It’s difficult to fully understand the type of chime you are referring to, but my first thoughts are you might be referring to the voice assistant ‘wake word chime’.

Assuming you have a voice assistant installed to the Arc, perhaps try this…

Goto ‘Settings/Services & Voice/Voice” select your voice assistants service (Alexa or Google) and goto the Arc Room where you can disable the ‘Wake Word Chime’

I’m not sure if that is the answer to what you are referring to in your post, but perhaps see if that resolves your issue.

I thought it might be that so I removed the voice assistant  and it just happened again after I did. It is strange like a notification from an app or maybe a connect or disconnect. It is random, very strange. 

Try fully powering off the Arc & surrounds for 30 seconds and back on again and see if that resolves the matter.

One other thought I’ve just had, assuming all cables are correctly seated, is that there might be other devices/peripherals connected to your TV which may have HDMI-CEC and that they are attempting to steal control from the Arc ..and the Arc is then taking back control.
 

Check any devices that are cabled to your TV and see if they have HDMI-CEC control and see if switching off that feature resolves the matter. Note, some manufacturers have different names for the HDMI-CEC standard, but you are looking for settings that control the TV (i.e. powers TV on/off or controls TV volume using its own remote).  

I will try that.

I have:

LG OLED C9 - CEC enabled.

Shield TV PRO CEC enabled.

I will try turning CEC off and see if it solves the issue.

So does the Sonos emits a chime when it interacts with a device to take control?

Thanks.

I’m not sure daxman27, but the chime you describe sounds like it might be something reconnecting?
 

If it’s not the CEC control then the next thing to look at might be the Arc’s local network connection .. I have the C9 TV too and don’t have the issue, so was thinking something is taking control of CEC and then Arc is taking back control.. it’s just a ‘suggestion’ on my part of things to perhaps try.
 

If no answers are found, by these steps, then you can go down the route of submitting a Sonos Diagnostic and asking the Sonos Staff to step in or contacting Sonos via this LINK.

Thanks for your help.

So far after I did a hard reboot, it has not happened again. If it does I will try reaching out to them.

That’s good. Hope it is fixed for you, or that you get to find the root cause.

Oh and ‘nice TV’ by the way … I love the C9.

Me too. I had a B6 and upgraded last year to the C9. The picture quality is amazing!