[Android Q&A, Help & Troubleshooting] @xDeepS:
I am at a loss for what else to do as for troubleshooting, for the most part I know what I am doing when it comes to tech/apps etc. However I have noticed something very strange, creepy too, in the last week and a half. Everytime I hang up a phone call a random audio clip starts playing on my phone. Sometimes the audio sounds like a recording (like the phone randomly recorded something while I was out and about and was replaying it. But I could not peg the location, so I figured its playing a recording, but it isn't from my whereabouts, still creepy), other times its random music clips, I wouldn't be surprised if this switches to inappropriate audio at this rate.

The audio seems to be cut at a 30-40 sec loop, yes it restarts itself and plays indefinitely unless:

I make a phone call, it stops. 50% of the time it resumes after the call.

I have to restart the phone 98% of the time to make it stop.

Or I hit the recent apps and click 'close all'. I'd like to specify only hitting 'close all' stops it, manually closing apps all apps from recents doesn't do the trick.

In my effort to troubleshoot I have tried to:

Close apps from the recents individually hoping it'd help me find the culprit app emitting the sounds. But I had no luck.

I downloaded Malwarebytes and have scanned my phone with it, it didn't find anything helpful regarding to this issue.

I have checked my android filesystem through the file explorer thoroughly trying to look for MP3's or any other relevant audio files.

I have gone into app info screen and force stopped almost all media apps such as spotify, youtube, instagram, fb etc any app that I may suspect to be playing audio in the background or an app I may have used recently. Force stopping it all yielded no results.

I even went into developer settings and dug into the running services, and cached processes and started killing them all one by one and it still didn't stop the audio!

I also made sure I didn't have any hidden or suppressed notifications making it so that the app playing the audio wouldn't appear in the notification panel.

The got the phone mid July, when I got it I factory reset it twice (it's just something I do with new phones). I set it up as a new phone, I am not a fan of letting Google/Samsung restore apps. I did restore the call log and messages through the Samsung backup service.

I haven't noticed any unusual drain that may have been caused by this issue. I would consider myself a power user and use my phone quite a lot through the day. I don't download random apps, most games I play are paid (fortnite/pubg being an exception) so I doubt it's some silly game throwing ads at me. I have Adhell installed and configured properly to filter out 80% of the ads on the phone. So while I could just go ahead and factory reset my phone, my curiosity would like me to get to the bottom of it. I found one more similar thread on the internet about something like this, here is the link to it. It's mostly inconclusive for the most part however the symptoms mentioned are similar to mine.

I have a feeling there is something going on at system level. I should also note the audio channel the audio is playing through is not the "Media" channel, because while this audio plays in the background, even if I play a song on Spotify or play a video on YouTube, this would continue to play on top of it. It persist even after the screen is locked! Interesting part is I can control its volume through the Media slider however.

I know this sounds like a creepypasta story but its been creeping me out the past few days. I genuinely thought someone was spying on me the first day or two before I bought into those big brother is watching conspiracy theories. But I am not located in the United States and I am sure no one is spying. But I have cleared all sensitive files from my phone just in case.

Any help or further troubleshooting ideas would be appreciated, I wish I could troubleshoot on demand too, but this happens once every five phone calls I take. So reproduction has been a pain. I hope this is the right forum to post in, I'd post in galaxy s9 forums, but I feel this is more in this forums ball park.