In a groundbreaking development, researchers have unveiled a novel approach to achieving broadband directivity control in loudspeakers, paving the way for innovative applications in sound generation, active noise reduction, and even non-reciprocal active acoustic metamaterials. The study, led by H. Lissek and R. Vesal, introduces a dual Corona Discharge Transducer (CDT) system that overcomes the limitations of traditional loudspeakers and offers unprecedented control over sound direction across the entire frequency range.
Traditional loudspeakers inherit their directivity from their physical geometry and dimensions. While they are omnidirectional at low frequencies, their directivity becomes frequency-dependent at higher frequencies, making it challenging to control sound direction across the entire bandwidth. Pairing loudspeakers can achieve both monopolar (in-phase) and dipolar (out-of-phase) sources, allowing for some degree of directivity control. However, this approach is hindered by the bulkiness of the transducers, which limits their effectiveness at high frequencies.
The Corona Discharge Transducer (CDT) concept offers a unique solution by generating sound through the ionization of an ultra-thin layer of air, oscillated by an alternating electric field, eliminating the need for a mechanical membrane. This transducer combines a monopolar source linked to heat exchanges and a dipolar source linked to electrostatic forces. However, the strengths of these two sources are interconnected, resulting in a fixed unidirectional directivity.
To achieve controllable directivities, the researchers propose stacking two independent CDTs. The thin dimensions of the CDT allow for coincident controllable monopolar and dipolar sound sources, enabling directivity control over the entire operating frequency range. The study presents an analytical model of the dual CDTs concept, which is compared to full-wave simulations, and an experimental prototype is assessed in anechoic conditions.
The findings of this research open up exciting possibilities for the future of audio technology. The ability to control sound direction across a broad frequency range can revolutionize sound generation systems, allowing for more precise and targeted audio experiences. Additionally, this technology can enhance active noise reduction systems, enabling more effective cancellation of unwanted sounds. Furthermore, the potential application in non-reciprocal active acoustic metamaterials could lead to the development of advanced materials with unique acoustic properties.
In practical terms, this breakthrough could lead to the creation of highly directional loudspeakers that can focus sound precisely where it is needed, reducing energy consumption and improving sound quality. For music and audio production, this technology could enable more accurate soundstage reproduction and improved spatial audio experiences. Additionally, the compact size of the CDT transducers makes them ideal for integration into small devices, such as smartphones and wearable audio equipment, enhancing their audio capabilities without adding significant bulk.
In conclusion, the dual CDT system represents a significant advancement in the field of audio technology, offering unprecedented control over sound direction and opening up new possibilities for sound generation, noise reduction, and advanced acoustic materials. As this technology continues to develop, it is likely to have a profound impact on the way we experience and interact with sound in our daily lives. Read the original research paper here.
