工业电机低频循环

Seamless looping quiet industrial machine hum, one second that loops perfectly: a steady 120 Hz motor drone with a faint 600 Hz whine and a very soft irregular metallic tick. Dry, close, unobtrusive. No reverb, no musical pitch, no melody, no fade at the loop point. Keep the peak below -3 dBFS, no clipping or distortion.