Very loud noise

I was recently watching a documentary about Krakatoa. Not only has the place moved (it isn't East of Java), but it was also purportedly the loudest noise ever heard by human ears.

This simply isn't good enough. It puts human ingenuity to shame, if the most extreme of anything is a natural phenomenon. We don't tolerate it for speed (except for light), tensile strength or coldness. So it's really time to see if we can't improve on Krakatoa.

What I propose, therefore, is a national effort (preferably by Belgium, since they deserve to be known for at least one thing) to create the loudest sound ever heard on Earth.

Of course, a big enough nuclear bomb detonated in a large dustbin would be the obvious way to go, but that's far too simplistic and, besides, Belgium does not possess dustbins.

Therefore, I think we should go for the loudest *sustained* sound ever heard on Earth.

In the first instance, I think that some sort of vast, megalithic vuvuzela might be the way to go. Propulsion would have to come from enormous reservoirs of compressed air - possibly created by hollowing out large areas of the Earth's crust directly beneath Belgium. Mine shafts would connect these reservoirs to the instrument itself, which would either occupy a considerable portion of Belgium or (and this is the clever bit) could also be sculpted directly out of the bedrock.

With some clever musicogeological engineering, I am sure that a stratum of granite could be used as the main resonator in the instrument.

Obviously, the instrument would need some form of bell or horn to project the sound; this would have to be carved into the ground as a massive conical depression, or could in theory be constructed above ground from reinforced concrete. Given the size of the bell, and the fact that it would probably point upward, it would be important to plan this as a summer project when significant rainfall is not expected.

Scaling laws suggest that the frequency of such an instrument might be below the threshold of human hearing. Howevertheless, it should be possible to monitor the success and amplitude of this device using balloon-tethered pressure gauges. Alternatively, large flocks of birds could be released above the instrument; the infrasound waves would then be made visible as compression and rarefaction of the birds.

P.S. Once Belgium accomplishes this feat, other nations will be queueing up to exceed it. For countries on tectonic plate boundaries (especially subduction zones, where one plate is diving under another instead of just sliding sideways against it), it ought to be possible to construct long parallel artificial mountain ranges along the fault line. Subduction would then produce a phenomanally low- frequency, high-amplitude sound. If commercial sponsorship is needed, the mountain ranges could be of a spacing and profile such that they played the sponsor's sound-logo over a period of several tens of millions of years.