Facebook has made no secret of its love for video, challenged only perhaps by its affection for bots.

The re-creation of Facebook as a video platform is well underway: Facebook Live experiments abound, it's trialling what are basically 15-second ad breaks, and now the social media behemoth is treading delicate ground; testing how users react to autoplay video in their newsfeeds. With sound.

From Tuesday local time, some Australians may notice autoplay on all types of video (including ads and Facebook Live) acting differently on their mobile app.

In one version of the test, sound plays immediately as the video begins, if you have sound enabled on your device. Another group is able to turn sound on during the test session using an icon that will sit to the bottom right of videos.

Both groups see a pop-up message informing them about how to use the controls, and sound will only play if the smartphone's volume is up. If you don't want to annoy your workmates, sound can also be turned to "always off" in Facebook settings.

"This is one of several tests we're running as we work to improve the video experience for people on Facebook."

"We're running a small test in News Feed where people can choose whether they want to watch videos with sound on from the start," a Facebook spokesperson told Mashable Australia. "For people in this test who do not want sound to play, they can switch it off in Settings or directly on the video itself.

"This is one of several tests we're running as we work to improve the video experience for people on Facebook."

It's an intriguing trial run, given Facebook's own research has found 80 percent of people react negatively when mobile video ads play loudly without warning.

By virtue of its size, even a tweak such as complicating the opt-in sound option on Facebook is potentially fraught.

You can imagine few people would be happy to have Facebook autoplay video with sound, unless they only open the social media platform in the privacy of your own home. And who does that? At work or on the bus, instant sound would surely provoke a mad scramble for headphones.

Silence has been the norm so far, on Facebook and on platforms like Twitter. According to a report from Digiday that surveyed various publishers, up to 85 percent of video views on Facebook are without sound. About 50 percent of time spent with video on Facebook is with the sound on, a Facebook spokesperson told Mashable Australia.

Many video creators now include subtitles or text to entice viewers to stick around long enough to capture that much sought after "view," without the benefit of music or dialogue.

Facebook even has an automated captioning tool for video ads. "Since most video ads in mobile feed are viewed without sound, make sure to express your message visually," it told advertisers in a statement in February.

Autoplay sound won't change things too much for publishers — they already have to be prepared for users to engage both ways.

In some cases, especially live video, having automatic sound could become a sensitive issue.

While live video of a moment such as the death of Philando Castile in Minneapolis in July at the hands of police was newsworthy footage that sparked weeks of protests, automatic sound could compound the dramatic impact for those who didn't immediately know what they were looking at. Especially if they would prefer to avoid disturbing imagery for any reason.

In any case, if Facebook starts rolling out autoplay sound globally, you'll have this small test group Down Under to thank.

UPDATE: Aug. 24, 2016, 10:27 a.m. AEST Added Facebook statement regarding time spent with video.