Authority through knowledge (of FLOSS and GNU/Linux)
If you're looking for encrypted voice chat, Mumble might be a solution. It features high-quality, low latency Voice over IP (VoIP) for communities up to 100 users. There's no public service on my behalf. Take a look at the official public serverlist.
At the server-side you need to install and setup murmur according to mumble's wiki article and the Mumble — UberLab 7 documentation.
Mumble's server software murmur logs per-server entries to an internal database and show IP addresses in user status window for privileged users by default. For privacy these settings must be disabled by specifying:
in configuration file
By default, murmur is quite verbose about service quality (user counts, bandwidth) and announcements via bonjour as well as technical server details about OS and software version. Edit the following configuration values to change this behaviour:
allowping=false bonjour=false sendversion=false