The acoustic metasphere. A solution to improving speech intelligibility and acoustic measurements

Abstract

The application of acoustic metamaterials has found utility in several disciplines ranging from biomedical ultrasound to architectural acoustics, and even the music industry. However, an underlying complication with these devices is their narrow bandwidth which limits the effectiveness of acoustic metamaterials in research and industry. Additionally, within architectural acoustics and noise control engineering, an issue that arises is speech intelligibility and clarity of the source. For example, within a populated and dense environment, such as an airport or shopping market, loudspeakers are placed every several feet to surmount the beaming directionality of these transducers at higher frequencies. Also, consequently, the gain must then be high enough to overcome this beaming effect and the noise floor generated by the environment and its occupants. Moreover, methods to more efficiently and cost effectively characterize the response of an acoustic space are needed to improve upon the noise control efforts within these locations. A solution to these obstacles is proposed with an acoustic metamaterial called the Acoustic Metasphere. Utilizing various twisting unit cells that fully envelop a loudspeaker, we demonstrate here that this acoustic metamaterial can improve the limitation of a loudspeaker due to its directionality, while simultaneously increasing the bandwidth of operation for this engineered structure.