I'm experienced with Raspberry Pi based applications. I'd use arecord and aplay (or other utils, I'm quite flexible with software choices) and netcat (nc) for transferring data over the network. If so desired (WiFi or other causes of slow network connection over two Pi's), audio can be compressed with opus on-the-fly. My design will provide sub-100ms delay and very good sound quality. If desired, I can make it a two-way system (walkie-talkie like).
I should be able to finish the project in around two to three days.