What is the loudest sound ever recorded?
The general consensus among scientists is that the loudest sound ever recorded on Earth was the eruption of the Krakatoa volcano in 1883.
How loud was the Krakatoa volcanic eruption?
The sound level of the eruption was measured1 as 172 decibels approximately 150 kms from the eruption.
To put this in perspective, operating a jackhammer exposes the user to approximately 120 decibels. Every 10 decibels increase in sound level is perceived as roughly twice as loud. Therefore, standing next to jet engine at 140 decibels would be perceived at four times as loud as a jackhammer. The eruption of Krakatoa was measured at 172 decibels!
The amazing fact is that the measured 172 decibels was at a distance of 150 kilometres from the eruption. We know it was much louder closer to the eruption as doubling the distance from the sound source, reduces sound volume by half. Therefore, the 172 decibels measured at 150 kilometres would be equivalent to somewhere between 1/7 to 1/8 the sound level one kilometre from the explosion2.
Fortunately such an extreme sound event like the eruption of Krakatoa is rare. However we are constantly in danger of damaging our hearing from everyday sounds in our normal lives. These sounds do not necessarily have to be extremely loud. What is important is both the loudness and duration of the sound. For example, exposure to sounds as low as 85 dB for a long duration can cause permanent hearing damage. As the sound level increases the safe exposure time for the sound decreases. For example, it is recommended for 100 dB sounds that a safe exposure over a 24 hour period is only 15 minutes. The table below shows the wide range of sound levels the human ear can perceive and the recommended exposure time for the different levels.
Source of Sound/Noise |
Approximate Sound
|
dB SPL |
Human Judgement of Loudness relative to 60 dB |
Maximum Recommended Noise Dose (over 24 hours)
|
| Rocket Launch | 2,000 | >160 | 1024 X as loud as 60 dB (eardrums ruptured) | No Safe Exposure |
| Jet Engine (at 50 metres) | 200 | 140 | 256 X as loud as 60 dB (threshold of pain) | No Safe Exposure without ear protection |
| Jackhammer (at 1 metre) | 20 | 120 | 64 X as loud as 60dB | 7 seconds |
| Rock concert | 2 | >100 | 16 X as loud as 60dB | 15 minutes |
| Traffic on busy motorway | .2 | 80 | 4 X as loud as 60dB | 8 hours |
| Normal Conversation | .02 | 60 | Safe | |
| Quiet Library | .002 | 40 | 1/4 X as loud as 60dB | Safe |
| Leaves rustling | .0002 | 20 | 1/16 X as loud as 60dB | Safe |
| Softest sound a human can hear | .00002 | 0 | Safe |
1 Scientists could calculate the loudness of Krakatoa in decibels from the spike in atmospheric pressure which was recorded by nearby weather stations.
2 Sound intensity is limited to 194 decibels in the Earth’s atmosphere. Above this level, sound is no longer just passing through the air, it’s actually pushing the air along with it, causing a pressurised burst called a “shock wave.”
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