I have a strange sound (similar to the default media sound called crystal) that plays inconsistently. I have a Galaxy S9 and it is all up to date with its updates. I did not have this issue before the latest update, When the sound goes off, no notifications are visible. I have turned off all notifications (DND mode) and it still sounds. I do not have NFC on and I do not keep it anywhere near a credit card. I have also turned off Bluetooth, , sync, wifi, and location...did not work. The sound seems to be controlled by the ringtone volume, not Notification, Media, System or Bixby volumes. I have deleted every single app from my phone 1 by 1 to see if I could find the culprit to no avail. I do not have Accessability/Notification reminder on. I did notice that when in airplane mode it did not do it. I have tried ever fix I could find on the internet and am now asking the people who actually may know something. I have also restarted the phone and erased the cache many times and nothing seems to help.Anybody have any type of clue? Thanks to anybody they can provide any type of assistance.