Make sure the Digital Output Audio Format setting on the TV is set to Passthrough, not Auto. And use the HDMI cable that came with the Arc. You can also try turning off the Match Frame Rate settings on the Apple TV.

I see the same behavior on DD 5.1 over optical on a Playbar. Sources are Apple TV and TiVo. Started 1-2 months ago. Does it on both Playbars I have.

Thanks for the reply. I’ve done everything you said and the issues still persist. I’m starting to think the problem has to do with the Apple TV device. Hopefully Apple can fix it with an update. 

Unfortunately the Arc has a long-running problem with Atmos that is encoded in the Dolby MAT format which Xbox and Apple TV use. It appears that on the gen 1 Apple TV it “only” causes a dropout, while on gens 2 and 3 as well as Xbox, it causes a loud pop followed by loss of audio from the Arc.

Sonos recommends that you turn off Atmos on Apple TV until they fix it. But this has been going on for more than a year so we don’t know if they will fix it.

Come to the big thread and contribute your experience: https://en.community.sonos.com/home-theater-229129/sonos-arc-loud-pop-then-audio-loss-6852340

I have had the same problem. Playing through Samsung tv and Xbox. No loud pop, just random single second drop in audio. The problem is present only when dolby atmos compatibility is selected on TV. 

The sonos rep I spoke to today just told me to turn off atmos, because apparently it's a known issue with sonos and other sound bars. 

So... the Arc which touts dolby atmos, cannot play dolby atmos!!

I have had no issues since turning off dolby atmos, and playing dolby 5.1.

Based on this the issue appears to be with your (unspecified) TV or the Xbox.

No.

I have the same problem, Apple TV, arc, sub and soon era300 (moving from one’s) and not being able to play atoms makes the system kind of missing it’s purpose Problem has been ongoing over a year and I have read all the threads and done all the suggestions but the only solution is to turn off Dolby Atmos to not get the dropouts. 

I had a similar issue: after extensive contact with Sonos Support I got the request to disconnect the sub from my 5.1 setup.

(I not only had sound hiccups but in the app I could also see that the signal was not true 5.1 (app said something like stereo-PCM))

This resolved the problem, and soon after I added the sub again to my 5.1 setup all worked well.

my setup: Playbar (Arc as of writing) + sub + 2 Play:3 surrounds

On my Apple TV 4K (3rd generation) there is no loud pop, but just an Audio interruption. See more here: