The bypass capacitor between the BST pin and the SW pin squeaks
Welcome to the MPS Technical Forum. The component values seem to mostly match our typical circuits and EVB examples. What is the P/N of C10? How do the main waveforms (Vout, SW, iL, etc.) appear when the noise is present?
What good ears you have. Can you wait this one out, eventually your hearing will get worse.
Noises are really difficult to pinpoint, I would suspect the inductor before that capacitor. How does the PWM look? Is it a stable duty cycle or is there big jitter which may indicate control loop problems.