a source on the internet as to where I can read and learn about the differences between these two, I will really appreciate it.

Thank you.

 

[ramshree]

Sorry, I did not mean difference between NDT and Eddy current. I meant difference between RI (Resonant Inspection) and eddy current. Sorry for that and I did not know how to edit it once I posted

Thanks again.