Are you using an Apple TV as a streaming device?

Does this happen only when you are watching movies or shows with Dolby Atmos audio?

I have the same problem but with a Samsung TV. 

Does the led light up briefly when these dips occur?

If you have a voice assistant installed the dips in sound may be due to false awakenings.

No.

it happens with everything but more often on Dolby atmos, currently watching Liverpool vs Forest on tnt ultimate and every time the sound dips the Dolby atmos logo appears in the top right corner when the sound returns. 

No, I don’t have the voice assistant activated 

Does the logo appear on the TV screen or within the Sonos app? If its on the TV screen, it would appear its not the same issue that I have and may not be a Sonos issue at all.

When the Arc is receiving and producing Dolby Atmos contend, it is displayed about mid-screen for that room in the sonos app.

On the tv screen.

running out of ideas, don’t know what else to try 

Try these settings on the TV:

Sound Out: HDMI ARC

HDMI Input Audio Format: Bitstream

Digital Sound Out: Pass Through

eARC: On

Auto Device Detection: On

Simplink (HDMI-cec): On

Auto Power Sync: Off

I think these are all set to your recommendations.

can not find auto device detection or auto power sync.

appreciate your help 

I have the exact same issue with my LG g4. I get the Dolby vision/ Dolby atmos notification each time the audio drops out when watching Dolby atmos content (every few seconds).

Only fix I’ve found so far is unplugging and plugging in both tv and soundbar, but then the issue is back after a half hour or so. I’m past my return period otherwise would have returned it but I’m now worried the bar is faulty which Sonos don’t seem open to admitting.
 

I have spent hours on the line with support but they’ve bucketed it into ‘interference’ issues which doesn’t make sense as it’s only my fire stick nearby and I never had these issues when running my playbar with the five and subwoofer surrounds over the past 7 years. I’ve tried hardwiring the arc ultra as part of troubleshooting but no luck so far.

You feel my pain and how frustrating it is.

like you mentioned, I’ve spent hours researching to the point it’s really getting boring now, I haven’t bothered ringing Sonos as like every company they will tell you to do all the same things we’ve already tried but I agree there is definitely an issue.

As I previously mentioned I had the same issue with the previous Arc, didn’t expect to have the same issue again, I genuinely love there products and have spent a fortune but maybe it’s time for a change. 

Yeah it’s quite painful because i used to be a big Sonos fan but now I’m just complaining (and my wife is giving me the death stare each time it happens because of how much it costs) since getting the arc ultra. 

I also followed the Sonos support guys advice to try another eARC hdmi cable other than the supplied one and bought a high speed audioquest cable but it did not help at all. Exact same problems so I wouldn’t recommend forking out that way, for this specific situation at least. 
 

One weird aspect is that it doesn’t impact music over WiFi even in Dolby atmos, so I think it must be related to the TV/ bar handshake. One tip today from Sonos support was to disable my fire sticks CEC setting which I’ve done but still no luck so far.

Oh dear

like you, I have also tried a brand new cable, connected last night and it seems to tease you for some time as it doesn’t seem to do it but sure enough it does eventually return.

well if you do manage to find a fix then please let me know and likewise I will do the same.

good luck 

When I watch movies with AppleTV or via disc on my Panasonic DP-UB9000 the Dolby Atmos and/or HDR icons appear briefly in the  upper right corner of my LG’s display. However, it has nothing to do with the Arc Ultra; as the same would appear on screen when I had an Arc.

IMO what you are seeing is the hand-shake between the source (in my case AppleTV or Panasonic disc player) and your LG; as the sound still passes through it first before reaching the Arc Ultra for processing. The “dip” in sound is most likely IMO an audio transmission/pass-through error caused by your LG (assuming your HDMI cable is solidly attached on both ends)

I would look for an update to the LG firmware and/or call LG support and inform them of the issue. It may be something they are aware of and either have a solution or are working on a fix.

Sometimes “bugs” only affect a small percentage of TV’s and the fix by the manufacturer is designed specifically for those that are affected; as apposed to an en’masse deployment. The manufacturer can approach the issue either by waiting for a call from the owner; or if the TV’s  have been registered for warranty purposes, they may push out a targeted notice to those affected.

However, never say never as the issue could in fact be related to the Arc Ultra’s processing of the audio 

Not exactly… it happens at the start when switching source/ app (expected behaviour), but then it happens repeatedly during a program without switching sources. At worst every 2-3 seconds where the audio goes silent each time, at best a few times every half hour. It’s annoying and not normal expected behaviour.

All hardware updated with latest firmware and software updates. As mentioned hours on the line with Sonos support troubleshooting. The problem doesn’t seem to be with the tv since playbar worked just fine, appears to be arc specific. It’s much more frequent with Amazon fire stick 4K max content.

The Playbar was an optical connection; as opposed to HDMI for Arc Ultra. You really can’t compare the two. I’d still call LG tech support.

I didn’t mention this in my previous post; but I had an issue with one of my LG’s. I ran the update by clicking search for update and applied it; but to no avail. I finally called LG and was told the fix for my issue had to be applied in a particular manner. LG Tech Support walked me through the process over the phone. I haven’t had the issue since. I’lm just saying...

I wondered why the cable for my playbar didn’t work on my arc… just kidding.

Did you report this thread’s issue to LG? What was the fix?

I’ve already been in contact with LG support, they said it’s a Sonos issue, Sonos are blaming ‘interference’ which is vague it’s not been fun. 

Hi 

Not sure if I previously mentioned the final attempt at a fix was a new hdmi cable. 
 

well unplugged it yesterday to put everything back how it should be and noticed the sound dip from the tv speaker as I had disconnected the soundbar. 
 

decided to try the new hdmi cable in the virgin box and it still continued so did some research about sound issues with virgin and turns out there were lots. 
 

after scrolling through many I came across one who claimed to have a fix who also had a Sonos soundbar, they purchased a hdmi cec less adaptor from Amazon.

well mine arrived today and I’ve had sky sports on for nearly two hours now as that was usually the worst channel for it and the sound dip has not happened once so far so fingers crossed this was the issue and this little device stops any interference and it trying to change the source of sound.

even if you don’t have Virgin I presume the same would apply with any other source of media connected via hdmi.

I will leave a link below and eat some humble pie as it was nothing to do with the soundbar

Hope this helps https://amzn.eu/d/gIWwiXi

How’s this going for you so far? I bought and tried the same adapter on my firestick 4K max but I still get regular dropouts. The search continues…

Hi 

I had no dropouts for weeks and out of nowhere it started doing it again, which makes no sense.

I have kind of given up now, wasted so many hours.

wherever possible now I watch anything I can on the apps on the tv itself as I have no dropouts this way. 

This is quite disappointing. 
 

I hope this isn’t part of the push for customers towards the new expensive Sonos box. It might explain why Sonos don’t seem to be doing much more than telling us the issue is ‘interference’ rather than fixing any handshake issues with any other media devices.

Very, genuinely thought it was fixed.

To be honest I’d never thought of that but you may have a point.

If by some miracle anything changes or I hear of another fix I will let you know.