I don't think they have they audio tapes yet. They have suspended microphones in the area but last I heard no confirmed Ivory calls.
It the birds are out there, then they should be able to hear them, and they should be able to record them.
Read the paper that was linked in post #42. It states that researchers have recorded drumming of Ivorybilled Peckers. It also has (blurry) stills from the video with an analysis.