It has never occurred for me, in the several years I’ve been using a Sonos Roam. Makes me wonder if it is a local issue. Have you submitted a system diagnostic within 10 minutes of experiencing this problem, and called 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 Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

The issue is rare but the number of times it has occurred to other customers who have complained here tells me it is not "local". When I interacted with Sonos support when it happened the first time I submitted a diagnostics and was told to reset the unit. It had not recurred for 2 years. I assumed - silly me - that Sonos had addressed the issue as part of one of the many updates to support new products. Evidently not.

Equally evidently they never used any units that were returned as a result of customers experiencing this to duplicate the issue, never used those submitted diagnostics to find anything in common between the units that exhibited it, or otherwise tested similar components to find a solution. That in the almost three years it has been occurring. Sonos relies on the rarity of customers having their ear drums assaulted - it is, as others have described, a horribly loud noise - to ignore the issue. As with the app failures it is just more “we are Sonos and we don’t have to care; we have new products to sell.”

Same just happend to me with my Roam at 1.30am probably also waking up the neighbors. We‘ve been watching a movie and from a slightly louder scene it suddenly started into the loud hammering noise. We also threw under the pillow before we managed to turn the volume down with the app. I read somewhere it happened for them at around 15% of battery, same for me. 
 

Well this happened to me with a 3 week old Roam 2 that lives in the bathroom on a shelf, plugged into USB power.

Tonight approx 3:00am, our NYE party cleared out. My Roam 2 is in the bathroom plugged in to USB power. Music is playing quietly then….. WAAAAAAHHHHHHHHHSHSHSHSHSSHSHSHSHSHSHSHSHSHSH, full maximum white noise, unit is vibrating like it might come apart, no control. Since it was 3AM I quickly wrapped the device in a large quilt to minimize the noise to other tenents in the building, held the power down and it stopped eventually. I factory reset it and will keep it powered off until Sonos can explain what to do. There is NO WAY I can keep this speaker in my small apartment as a ticking white noise heart attack device.  What happens to my pets if I am at work or out of town and this thing goes full blare???