Hi @dindale, Thanks for reaching out and welcome to the community. Thanks for bringing this up and we understand where you're coming from. Regarding this issue. I’ll ask you to submit a diagnostic report for us to investigate further what could be causing this issue. You may reply to the thread with the confirmation number to assist you with this issue. I’ll also ask if you can take a video once the issue reoccurs so that we can further assist with this concern. 

Let us know how you get on with the advice above.

We're here to answer any further questions you have.

I’ve just had this happen to me on my first day of use of my Sonos Arc. @dindale did you receive a response from Sonos on this?

Same thing happened to me on my first day after setting up. Was watching tv for about 10 minutes then a crazy loud alarm siren started. Had to unplug the main power cord and then a solid red LED showed up after powering back on. Basically is unusable now.. 

Did you submit a diagnostic report, as the Sonos rep above asked, so they can investigate further?

I couldn't as the only way to stop the sound was to unplug the Arc, which would mean any diagnostic information is lost once you power up again. Believe me, you wouldn't want to sit through the sound for long enough to run diagnostics. I had bought mine from a 3rd party supplier, I returned it to them after it happened on a 2nd occasion and swapped it for a new one  which has been fine. They set the faulty unit up in their shop to check it wasn't something else in my set up causing the issue and sure enough the issue reoccured within 24 hours and scared the crap out of the guys working there!

Had to sit through a lengthy call and now Sonos is sending a new replacement unit. Have a one SL that never connects also. Not sure this company and their app are all they are cracked up to be. App totally sucks

I’ve got various bits of Sonos kit around the house and have had for years. The Arc is the only one I’ve had any problems with and so far the replacement unit has been fine. Some of the apps integration with other services like Spotify is a bit flakey and I’m not that impressed with Sonos Radio. What is it you don’t like about it?

The app does not recognize my products, and searching for music is a mess. We use spotify.

I've had the same loud piercing sound from my new Arc happen twice within 2 hours of setting it up.  It's shockingly loud and there's no way I'd have time to send a report without doing damage to my ears. My ears were ringing for the rest of the night after the second time. Direction needed.

According to Sonos, the diagnostic log holds 10 to 15 minutes of data, depending, I would expect, on the data stream in question. But I’d certainly recommend that rather than waiting for another occurrence, you should call Sonos Support directly to discuss it.

When you speak directly to the phone folks, there are more options available for them to assist you.

If it happens to occur again, it’s possible that running a diagnostic might be able to tell them if the sound was coming from the Sonos hardware, or it was just playing something it was being handed from an external source, but I wouldn’t wait for that. 

This happened to me three times today while trying (without success) to connect my new arc and gen3 sub.  It was so sudden and so loud that I believe there may be permanent hearing damage.  Like others, I tried volume control first then had to scramble to unplug the unit with my head right next to the device.  I have had Sonos products for years and really like the sound quality, but this has certainly given me cause for concern.

Never had this issue with either Arc I own. As suggested in the post immediately before yours,I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

Jyst to add, you can contact Sonos Support via this LINK during their usual opening hours to discuss the matter with them.