Media mogul Sumner Redstone, who maintains voting control over CBS and Viacom, has resorted to communicating through an iPad preloaded with audio clips of his voice saying "yes," "no" and "f--- you."

The ailing 94-year-old is currently caught in the middle of merger talks between the two companies, with CBS close to making an all-stock offer for Viacom.

If there is a merger agreement, Redstone will likely communicate his thoughts through a combination of curt yes-or-no verbal answers backed up by the recorded responses stored on his iPad, some people who recently have met with him told The Wall Street Journal.

National Amusements did not immediately respond to CNBC's request for comment.

The all-stock bid would propose that CBS CEO Leslie Moonves would stay at the combined company for at least two years, sources told CNBC.

But uncertainty remains over whether the senior Redstone is fit to participate in the discussions, especially given his inability to speak beyond one-word sentences and grunts. A lawsuit filed in November 2015 by an ex-girlfriend challenged his competency.