We may never truly know what noises dinosaurs made, but we can use several discoveries and technology to help narrow things down. For Triceratops, the most useful information comes from a 3-D Scan of its skull. By looking at the tiny inner-ear bone of Triceratops, called the cochlear duct, we can tell what frequencies it was able to hear. The cochlear duct of Triceratops is relatively short when compared with other dinosaurs, meaning they were best adapted to hear low frequencies at 290 hertz - around a middle D note on a piano. These sounds were made with the hearing range of Triceratops in mind, but amplified so you can hear them crisply and clearly. -Jonathan Begbie (Extinct Species Vocal...