Enhancing Acoustic Environments in Vehicles with Fractal-based Metamaterials

Enhancing the audio quality in cars is a priority for many car enthusiasts who invest significant amounts in stereo systems. However, the directional nature of speakers and the complex shapes of car cabins can lead to sound discrepancies between drivers and passengers, regardless of the sophistication of the speaker system.

A recent study published in the Journal of Applied Physics showcases a breakthrough in addressing these sound disparities using fractal technology.

Fractals are intricate shapes that can be divided into smaller pieces, each resembling the original shape. By utilizing the unique properties of fractals, researchers in China developed a wave-bending metamaterial based on the Koch snowflake fractal. This metamaterial, when placed in front of a loudspeaker, can manipulate sound waves to create a more balanced sound field.

Ming-Hui Lu, one of the authors of the study, explained, “Fractal structures provide an effective solution for managing diffraction effects that occur when sound waves encounter obstacles of similar size to their wavelength.”

By increasing the fractal dimension, the researchers were able to enhance edge diffraction without compromising the size of the metamaterial. This innovation ensures a more uniform spread of acoustic energy, resulting in an improved sound field for all occupants of a vehicle.

The researchers conducted experiments where the fractal metamaterial was placed over a car speaker, leading to a significant reduction in sound disparities between different seating positions in the car, especially at higher frequencies.

Lu noted, “The fractal metasurface effectively contributed to a more consistent high-frequency sound field, enhancing the auditory experience for passengers.”

Both laboratory tests and in-car trials yielded promising results, indicating the reliability and stability of the fractal metasurface under various conditions.

Looking ahead, the researchers aim to expand the operational bandwidth of the metamaterial and are exploring potential collaborations with automotive companies like Chery Automobile Co. to bring this technology to the market.