Hi.
To add to Stewart's answer, if hardware encryption is being used, you should see some session messages telling you as much. You try running an object verification job for one or two test tapes to see if that is reported or not. Does your organization use an external Secure Key Manager appliance? It's possible that your drive keys are being managed externally, though you should still see an informational message about that in the session reports.
Regards,
Shishir