The weird vacuuming or turning on and off again noise you hear outside at night could be caused by a variety of factors. Some common possibilities include:
Street Sweeping: Many municipalities have street sweeping vehicles that clean the roads during the night to avoid traffic disruption. These vehicles often have powerful vacuum systems to pick up debris, leaves, and dirt from the streets.
Leaf Blowers: Landscapers or maintenance crews might use leaf blowers equipped with vacuum functions to clean up leaves and debris from sidewalks and public areas.
Industrial Equipment: Some industrial facilities may run vacuum systems or other equipment that create similar sounds, especially if they operate around the clock.
Garbage Trucks: Automated garbage trucks can make vacuum-like noises when picking up trash containers and compacting waste.
Utility Maintenance: Utility companies, such as water or sewage services, may use vacuum trucks to clean and maintain pipes and infrastructure.
HVAC Systems: Large commercial or industrial HVAC systems might produce sounds resembling vacuuming as they cycle on and off.
Animals: Sometimes, the sounds may be attributed to nocturnal animals foraging or engaging in other activities.
Air Conditioning Units: Certain types of air conditioning units, especially those with variable-speed compressors, can create noise that might be mistaken for vacuuming.
If the noise is persistent and disruptive, it might be helpful to investigate further to identify the exact source. You could try contacting local authorities, utility companies, or property managers to inquire about scheduled maintenance or services that might be causing the noise. Additionally, if the noise is coming from your property or neighborhood, it may be worth discussing the matter with neighbors to see if they are aware of the source.