That is a recognised method but it does have it's own failings. Certainly in server rooms although it seems noisy to us there are patterns that can still be generated.

Another similar method is to take static from radio waves. While random it's unfortunately hackable by someone who has a radio transmitter and can get close enough to your antenna (the same can be done with the microphone).

I worked at a poker startup and sourcing random numbers is both a political and mathematical nightmare.

Add another noisemaker with a chaotic component, like a Pacinko ball game with an automatic ball feed. Hashing the output will obliterate the patterns.

Why not add a small amount of radioactive material and measure decays?