Loud Blast in South Carolina

[Duke]

Residents of South Carolina were treated to a surprise Tuesday morning as a loud boom made its presence felt and heard throughout the state.

The South Carolina Emergency Management Division received reports from Greenville, Columbia and Charleston regarding the loud noise and reached out to several agencies to figure out what was responsible.

https://www.foxweather.com/weather-news/sc-sound-investigation-what-responsible-sonic-boom

These boom stories are not all that uncommon in the conspiracy world, but this particular one caught my attention. According to the cited article, the South Carolina Emergency Management Division claims the boom was reported in Charleston, Columbia, and Greenville. If you look at the map of SC, Charleston and Greenville are on opposite sides of the state (roughly 200 miles), with Columbia close to being equidistant between them. That tells me the blast sound carried at least 100+/- miles.

The articles seemingly eliminates a number of potential sources (pre-announced military exercise, meteor, earthquake), but surprisingly omitted an obvious explanation....a supersonic a/c breaking the sound barrier. There are at least two military air bases in SC (Shaw AFB and Beaufort MCAS) that operate supersonic aircraft (F-16s/F-18s), plus any number of transient a/c that could have over flown the state. The question is how far does the sound of a sonic boom carry? I've heard lots of them, especially as a youngster, but never gave much thought as to the aircrafts' relative location/distance from me.

I'm neither an atmospheric scientist nor an acoustic physicist, but remembering sound abides by the inverse square law, I'd think a boom heard over such distances must have originated fairly high in the atmosphere and been very energetic. With given assumptions, is there any way to quantify how loud the boom was at its source?

 

[Vattic]

If it was an aircraft could it be that it flew close to each person instead of one localised bang. Isn't that how sonic booms work anyway?

 

[Ann K]

If it was an aircraft could it be that it flew close to each person instead of one localised bang. Isn't that how sonic booms work anyway?

I'd like to see a report of the time at which each location reported the boom, which could answer that question.

 

[Ann K]

They're suggesting another source:

"The South Carolina Emergency Management Division said a relief valve on a natural gas line near the Saluda Dam caused the sound. The relief valve activated to prevent a rupture of the gas line, according to the South Carolina Office of Regulatory Staff, which deals with utility providers in the state, the emergency division said."

The Saluda Dam is ten miles west of Columbia.

Another suggested cause:

While Joint Base Charleston has not yet responded to a request for comment, the base sent out an alert warning of "explosive operations" at Wharf Alpha on the Cooper River in Goose Creek. Those operations began on Monday and are expected to continue through Sunday.

https://www.live5news.com/2023/05/23/did-you-feel-or-hear-it-lowcountry-residents-report-big-boom/

The Cooper river is close to Charleston.

 

[Duke]

I'd like to see a report of the time at which each location reported the boom, which could answer that question.

Fair point. The article implies the boom was heard instantaneously across the state. I would bet the times recorded by the SCEM people, if any, were when they received the report, vice when the sound was heard by those reporting it.

 

[Ann K]

Fair point. The article implies the boom was heard instantaneously across the state. I would bet the times recorded by the SCEM people, if any, were when they received the report, vice when the sound was heard by those reporting it.

A single sound would travel, of course, at the "speed of sound", but reporting at different times could pinpoint the direction of sound travel, therefore the location.

 

[Duke]

They're suggesting another source:

"The South Carolina Emergency Management Division said a relief valve on a natural gas line near the Saluda Dam caused the sound. The relief valve activated to prevent a rupture of the gas line, according to the South Carolina Office of Regulatory Staff, which deals with utility providers in the state, the emergency division said."

The Saluda Dam is ten miles west of Columbia.

Difficult to believe the activation of a relief valve, assumed to be at ground level, could produce a blast heard +/-100 miles away in Charleston.

Another suggested cause:

While Joint Base Charleston has not yet responded to a request for comment, the base sent out an alert warning of "explosive operations" at Wharf Alpha on the Cooper River in Goose Creek. Those operations began on Monday and are expected to continue through Sunday.

https://www.live5news.com/2023/05/23/did-you-feel-or-hear-it-lowcountry-residents-report-big-boom/

The Cooper river is close to Charleston.

The original article I posted included this quote about that training operation.

But, according to a Coast Guard spokesperson, the event has them just mystified as others and did not directly link the training activity to the boom.[EX/]
https://www.foxweather.com/weather-news/sc-sound-investigation-what-responsible-sonic-boom

 

[Duke]

A single sound would travel, of course, at the "speed of sound", but reporting at different times could pinpoint the direction of sound travel, therefore the location.

Only if the calls were made immediately after the boom and were received/annotated on being taken. Someone having had to wait on hold ("Your call is very important to us.") for ten minutes would skew the data for that purpose as well.

 

[Mendel]

If it was an aircraft could it be that it flew close to each person instead of one localised bang. Isn't that how sonic booms work anyway?

Article:

A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from the supersonic object. Rather, the boom is a continuous effect that occurs while the object is travelling at supersonic speeds and affects only observers that are positioned at a point that intersects a region in the shape of a geometrical cone behind the object. As the object moves, this conical region also moves behind it and when the cone passes over the observer, they will briefly experience the "boom".

A sonic boom produced by an aircraft moving at M=2.92, calculated from the cone angle of 20 degrees. Observers hear nothing until the shock wave, on the edges of the cone, crosses their location.

Source: https://en.m.wikipedia.org/wiki/Sonic_boom

A single sound would travel, of course, at the "speed of sound", but reporting at different times could pinpoint the direction of sound travel, therefore the location.

The aircraft travels faster than the speed of sound, so accurate times could support the aircraft hypothesis. I expect it's been caught on webcams/security cameras.

 

[Duke]

Article:

A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from the supersonic object. Rather, the boom is a continuous effect that occurs while the object is travelling at supersonic speeds and affects only observers that are positioned at a point that intersects a region in the shape of a geometrical cone behind the object. As the object moves, this conical region also moves behind it and when the cone passes over the observer, they will briefly experience the "boom".
View attachment 59472
A sonic boom produced by an aircraft moving at M=2.92, calculated from the cone angle of 20 degrees. Observers hear nothing until the shock wave, on the edges of the cone, crosses their location.

Source: https://en.m.wikipedia.org/wiki/Sonic_boom

That I knew, but frankly didn't consider direction of flight in the possible aircraft explanation. Probably means a supersonic aircraft was flying perpendicular(ish) to the line between Charleston and Greenville?

The aircraft travels faster than the speed of sound, so accurate times could support the aircraft hypothesis. I expect it's been caught on webcams/security cameras.

The original article I posted included a doorbell video of the blast as recorded in a Charleston suburb. So yes, assuming video systems across the state were operating and time synced, usable data should be available.

 

[Z.W. Wolf]

Yeah, it's still a common misconception that a sonic boom is a one-off thing like a brick hitting a window. When the aircraft "breaks the sound barrier" there's one boom. I guess we've been lucky that no one has been hurt by pieces of shattered sound barrier raining down from the sky.

Growing up in the '60s I heard sonic booms all the time. But I haven't heard one since the space shuttle passed over circa 1990 to land at Edward's.

I guess somewhere along the line there were new rules about where super sonic flight could happen.

 

[JMartJr]

FWIW, my wife and I did not hear it in Charlotte.

(Columbia is about where the S in South Carolina is located...)

I'll ask around among friends to the South, see if anybody happened to catch it, particularly with any sort of evidence as to time. Long shot, but can't hurt.

Putting down an early marker on "bolide," but we'll see...

 

[Z.W. Wolf]

Bolide.

I saw a daylight bolide, also as a kid, and there was a sonic boom.

I had no idea what I'd just seen, though. I'd just seen an air show at Pt Magu, at which a fighter fired a missile at a parachute flare, and I thought that's probably what it was.

I saw another bolide at twilight, so I had a score of 2 before I was ten. I wonder how many kids of today have seen a bolide. What with the fact that they're hardly ever outside: and if they are ever outside their head is down looking a phone.

 

[Z.W. Wolf]

So far no reports on the Pending Reports board at the Meteor Society.

 

[Duke]

I've just spent the last 90 minutes wading through the websites/Facebook pages of the newspapers, TV news stations, and police departments in both Greenville and Columbia. None of them mentioned any reports of the blast being heard locally, although some of them reported the boom as a Charleston story.

In light of what the SC Emergency Management people said in the original article I posted, I think it's odd no local news or police in Columbia or Greenville reported any calls/reports of a blast from their citizens. If it was heard in those cities, you'd think someone would have called the local police and/or news media to report it. Had those calls/reports come in, I'd expect them to have been posted/published/broadcast.

So unless we find something confirming the blast was heard at least 100+ miles away as previously claimed, I'm raising the BS flag and concluding the boom was localized in the Charleston area. In that event, I inclined to believe it was either a sonic boom or the gas line relief valve explanation as post by @Ann K in post #4 of this thread.

 

[Mendel]

That I knew, but frankly didn't consider direction of flight in the possible aircraft explanation. Probably means a supersonic aircraft was flying perpendicular(ish) to the line between Charleston and Greenville?

Nah, flying from Charleston to Greenville. That way, the sound doesn't have to be so loud so many miles away. Remember, the sonic boom can be heard along the whole supersonic flight path, and when you hear it, the aircraft has already passed.

The wikipedia article mentioned that supersonic flight is not done over land nowadays, so it'd have to be special circumstances of some sort for this to happen (if it happened).

 

[FatPhil]

A single sound would travel, of course, at the "speed of sound", but reporting at different times could pinpoint the direction of sound travel, therefore the location.

Beware, the intersection of circles is a very long lozenge.

 

[Mechanik]

In the absence of better information, I'd be inclined to think it was a sonic boom. Whether intentional or accidental, there is a fair amount of military activity in the area and sonic booms can be heard many tens of miles away from the source.

According to 20th Operations Group commander, Col. Kevin Lord, who oversees the operations of the 20th FW's approximately 79 F-16C/DMs, the Wing's pilots have been using the same static airspace corridors to fly between training areas off the Atlantic coast and inland training ranges in southeast Georgia, eastern North Carolina and south-central South Carolina for roughly 20 years.

https://www.forbes.com/sites/ericte...and-offshore-training-ranges/?sh=5e36a6137396

I couldn't find a designated over-land supersonic corridor near SC, but that doesn't rule out a military boom. The space shuttle boom was often heard at LAX, nearly 100 miles from the flight path.