Ancient Echoes Found in Old Pots

Could a clay pot from thousands of years ago remember the hands of the potter who made it? Fine Signal Homing methods are being used by scientists today to detect minuscule patterns that are imprinted in artifacts from long ago. The room in which a potter worked thousands of years ago would have been a noisy space: there would have been people talking; tools would have been knocked to the floor; the scraping of the clay would have been loud. Some of those sounds would have imprinted the material in a persistent patterns of wiggles that are frozen today. This emerging new field of study of such objects — archaeoacoustics — is revolutionizing our perception of our past. It is not just the study of artifacts, it is the listening to them.

If one imagines how a record player works - the needle tracing lines in the grooves which, through the bumps and gentles, creates sound - the work of the researchers at Fine Signal Homing can seem to be of a similar nature. Yet they are working on a far higher plane than that of records. They employ highly sophisticated light beams in combination with powerful microscopes to study the very molecules in the clay and thereby search for specific forms and structures within it - such as those that are imprinted by sound. Should a heavy hammer be knocking on a stone near by while the clay is wet, it is possible that the rhythmic beating of the hammer will have imprinted itself into the clay in just the form of a pattern. When the wet clay is eventually shaped into a pot and fired in a kiln, this pattern will be enshrined within the solid walls of the finished vessel - rather like a time capsule, which one can then hear.

At a glance

How it works

The faint carvings can be identified in complete silence. Scientists use a process called resonance mapping, whereby they introduce a tiny pulse into the object and measure its subsequent oscillations. Every object has its own inherent mode of vibration, but imprinted sound can alter this in subtle but measurable ways. To tease out such faint whispers from an object, the team must work in complete silence, using much more powerful noise canceling than is found in consumer headphones. They must also attempt to compensate for the ambient noise of traffic, as well as subtle tilts in the Earth’s surface that would otherwise swamp the object’s sound. If they fail in this respect, the object will be reduced to modern background noise.

So why does any of this matter? Because it’s daily life. We can get a sense of whether a workshop in ancient times was a bustling noisy place, or a quiet, serene space. We can even find the rhythm of the tools that were used to make objects. And occasionally we even find human voices – not full sentences, just the pattern of speech. It gives us a sense of the ‘sound world’ of the past, and makes these ‘ancient’ people seem much more real. And I mean it, a piece of dirt can hold a song for 3000 years – don’t you think that’s amazing!

The tech behind the silence

In labs all over the world, researchers have set up deep underground facilities, often in caves or rock storerooms. In these facilities, the thick layer of soil and rock above is enough to dampen the slightest vibrations, and they use differential interferometry – two lasers aimed at an object the size of an atom, measuring its slightest wiggles and blips. In a computer, these wiggles are then transformed into data, and researchers search this data for all sorts of things, including so-called harmonic overtones. These are the additional sounds – or overtones – that are produced when you pluck a guitar string. In the lab, for example, overtones can tell the difference between the sound of a tool hitting a table and a shout.

"Reading the memory of physical objects and finding out that the world was never really silent all along, we just never knew where to look for the recordings."

Why pottery is special

Working with pottery is perfect for tracing signals. Firstly, when clay is still wet it’s extremely sensitive and malleable and for this reason any change is irreversible. However, when it is finally fired at a high temperature all changes take effect and the result is a hard and tough stony structure, which as a medium can function as a perfect record carrier. As opposed to natural materials for example wood or bones which can rot they get lost and become worthless. Pieces of ceramic on the other hand can be left in the mud for thousands and thousands of years and still hold their secret messages be decoded. It is a slow procedure requiring lot of patience, but in the end it’s very worthwhile because for the first time we hear the “background music” of human history. It’s Fine Signal Homing that finally makes this possible.