The applicability of this is forensics analysis it seems (but you could easily find other usecases). You can use ENF (electrical network frequency analysis) to determine if a recording is fake or not because this "fingerprint" gets recorded along with whatever you are taping. If the fingerprint of the fake recording is not the same as the fingerprint of a recording that you trust, (yes you need to have a trusted recording taken at the same time with the untrusted/analyzed one) busted !
The credit for this research goes to a Romanian forensic expert, whee :-)
Some other links: