I wanted to stop by and see how I could help.
Thanks for the assistance, @David_K.
@Califsydney, I know it has been a while, but I wanted to ensure that everything is covered here.
How's your Nest Protect doing now? Were you able to check the link shared by David King? The link will explain the sound that you're getting from your device.
Please let us know if you have any other questions or concerns.
Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.
Thanks for the help here, Mark.