2005 Elantra Strange Noise

I’m driving Hyundai Elantra 2005 (manual transmission). When the car slows down (no gas pedal, no brake), it makes metallic noise on the right side. It mostly happens when RPM is between 1,500-2,000. When I press the clutch pedal, the noise disappears immediately.
I brought the car to a local mechanic once, but he could not figure it out. Any suggestions? Thank you.

Two guesses:

  1. Loose heat shield on the exhaust system–these often have a resonant vibration at a particular engine speed.
  2. Throwout bearings on the clutch are wearing out

Thanks!