4 Royalty-Free Audio Tracks for "Cyclical"

Outdoor escalator bart station 24 + mission streets.

It is a looping metallic droning sound made by my ceiling fan as it just started and slowly the as the speed of fan increases, the sound also revs up.

Here is a gas meter on a restaurant. I managed to get a chunk without much background noise here but i do change the mic position part way through the recording. . You'll notice it gets darker, then change it back. There's enough of each to get a good loop going as i have in the past. Recorded with a zoom h4.

Adapted from the extractor fan clip to make a repetitive industrial cyclical machinery hum.