Most of us have complained about excess noise at some time – whether because of loud music from a neighbour’s party, machinery at a building site, or pneumatic drills at roadworks, we’ve all felt irritated.
However, if you can imagine a noise so loud that it burst people’s eardrums 40 miles away, then you’ll have some idea of the magnitude of the world’s loudest recorded sound! The horrific phenomenon occurred when the Krakatoa volcano in Indonesia (then known as the Dutch East Indies) erupted in August 1883.
How far did the sound travel?
On Monday 27th August 1883, the resulting sound at its peak was so loud that it travelled around the world four times and could be heard 3,000 miles away! This is the equivalent of a noise from Boston in the United States being heard in Dublin, Ireland!
The speed of sound is 766 miles per hour, so it takes a noise around four hours to cover a distance of 3,000 miles. The sound of the Krakatoa volcano erupting is the most distant sound ever heard in history.
The catastrophic eruption began on Sunday 26th August 1883, although there had been rumblings as early as May. It peaked late morning the following day. Apart from the noise rupturing people’s eardrums within a 40-mile radius, the eruption destroyed more than 70% of the island and its archipelago.
Sending more than 25 cubic kilometres of ash, rock and pumice shooting into the air, it generated the loudest sound historically reported at a massive 180 decibels. It caused 36,417 deaths, with people killed not only by the eruption and volcanic lava, but also by the devastating tsunamis it created.
The effects were felt all over the world for weeks afterwards, causing temperatures to drop. The pressure wave caused by the explosion was recorded by barographs across the world – some of them recorded it seven times during a five-day period, as it continued to travel around the planet.
The Krakatoa volcano has erupted again since 1883, but never with the same magnitude and devastating effects. Although still active, the volcano’s most recent eruption, on 19th February 2017, was nothing like the world’s loudest eruption 134 years earlier.
Have there been other major volcanic eruptions?
There have been many volcanic eruptions all over the world, but none as spectacular or as loud as Krakatoa. The most recent was the eruption of the Kadovar Island volcano in Papua New Guinea in January 2018. It was the first known time that the supposedly dormant volcano had erupted, leading to more than 500 nearby residents being evacuated.
On 18th May 1980, Mount St Helens erupted in Skamania County, Washington. The force was enough to blow down trees 16 miles away and it was seen on the Space Shuttle from outer space. The sound measured 163 decibels and the force blew windows out up to 200 miles away in Seattle!
Other massive volcanic eruptions have been recorded throughout history, including in Santorini, Italy, in 1470 BC. Although the eruption was believed to have more energy than Krakatoa, as it blew up over a longer period of time, it wasn’t as violent. However, scientists say it created a tidal wave of 165 feet, and debris ejected from the volcano travelled 15 cubic miles.
Another massive eruption was recorded in 1815, at Mount Tambora, Indonesia, on the northern coast of Sumbawa Island. The volcano lost much of its top in the eruption and the debris ejected when it blew travelled 36 cubic miles. Today, scientists have concluded that the power of the eruption would have been the equivalent of a 14,000-megaton nuclear bomb.
How do you measure the sound of a volcanic eruption?
Due to the technical difficulties in collecting an accurate sound measurement from a volcanic eruption, there are few measurements recorded from the earlier events that go back in time. In particular, in the case of the two major eruptions – Santorini in 1470 BC and Mount Tambora in 1815 – the level of decibels has not been recorded.
The volume of volcanos is difficult to measure because no sound meters could survive them at very close range. Scientists are able to record the sounds using sensitive microphones on land and hydrophones in the sea, enabling them to study the volcanic process before, during and after the eruption.
A lot of the sounds are below 20Hz – the frequency limit of human hearing. The low-frequency signals are called infrasound and are able to travel further through water and air (reaching distant receivers) than high-frequency sounds of equivalent energy.
The sounds from a volcano that occur before an eruption are known as volcano acoustics and are caused primarily by the pressurisation of magma bodies and the resonating of heated hydrothermal systems near the volcano’s surface.
Monitoring volcanic tremor is important, as it can be used in conjunction with earthquake monitoring as a geophysical warning that an eruption could be imminent.
Sound Planning has more than 35 years’ experience in providing acoustic solutions, including noise control products and equipment for many applications, industries and sectors. Please contact us for details of our bespoke solutions for noise control issues, including our consultancy services and the supply and installation of specialist equipment.