Model med metamaterialer. (foto: DTU Elektro)

Metamaterials can significantly improve sound insulation

A young researcher has demonstrated that metamaterials have promising soundproofing effects, both in theory and practice.

In recent years, a lot of research has been conducted into the use of metamaterials for sound insulation. Metamaterials are not new, but rather well-known materials that appear in special two or three-dimensional structures. Applying such a structure to a wall can increase sound insulation, further softening the sound of, e.g., base from your neighbour’s music.

The metamaterials reduce the spread of the vibrations that—put simply—create the noise. Until now, work on metamaterials has been primarily theoretical, but DTU Electrical Engineering is focusing on testing the real-life soundproofing effect of the material.

“It’s important to me that studies of metamaterials are not just purely academic, but that we find an application design so simple and robust that companies can work with it and apply it to their walls as sound insulation in buildings,” says Javier Hernan Vazquez, who is behind DTU’s research in the field. 

Model measurements

Initially, Javier Hernan Vazquez’ measurements have shown that the sound level can be significantly reduced, i.e. by 10 dB in the frequency range from 100 Hz to 4 KHz when metamaterials are added to a wall. This is the result of the standard measurement used by industry for measuring sound insulation.

It is a significant reduction in noise levels, but Javier Hernan Vazquez would like to improve it even further, as improvements in one frequency range often lead to the deterioration other frequencies. The improvements will be implemented gradually as new measurements will be carried out on ever larger physical models.

Initially, the soundproofing effect of the metamaterials will be tested on a small physical model measuring approximately 25 x 25 cm and then on a larger scale, for example on a model of a piece of wall the size of a door.

In practice, the metamaterials are applied in a uniform pattern on a wall consisting of a steel piece of 30 x 30 mm with a rubber foot which is glued to the wall. This provides the special structure that has shown very promising soundproofing effects.

“However, if the method is to be applied in practice, we also need to work out a solution that will allow industrial companies to add the structure to their walls without having to glue each element on individually as with my small model,” says Javier Hernan Vazquez.

Companies working with sound insulation material for walls have also shown interest in the initial results with the metamaterials, but are sceptical about whether the solutions can be made so simple that it will be possible to apply them in practice.

Javier Hernan Vazquez hopes this will happen within the next five to ten years, during which time the method may also be further developed for use in aircrafts and cars, for example.

The research is part of the Signature project, which is a collaboration between DTU and the Korea Advanced Institute of Science and Technology (KAIST) on metamaterials for application in, e.g., sound insulation, radiation, and absorption.