Dinosauria vocalizations

[StephanPickering@cs.com]

Zoological research since I.D. Duncan's paper of  1978 has shown idiopathic laryngeal hemiplegia afflicts equine taxa, applied generally to the longest nerve in a horse's neck, the recurrent laryngeal nerve. The hemiplegia arises when the RLN is compressed and damaged as it goes around the aortic arch, axonal degeneration often seen. Earlier, in 1970, other researchers (notably J.R. Rooney) proposed that long-necked horses during bodily movement could stretch the RLN causing nerve damage and vascular deficiencies. The latter was also found during growth, as the cervical series became more elongate (causing sinistral laryngeal hemiplegia, as documented by R. Berg in 1992).
What about longer-neck taxa? Among giraffe, larynges are actually smaller than the lighter weight horses, and the giraffe also have no laryngeal ventricles or vocal folds. In other words, although capable to making some sounds, the giraffe is functionally voice-less, as it were. D.E. Harrison's laboratory work in 1981 on fiber size frequencies of recurrent laryngeal nerves of the giraffe demonstrates that, despite extraordinary length, the RLNs of giraffe are quite healthy, idiopathic laryngeal hemiplegia being unknown in spite of the taxon's moving neck during locomotion, the neck's rapid growth after birth. The axons of basal motor neurons to the deepest laryngeal muscles are elongate.
Could it be that sauropods were silent? The giraffe compensates for muteness with heightened visual acuity, the elephant (another taxon in which idiopathic laryngeal hemiplegia is quite rare) uses a combination of trunk "honking" and infrasonic sounds. One wonders if anyone has examined well-preserved sauropod skulls for any osteological evidence of air-chambers capable of manufacturing infrasonic sound?