Do you hear that sound? It’s 65 million years ago and there’s a dinosaur calling out through the wilds. But it’s not a roar. Instead new research says that sound would probably be better described as a “coo” or a “mumble.” Researchers from the University of Texas did a comprehensive review of the vocal organs of birds and the kinds of sounds they made. The results, they say, suggest that many dinosaurs were far more likely to vocalize with a closed-mouth—perhaps, a disapproving “hmm” or a more pensive “umm”—than with a full-throated roar.