FreeDV is a Digital Voice mode for HF radio. You can run FreeDV using a free GUI application for Windows, Linux and OSX that allows any SSB radio to be used for low bit rate digital voice. There are several reports of the new FreeDV 700D mode outperforming SSB at low SNRs. At high SNRs FreeDV 1600 sounds like FM, with no annoying analog HF radio noise.
more information and download at https://freedv.org/