You are only looking at the energy in the noise itself. But to make that noise there is a ton of wasted energy in vibration, friction from gears, etc.

Noise is a symptom of "slop" in an engine. It might be unavoidable, but it's still a symptom of wasted energy.

Oh, definitely. Noise is often a symptom of wasted energy in a mechanical process.

And even producing noise with a speaker is rather inefficient. You need hundreds of Watt input for single digit Watt output in the interesting frequencies.