Low Frequency Modulation 1; Extremely Low Frequency Warble Tone; Regular Pulsation, Close Perspective.

Low Frequency Modulation 2; Low-mid Frequency Rumble; Dual Pulsation, Steady, Close Perspective.

Low Frequency Modulation 3; Electrical Power Surge; Oscillation, Sweeping Down, Then Pulsating; Classic Sci-fi Throw The Switch Effect, Close Perspective.

Low Frequency Modulation 4; Extremely Low Frequency Rumble With Hiss / Whine In Background; Pulsating Slowly, Then Gradually Rising In Pitch And Tempo, Close Perspective.

Metal Purr, Machine, Low Rolling, Ambient, Purring, Hum

Prowler Hoist, Machine, Electric Space Engine, Floating, Atmosphere

Underground, Machine, Distant Space Construction, Pulsing