The Watershed areas of Florida have been where I have recorded some of my best howls at night. It is always when you can hear mechanical sounds in the background that something is out and aobut. The reason may be because these pumps are in the swamp areas where they live. The ecosystem is right for a large primate.
This video has an audio taken a couple years ago where you can hear the pumps, the tree tearing from the ground, the howls of multiple animals. Just be aware of how easy our senses (especially hearing) can be fooled.