Check the Audio settings in the AppleTV 4K box. Make it’s set to Auto Dolby Atmos available. I believe that’s the setting… I’m not at so I can’t verify the the exact wording the setting.

Yes, Dolby Atmos is enabled on the AppleTV Settings. When I turn Atmos off in the ATV settings I don’t have the issue at all. It only happens when Atmos is enabled and playing. I’ve verified each time its only in Atmos that causes the issue by checking in the Sonos app and Atmos was shown as playing. 

OK…so check the HDMI cable for the ATV, make sure it’s running the latest TVOS and/or reset the ATV if necessary.

Got it. I know I’m running the latest TVOS. I’ll check the cable and possibly reset the Apple TV and report back later this afternoon. 

After checking the cables and resetting the Apple TV I am still running into the same issue. 

Honestly, it sounds (sorry, pun not intended) like a switching problem in the TV set itself, not in the Apple TV or Sonos. The Sonos would be playing whatever is sent down the line from the TV. I’d be double checking for updates of the TV’s OS. 

Can you play Atmos content directly from the TV through Netflix and see if you still have the same issue. Need to rule out the TV or Apple device first. 

I’ll play some content tonight from the TV itself and see if Atmos is steady. It not extremely frequent so reproducing the issue will take some content watching. I’ll report back with my findings. 

After playing content over both Apple TV and the build in TV apps it looks like its the Apple TV that is causing the issue. I had no audio cut outs yesterday. 

With that, does anyone know of any settings to get Atmos to consistently work over ATV? 

Assuming the TV is set to passthrough, earc enabled and plugged into the correct port from the Apple TV device it should be fine. Did you say you've tried a factory reset of the apple device ?

I reset the Apple TV again it applied an update that it didn’t do in the last reset. It seems (right now) that the Apple TV is playing the Atmos content fine. It happens intermittently so I’ll report back of the issue happens again. 

Reporting back. This issue happened again. It only happens with the Apple TV 4K. I’ve been watching Atmos content through the TV apps and its worked perfectly. Not sure what the issue is with the ATV and its a little annoying to switch back and fourth but at least I’m getting the full benefit of the Arc now. 

If anyone has had the same issue and they’ve fixed it please let me know. 

I experienced this very issue last night – nearly soiled myself thinking that I’d blown a driver.

Sonos Arc (with 2 One surrounds and a 2nd gen sub) connected to an Apple TV 4K (2nd gen) and a Sony XH92 – config not changed in over a year since purchasing last November.

Watching Shang-Chi on Disney+ via the Apple TV, no less than 4 interruptions. Fixed by backing out and entering again, or disabling Atmos entirely. 
 

I get the feeling it's an encoding problem from tvOS – this is the first Atmos movie we've watched since upgrading to tvOS 15.  We did upgrade the TV to Sony’s latest Android 10 firmware recently, but that has yet to be troubleshot. 
 

Next steps are to try for me:

Atmos content from Disney+ via aTV

Atmos content from other sources via aTV

Atmos content from Disney+ via the native TV app

See if the issue is Atmos itself with the TV/Sonos, or the Apple TV.

Apologies if you already mentioned it but can't find it if you did – what source were you playing from (on the Apple TV)?

Just tried running the same movie through the Disney+ app for Android TV built into the Sony TV itself. No issues for the first hour. Happened twice until this point.

I’ve been experiencing the exact same issue for the past month. AppleTV 4K (2nd generation), television is Sony X900H, and the Arc. When playing Atmos content I will get a loud pop then all sound cuts out. I have tried every setting imaginable and the only thing I can do is turn off Atmos content on the Apple TV.

I have the Arc connected to two One SLs and the 3rd generation Sub as well.

I’ve experienced this twice, both while watching Dolby Atmos content on Apple TV like movie rentals. Just happened again today. Loud pop, no audio from ARC until I back out and play the content again.

LG C1 TV, eARC, passthrough

Just to troubleshoot, what sources is everyone using? Disney+, Netflix, Apple TV+, or a mix if various?

It seems that this issue seems common amongst Apple TV and Xbox users; seemingly with Sony and LG TV sets.

What version of tvOS is everyone using? It seems that tvOS 15 has caused various audio issues not limited to this one…

I’m encountering the error on all Apple TV apps the stream content with Dolby Atmos--Netflix, Disney+, Paramount+ and Apple TV+.

I’m using tvOS 15.2 beta release.  I switched to getting beta updates on tvOS in the hopes that the audio issue would be resolved quicker.  It has not.

I was thinking about going to 15.2 to see if it would fix it, sucks to hear that the issue still exists. Hard to say if it’s an Apple issue, Sonos, or a mix of both at this point. I’d imagine that would be something for Sonos engineers to figure out and fix or report.

Quite possibly. It smells like the Arc struggles to recover after a decode failure, and that the Apple TV is having issues with the encoding. 

Just attempted to watching Atmos content on Netflix on the aTV — pop! (< 10min)
Now watching an Atmos encoded Blu-Ray via PS5 (passthrough audio), nothing yet…

Half tempted to see if I can put the aTV in DFU and load tvOS 14 back on to it…

i had ZERO problems with tvOS 14.  I also did not have an issue with 15.0.  Seems the problem started during the 15.1 push.

I've reached out to Apple Support and have a call with a senior advisor this afternoon, so we’ll see what's happening.

Unfortunately, seems the Apple TV 4K has no downgrade method due to no DFU mode  

New tvOS beta and a Sonos system update. Wonder if the issue will still occur later on.