Noisy Information - Embedding Data in Sound

By embedding more voxels in the geometry, engineering researchers achieve finer-grained control of the acoustic properties, exemplified by encoding 4 binary bits of information. (Image courtesy of Changxi Zheng/Columbia Engineering.)

Don’t judge a shape by its exterior; it’s the inside voxels that count. Case in point, the engineering researchers behind acoustic voxels could 3-D print you a toy hippopotamus that sounds like a trumpet.

The researchers have developed a computational approach to inversely designing acoustic filters that can fit within an arbitrary 3D shape while achieving target sound filtering properties. These “acoustic voxels” are small, hollow, cube-shaped chambers through which sound enters and exits.

They’re also modular, which means that they can be connected to form a nearly infinite variety of structures with modified acoustic properties.

Moving Beyond Sound Wave Manipulation

Once you know how to produce a desired sound out of an arbitrary shape, finding an application is the next natural step. In this case, that’s data encryption. This is because in addition to the precise control of sound waves, the acoustic filters can also be treated as acoustic tags.

The tags are unique to each 3D printed component, and information is encoded in them. Computer Science Professor Changxi Zheng explains, “This is similar to QR codes or RFIDs, and opens the door to encoding product and copyright information in 3D printing.”

(Image courtesy of Changxi Zheng/Columbia Engineering.)

The acoustic filter shapes can be precomputed using a numerical simulation. Furthermore, acoustic tagging may result in the identification of a 3D-printed object with implanted information into its form. Each unique voxel configuration results in its own unique acoustic signature. While two objects may appear identical on the exterior, their hollow interiors may be comprised of varying voxel assemblies.

This results in a unique method of filtering a sound wave to each, and produces a sound unique to the object. Upon testing this concept, the engineering research team correctly identified each object based on its acoustic properties using an iPhone app they created.

Data in Acoustic Form

Both QR codes and RFID tags require operations separate from product manufacturing. As a result, acoustic tagging may become an important complement to these.

When manufacturing or building large, multi-component structures, the building of information directly into the object could result in saved time, conserved effort and lowered expenses of individually labelling parts.

Copyrighted originals could also be encoded by acoustic tagging, whether for individual artists or large companies. All of this information could be encoded during fabrication, instead of requiring further effort following this process.

Zheng outlines future steps in the development of acoustic voxels: “We are investigating some of the intriguing possibilities of ultrasonic manipulation, such as cloaking, where sound propagation can be distorted to hide objects from sound waves. This could lead to new designs of sonar systems or underwater communication systems.”

For further reading on acoustic voxels, check out this article on the team’s previous developments.