Chrome Version       : 59.0.3071.86 (Developer Build) built on Debian 9.0
URLs (if applicable) :
OS version               : Debian 9.1 (64-bit)
Network (such as Cable/DSL/Dial up etc): Cable
Audio/Video format (if applicable): WebM
Special chrome flags (if applicable):

Behavior in Safari (if known): doesn't work
Behavior in Firefox (if known): works

Video issue, Audio issue, both, neither? both (see below)

Flash or HTML5?  HTML5

If the browser or renderer crashed (“Aw, Snap”), please add any crash
IDs from chrome://crashes  (possibly after enabling crash reporting per
http://support.google.com/chrome/bin/answer.py?hl=en&answer=96817)

What steps will reproduce the problem?
(1) visit https://simpl.info/mr
(2) attempt demo
(3) note that recording has no sound

What is the expected result? recording has sound

What is the actual result? no sound

Any additional information (anything else which may help us debug the
issue)?

First noticed this issue with my own MediaRecorder software. Confirmed no audio in https://simpl.info/mr, linked from https://www.chromestatus.com/feature/5929649028726784, which I assume is canonical. Furthermore, that demo (and unfortunately my own software) can't even record video on OSX. This was all working fine quite recently.

Please attach the HTML5/JavaScript code or audio/video files as well as
screenshot and/or videos (if applicable)