Nothing’s more nap-inducing than the soothing tones of NPR’s broadcasters. So in a roundabout way, it makes sense to take a relaxing cruise with the stars of notable public-radio shows. Journalists like Michele Norris and David Greene will hold panel discussions and Q&A sessions on topics ranging from politics to pop culture aboard Regent’s Seven Seas Voyager ship. Fittingly, for the serious-minded NPR listener, Public Radio at Sea is no tropical cruise; passengers board in Beijing and stop by Shanghai, along with Thailand and Vietnam.