Just tried it and it worked perfectly!
This little adapter does exactly what it is supposed to do on my GoPro Hero 3. It silences the camera's onboard mic and connects my external mic. In this case, the external mic is my headset via an intercom system. It gets rid of the wind and engine noise so we can hear the conversation between myself and my passenger... wonderful.
"NO SOUND" ~ does *NOT* work with GoPro HERO4 Silver