Knocking noise possibly coming from the transmission

Hello, my car makes a light knocking noise, almost like a rattle when it's in first gear, second gear, and very quietly in third gear. It also makes it very, very quietly when the car is in neutral but if I push the clutch pedal all the way in, the noise goes away.

It seems to get louder if I engine brake (in second gear). Otherwise, the car runs perfectly and never slips out of gear, the clutch feels good, it doesn't slip when accelerating.

I've checked the heatshield to make sure it's not rattling, and it's not. I couldn't see anything immediately that would cause the rattle.

Here is a recording of it with the clutch in and out. It doesn't sound exactly how it sounds real life, but is close: https://vocaroo.com/112N9xU7EFq1