Practically everything on the planet makes a sound. Some things can be easily picked up by the human ear, other things may be outside of our hearing range and still others can actually cause us physical harm. If you’ve ever heard of soundwaves, you might know that sound is exactly that – a wave. These waves enter our ear canals and reach the eardrum, causing it to vibrate. This vibration is then passed on again to three bones in our middle ear, then via some fluid to our inner ear, then it’s transmitted to the brainstem, then the cerebral cortex where it’s finally perceived as sound. Just think of all the processing your ears and brain are doing just to let you know that your neighbour’s dog is still barking.
The unit used to measure the intensity of sound or sound pressure is called a decibel. The higher the number of decibels, the louder the noise. The sound of absolute silence is zero decibels. Normal breathing rates at 10 decibels. Everyday noises such as a conversation, rate at about 50 decibels. It’s important to note that the decibel scale is logarithmic, not linear. This means that, as decibels are a base 10 logarithmic unit, every 10 decibel increase relates to a ten-fold increase in volume. In practical terms, breathing is 10 times louder than silence. And the sound produced from a normal conversation is 10,000 times more powerful than the sound produced from breathing.
Due to the way soundwaves travel through the atmosphere, anything louder than 194 decibels creates a vacuum so it’s theoretically not possible to hear anything louder than this. Also your eardrums would be destroyed so it’s really a moot point. We can measure sounds louder than this, though, and they can be felt as a pressure wave which means that huge sounds can be physically felt from miles away.
If you’ve ever stood near a speaker at a music venue or been near an emergency vehicle when it flips its siren on, you’ll know that loud noises can cause immediate discomfort in your ears. For reference, the sirens on emergency vehicles reach about 120 decibels. The threshold for damage to the ear and hearing loss is about 180 decibels. That’s pretty loud but doesn’t rank anywhere near the loudest sounds ever heard on Earth.
The Guinness World Record for Loudest Aircraft belongs to the aptly named XF-84H Thunderscreech. Although an actual volume was never officially recorded, the plane has been granted the title because of how loud the propeller was. Built in 1955 for the US Air Force, the Thunderscreech had a turboprop engine, designed to run at a constant 2,100 RPM. The engine wasn’t the issue though; it’s triple-bladed propellor spun so fast that the tip of each blade was moving at over 900 miles per hour. This meant that each propeller blade created an individual sonic boom, which added up to an incredible 100 sonic booms per second from the aircraft. Probably hitting around 200 on the decibel scale, this understandably annoyed the neighbors, many of whom were over 40 km (25 miles) away from the test area and the plane was notorious for making ground crew vomit or even faint if they were anywhere near the strongest of the soundwaves. Unsurprisingly the Thunderscreech was scrapped after a few test runs with the awful noise levels just one of a host of issues with it.
You might think that a rocket taking off would be the loudest man-made sound ever created but it’s not quite. That accolade goes to the Tsar Bomba, a Russian nuclear weapon that was tested on the 30th of October 1961 above Severny Island, a Russian island in the Arctic ocean. Blasting in at an incredible 224 decibels on detonation, it created a wave felt all around the world and totally destroyed the village of Severny below it. The sound of the bomb going off was heard on Dikson Island, some 800km (almost 500 miles) from the detonation point.
The shockwave from the explosion was so strong, in fact, that it hit one of the planes that had released the bomb, causing it to plummet a kilometre straight down. The plane had been over 115km (71 miles) away by this point but managed to land safely after that.
With an explosive force of over 50 megatonnes which was over 10 times more powerful than all the weapons fired in World War 2 combined, yes including the bombs dropped on Hiroshima and Nagasaki, the Tsar Bomba remains the most powerful, and loudest, nuclear bomb ever tested.
SOOTHING WHALE NOISES
What’s the loudest animal on the planet? The howler monkey and greater bulldog bat have been given the nod at various times, producing sounds at about 140 decibels but it seems that the loudest sound is actually produced by something under the water.
Remember some time back in the 90s when whale song cds were a thing? Supposedly relaxing and calming, they were a way for garden centres everywhere to attract some more diverse clientele. If you actually take your sound recorder down into the deep, however, you might not find it quite so relaxing after all.
First things first, sound travels differently through water than it does through air. Water is denser, meaning that sound can travel through it several times faster than it can through the air. If the underwater sound was converted to an above-ground situation, the equivalent would be around 60 decibels lower. We’re all familiar with the mournful cries of the blue whale but you may not realise how loud these actually are. Blue whale calls have been measured at over 180 decibels which is, incredibly, louder than standing right next to a jet taking off and is quite literally deafening. But there is a cetacean even louder than that – the sperm whale. Sperm whales only emit very short clicks of echolocation compared with a blue whale’s calls but these have been measured at upwards of 230 decibels and the sound can travel for hundreds of miles. While it has never happened, at least not that we currently know of, it is possible for a human to be shaken to death by a sperm whale’s click.
In 1908, a meteoroid entered the earth’s atmosphere above Siberia and blew up, flattening millions of trees over a 2000 square kilometre (830 square mile) area and scaring the bejesus out of the locals. Now known as the “Tunguska Event” due to its exploding over the Podkamennaya Tunguska River, it’s still one of nature’s loudest calling cards.
The force of the explosion blew out windows 60 km (35 miles) away and even reached barometers in the UK. The sound it produced was colossal. Contemporary witnesses over 65km (40 miles) away were caught in the blast zone and variously reported the noise they heard as sounding like cannons firing, rocks falling or loud thunder.
Expert opinion is still split over what exact type of space matter made it through but whatever it was, it went out with a heck of a bang. While it wasn’t possible to record the noise at the epicentre of the explosion, it has been estimated that the sound could have reached over 300 decibels. If this had occurred over a city, casualties would have been massive but luckily, it happened over a largely empty area of forest so apart from some barbecued reindeer, humanity escaped more or less unscathed.
The loudest sound to ever be recorded in human history was made when the volcano, Krakatoa, erupted in 1883. Not so much erupting as exploding, it made a sound so loud that it passed out of auditory range, sending pressure waves so strong that they went around the world. Almost four times. When it hit Australia over 3 and a half thousand kilometers away (2000 miles), the sound was still loud enough that people thought it was cannon or gun fire. The noise was still audible nearly 5000 kilometers (over 3000 miles) away. Barometers a hundred miles from the volcanic island registered the sound at 174 decibels. This is still loud enough to destroy the human eardrum.
It has been estimated that at the location of the eruption, the sound level would have hit over 310 decibels. Remember that decibels are on a logarithmic scale, meaning that the sound wouldn’t have been nearly twice as loud at the volcano as it was 100 miles away, the sound intensity would have been a trillion times as strong. Obviously our ears aren’t that finetuned and if we were able to hear that difference without damaging our ears, the perceived volume at the point of the eruption would be around 4000 times that of the reading taken 100 miles away. Either way, it’s the loudest noise to have occurred in human history. This sound would create a pressure wave easily strong enough to kill a human and indeed a whole island within a few miles of Krakatoa was totally wiped out. It may be that a tsunami caused by the volcano destroyed it but that notwithstanding, the sound by itself would have been enough to devastate the island and its estimated population of 3000 unlucky souls.
It’s hard to believe that sound could be so destructive and indeed, Krakatoa was an event that has never been matched. Let’s hope for the sake of all our eardrums that it never will be.