Voice software comes from the provided O/S like Win10 have a few voices built in but if yours have none there is nothing that can be done unless you find some or purchase voice software to do the voice narrating back.

Thanks for the reply. Part of my question was to ask if anyone knows of free speech-to-text packages that could run on that platform -- CentOS 6 with Firefox. Chrome dropped support for CentOS 6, but upgrading to CentOS 7 is not an option because this is an older laptop.