Should I be worried?

I drive a 2007 Hyundai Sonata GLS (2.4) and recently I started hearing an unnatural raspy, metallic sound from the engine/transmission. The sound isn’t noticeable on some drives, but on others, it is very obvious. The engine/transmission will sound normal until between 2,000-3,000 RPM. So when I accelerate through the rev range, i’ll hear it once I hit 2,000-3,000 RPM. But as soon as the car shifts up to a new gear, the engine sound returns to normal. The engine is naturally quiet, but as soon as it hits the problematic “sweet spot”, the engine note switches from vague and muted to a sort of scream. It’s not just louder. Its a different pitch entirely. Raspy and metallic. Could this be an issue with perhaps the timing belts?