Can also be ceramic capacitors, specifically type 2 dielectric, which are somewhat piezoelectric.
Actually, most capacitors are electrostrictive at least (meaning, they expand in response to an electric field -- distinction is, electrostriction is proportional to E^2 and thus unsigned, doesn't matter the polarity or direction of E; while piezoelectricity is proportional and signed), though you may need a large voltage swing to see it.
Inductors are the most common noise source, because they see the most ripple in a converter. The effect responsible is, guess what: magnetostriction.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
(There is such a thing as "piezomagnetism" as well, but it's actually rather rare.)
Tim