PWM Noise led driver
Piezoelectric effect in the ceramic capacitor due to the 500 Hz PWM should be your main suspect, although you can't rule out the role of the inductor.

Look at this excerpt from MPS Application Note AN021:


  The familiar PWM dimming frequency range is less than 1kHz. Due to the
  piezoelectric effect of the ceramic capacitors and the oscillation of
  wire winding coil, the discrete low frequency (relative to the WLED
  driver’s switching frequency) dimming cycles can possibly cause
  audible noise in the system.


Debug your board by gently pressing all ceramic capacitors, one at a time, with something non-conductive and anti-static. The purpose of this test is to  prevent the capacitors from vibrating. If noise ceases or greatly drops when pressing a capacitor, then you'll have found the culprit. Beware: you may found that not only one, but several capacitors contribute to the noise

Start with the output capacitor, \$C_{out}\$ P/N GRM21BR71H105KA12L. This part is a 0805 MLCC X7R. As you can see in this paper from Kemet, any multilayer ceramic capacitor (MLCC) with dielectric X7R (or any class 2/3 dielectric) can generate perceptible acoustic noise under certain circumstances:



Also note that the Murata capacitor catalog warns you that their GRMxx capacitors aren't "anti-noise" - a reference to acoustic noise generated due to piezoelectric effect:




So, which are the main options do you have to prevent this effect and its noise?


Replace the culprit with another capacitor, either a ceramic one that does not exhibit this effect, or a completely different one material-wise (electrolytic or film).
Stiffen your PCB by mechanical means in the vicinity of the culprit, in order to prevent the board from vibrating and acting as a speaker. If the inductor is the cause, this also applies.
Use a driver that can do PWM above the audible range. 


There are other options, but you may want to research them for yourself.