Key Points
- Perth residents reported a loud noise and windows and buildings shaking just before midday on Wednesday.
- Those who heard the sound thought it was an earthquake or an explosion but authorities have said neither occurred.
- Singapore has now clarified that one of its aircraft may have been responsible
The Singaporean defence ministry has said that a large boom felt and heard across much of Perth on Wednesday "could have come" from its aircraft training off the coast of the Western Australian capital.
People in suburbs along a 35km stretch of coastline from Fremantle to Waikiki reported hearing the boom shortly before midday, and many also described buildings shaking.
The incident left many people across the city puzzled about the cause of the sound and vibrations.
Western Australian police said it was not a police incident, while a spokesperson for St John Ambulance said paramedics were not called to any matters that could explain the noise.
Singaporean Air Force issues statement
Four Republic of Singapore Air Force (RSAF) planes are training out of a nearby Royal Australian Air Force (RAAF) base, the nation's defence ministry clarified in a statement released today.
"The F-15 aircraft are flying about 70km from the coast at above 24,000 feet over sea in the designated training area. Initial findings indicate that the noise could have come from the training aircraft," the statement read.
"The loud noise was unexpected as the F-15 was far out at sea."
"The RSAF apologises for any alarm that the training activity may have caused."
The RSAF-RAAF training is running from 13 August to 6 September.
Singaporean statement backs expert opinion on sonic boom
Matt Woods from the Perth Observatory said there was a good chance a military aircraft was responsible for the noise.
He said the noise was likely a sonic boom, either from a meteor or a fighter aircraft.
"A sonic boom is when an object like a meteor or space junk or a plane flies through the sound barrier, so the sound has a certain speed, and you can actually break through it," Woods said.
While the cause of the sound and vibrations has not been definitively confirmed, Matt Woods from the Perth Observatory has said it was likely a sonic boom, which could have been the result of a fighter aircraft or a meteor. Source: Getty / yenwen
Given the day's temperature and humidity, Woods said a fighter aircraft would have had to have been travelling about 343 metres per second to break the sound barrier.
He said he had not heard any reports of a bright green flash in the sky, which would have indicated it was a meteor.
And if it was a meteor, it wasn't recorded by the observatory.
"We were completely covered by a cloud here at Perth Observatory and there was a tree being felled by a chainsaw, So we didn't hear it, we didn't see it either," Woods said.
He said objects in the sky breaking the sound barrier have the potential to break windows.
While SBS News has seen no reports of windows being broken, many people have said their windows rattled.
"That's why a lot of supersonic aircraft have restrictions around the world on where they can fly," Woods said.
"If a meteor explodes in the air, a shock wave can happen — just like — there was a meteor that we didn't even see was coming in the direction of the sun, and when it burned up in the atmosphere it exploded.
"It just got way too hot and disintegrated, and the resulting shock wave caused glass to shatter, and people had seen the flash beforehand and run to the window, thinking it was a nuclear explosion, and then got a face full of glass
"It put something like 5,000 people into hospital."
