Make an audio recording. Also use this app:
https://apps.apple.com/us/app/vibrat...o/id1089589547
It will isolate the exact frequency of the sound which can help determine the source. It reports the g-force the phone experiences and by moving the phone around to different places you can pinpoint the source.
Last year somebody traced a similar sound to the thrust bushing bolt bring loose and another traced it to the bearing at the top of the strut tower.