Mystery boom in Sacramento
© CBS13 Sacramento
A neighbourhood is both confused and frightened due to a large number of unexplained boom noises heard at night.

Residents of Fair Oaks in northeast Sacramento, in the US state of California, can't explain why they're hearing the noises.

A number of them wrote about the concerns on Facebook after hearing booms since mid-February.

"I've heard the booms occasionally and thought I was just hearing things," one woman wrote.

"Wondering if it's a weather phenomenon or overhead aircraft.

One man wrote he hears them anywhere between 8pm and 12am, sometimes even multiple times a night.

A number of theories have been floated.

One woman suggested it could be an acetylene bomb which are made with gas and balloons.

Other suggestions are gunfire, illegal fireworks or exhaust pipes.

One man compared the sound of the booms to that of two Space X rockets and included video of them landing in comparison.

The booms are loud enough to set off car alarms, CBS Sacramento reported.

"It rattles windows, it sounds like a firework going off in my backyard," resident Dallis Stumpf told the station.

She added the sounds wake her two-year-old daughter and freak her out. Another resident described the sound as like 'gunfire with a bass drum'.

Police told CBS Sacramento investigators are confident the sounds are being caused by powerful, illegal fireworks.

In June last year, residents in Cairns claimed to have heard a series of explosions at about 11pm.

In November, Darwin residents who were already dealing with wind gusts and lightning on a Wednesday morning when they were woken by boom noises.