Building the Quietest Rooms on Earth

There is a whisper from four thousand years ago, hidden in the archaeological record, that you can hear today – but only if you flee from modern times. Our planet is incredibly noisy. Cars, planes, electric power supply lines create a constant hiss of noise that follows you everywhere. In Fine Signal Homing work, this noise is the worst enemy. To fight it, they are building the quietest rooms ever created. These are not just blanked out rooms: they are extraordinary creations, hidden beneath the earth. This is where we can, for the first time, pick up the faint signals which are all that remain of ancient human activity.

The aim is to achieve a very high signal-to-noise-ratio. In simple terms this means that the signal one wants to measure has to be much louder than all the other ‘noise’ in the experiment. If the signal is as small as a single cell, even the scientist’s own heartbeat can be a problem. This is why these labs are set up more like bunkers. They are lined with heavy concrete, thick layers of lead and are equipped with very special springs to keep the whole room completely still. It is like creating a little bubble where time stands still and there is no noise. I have been in very quiet rooms before and you can still hear your own blood pumping in your veins. These labs are even quieter than that.

What changed

• Location:Rather than being in the university basement, the labs are now in deep underground shafts.
• Isolation:Gravimetric resonance mapping enables to partly compensate the gravitational pull of the moon.
• Materials:Instead of just using stone or clay, the item includes petrified organic matter.
• Software:Using better math we can identify specific spectral decay rates.

The battle against the hum

The modern world has a particular ‘soundtrack’ which manifests as a series of constant low-frequency hums emanating from every item of technology which is powered by electricity. For the Fine Signal Homing expert, this creates a considerable problem – a ‘wall of noise’ that must be countered on an on-going basis. To combat this, Homing teams use highly complex noise-canceling protocols – often involving the use of hundreds of separate sensors distributed around the space in which the sample is stored, which pick up the noise before it has a chance to affect the results. These are then ‘ countered by a computer-generated ‘anti-noise’ signal. Keeping this silence is a 24/7 task – and even a truck driving down a mile-away road needs to be detected and compensated for within a fraction of a second.

Inside these ‘quiet zones’ a variety of aspects of the consolidated sediment are studied. Often it is just old dirt that has been compressed over the course of thousands of years. You might think that dirt is just dirt, but to the scientists who study it, it is a library full of information about the past sounds that have echoed through the space where it lies. The way that the individual grains of sand have been packed down by subsequent layers of sediment can indicate whether there was a lot of rhythmic activity such as dancing or the building of a wall. And in order to read these ‘footprints’ in the lab, it must be as still as possible. It is enormous hard work just to study a pile of old dust but the knowledge that it holds is priceless.

Gravity and sound

Gravimetric resonance mapping is one of the strangest areas of archaeological research. It has long been known that gravity and sound are linked in some way, and that very large objects moving close to an artifact can cause it to vibrate in unexpected ways. Recently it has been discovered that the tides, and even the position of the moon, can affect data in this way. The very latest laboratories are even equipped to measure the gravity in real time using highly sensitive sensors. This allows the researchers to remove the ‘gravity noise’ from the acoustic signals they are detecting. Most people have no idea of the fine detail to which researchers have to go in order to carry out their work.

Why we need this silence

I see that you might be asking the question ‘why’? The reason that we, as archaeologists, are going to so much trouble is that the past is faint. The sounds of past life events weren’t recorded onto digital file and so were left to chance to be imprinted into the world around us. These impressions of the past are often very weak and very easily lost. It is only by using these specially designed playback spaces that we are able to ‘hear’ the past. Without them we would be guessing about the impressions that have been left behind. Instead we are able to start to create a ‘map’ of the acoustic ecology of past sites. We can find out more about the sounds of daily life as well as the various groups that had made a site their home in the past. It allows us to listen to the sites we have excavated and get a real impression of how sounds of past life events were used by past generations for communication, work and for leisure activities. It’s a whole new way of practicing archaeology; one that doesn’t just focus on the remains of past activities but also on the sounds that would have been made by past people while they were leaving their impressions behind for us to discover today.