There is a million apps that let you voip to random strangers and this is just a proof of concept, doing the same with https://github.com/nostr-protocol/nostr.
It uses https://github.com/fiatjaf/nostr-tools and 90 lines of custom code to provide a simple multi party voice chat client relying on nostr relays.
Those relays currently are almost all providing the "pipes" for free to store and forward messages. This tool here opts out from storing relatively big messages. In fact the messages are probably too big for most relays but relay.nostr.info for now does forward bigger messages for ephemeral messages.
This software can be used under the MIT license.
This software can be tried out here.
Please be aware that as of now, the connection randomly breaks a lot and reconnects are delayed more with every disconnect, so for your test, hit reload if you notice a lost connection.
Warning: This tool publishes your audio "to the world" with no encryption.