The Nature News story on the gorilla genome includes this section relevant to the evolution of hearing in gorillas and humans:
Some of these rapid changes are puzzling: the gene LOXHD1 is involved in hearing in humans and was therefore thought to be involved in speech, but the gene shows just as much accelerated evolution in the gorilla. But we know gorillas dont talk to each other if they do theyre managing to keep it secret, says Scally.
This weakens the connection between the gene and language, says [Wolfgang] Enard. If you find this in the gorilla, this option is out of the window.
This is one of the genes that I have been working on with reference to its acceleration on the human lineage. It is a mistake to view the evolution of hearing to be directed specifically to language; instead human and gorilla lineages are both adapting to an aural environment different from ancestral hominoids. In both these lineages, there was an increase in body size and reduction in the mean frequency of vocalizations, enough to prompt adaptive changes. In humans, we have had additionally the addition of language as a communication system, which has its own auditory requirements. The connection with language is only indirect, in that human-specific changes to this and other genes provide evidence of adaptive change in the auditory system.