The phenomenon has been documented in many diffrerent ways. In general it's known as ITC. "Intrumantal-Trans-Communiction." Reports from those who've experienced them report alledged phone calls from the dead. voices of the dead coming over radios are just a couple things folks report.

EVP is well documented under many experiments by well educated people. Even the Catholic church studied the EVP phenomenon. So, there are reports and examples of the disembodied or in some cases the dead reported communicating though electronics.

Look up Raudive and his research. "The ghost of 29 megacycles." By George Meeks.  

The info is out there and documented and researched experiements.