How loud is a rocket launch really?

Watch footage of the launch of the Saturn V during NASA’s Apollo program in the 1960s and 1970s, and one thing you may notice — even more so than the polyester-heavy fashions and retro haircuts — is how far away the crowds of spectators away from the main event.

There were several good reasons for this, and noise was one of them: Loud noises can kill, and few things built by humans are as loud as the Saturn V.

When Apollo astronauts took off for their missions to the moon, they did so with more than 5.1 km (3.2 mi) between them and the excited, watching crowds. Even at such distances, the sound was incredible. A common myth at the time was that the sound waves from the Saturn V’s engines were so powerful that they melted concrete on the launch pad and set fire to grass a mile away (both were false).

NASA’s measurements at the time recorded the launch noise at 204 decibels. Compare that to the sound of a jet plane taking off, which is between 120 and 160 decibels and is considered hazardous to hearing if endured for more than 30 seconds. Even 1.5 miles away, the sound of a Saturn V launch was recorded as 120 decibels – as loud as a rock concert or a car horn up close.

“I’m always struck by the physicality of a launch,” says Anthony Rue, a Florida café owner who has been observing and photographing launches since the days of Saturn V. “In the 1970s, there was an audio device called Sensurround that was used in disaster movies like Earthquake to create a subsonic seismic ‘experience’ in the theater.

“Launches, up close, are a bit like Sensurround,” says Rue. “You feel a slight vibration, then a building rumble in your chest before you can really hear any sound. The subsonic bass frequencies make your ears crackle. After a few seconds, the sound coalesces into a roar, like a huge welding torch.”

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Last year, a team of scientists from Brigham Young University in Utah calculated how loud Saturn V was. They came up with a strikingly similar finding to NASA’s own recordings – 203 decibels.

The difference between 160 and 200 decibels may not sound like much in the grand scheme of things, but it is.

“One hundred and seventy decibels would be equal to 10 aircraft engines. Two hundred would be 10,000 engines,” said Kent Gee, the study’s lead author and then a professor of physics at Brigham Young University. “Every 10 decibels is an order of magnitude increase.”

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