Might be time to set the front end up on jackstands and check the entire front end suspension. Have you recently done a front brake job? Any service to parts forward of the rear of the front wheels besides what you did before the sound was first noticed? After checking the front end for any play, come back with an update. Also, while the car is up on the jackstands, take a look at the flexdisk job to see if anything came loose. Good luck!