Your Rocket.Chat version: 0.43.0
I noticed the current voice recorder is making use of recorderworker.js which is recording dual channel non-compressed wav file. I found a folk has already wrote a js based on recorderworker and lame which provide mono mp3 recording. Shall we try to incopeate into RocketChat? as more and more user rely on voice message nowadays, wav give a high pressure on the storage system.

Here is the link for your reference:
http://audior.ec/blog/recording-mp3-using-only-html5-and-javascript-recordmp3-js/

Best, CL