At 9am every morning my phone makes a notification noise. Every day. Always 9am. There is no actual notification to go with the noise. Every day.
Place your device in to Safe Mode prior to the alarm sound and see if it still happens.
If not, this would indicate a 3rd party, user, app or setting is causing the issue.
If it is not happening in Safe Mode it means that it is nothing to do with the Samsung firmware and is down to one of your own 3rd party apps or settings.
Start by going through your downloaded apps and their settings to see if you have enabled an alarm in any of them. Failing that, temporarily, disable each app, one-by-one until you discover the culprit.
Have you added or updated any 3rd party apps in the last week or so, or changed any settings?