The sound has been likened to that made by a jet engine, a hot air balloon or a giant blowtorch.
Some worried residents have contacted Nottinghamshire Police, who said the noise could be from machinery.
It has been heard for several weeks, with reports coming as far north as Wollaton and as far south as West Bridgford.
"For the last two mornings, I've heard a series of noises outside my house in Wollaton which sounds like a giant blowtorch," resident Hayley Compton said.
"We went outside and it was really loud, I looked up into the sky expecting either to see flames or a very close aircraft of some sort," she added, saying that the noise sounded like it was coming from somewhere in south Nottinghamshire.
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Another resident, Gemma Cann, phoned the police after hearing the noise repeatedly from about 04:30 BST on Friday.
"It sounded like a sort of explosion and then something coming out of something, like a balloon or something like that," she said.
"As I was talking to the police I said 'I can hear it now' and he said 'I can hear it too', so he could hear it from the police station."
BBC Radio Nottingham reporter Kevin Stanley heard the noise in Radford at about 07:15 BST on Saturday and again about half an hour later.
"To me it sounded like a whooshing noise which seemed to be passing from one place to another, like it was moving," he said.
A strange whooshing noise has been waking Nottingham residents in the middle of the night.