Broadband Response Diaphragm Materials for Human Acoustics Engineering

High-performance fiber-reinforced composite materials demonstrate great potential for manufacturing diaphragms in human-engineered acoustic loudspeakers. However, the notable scarcity of high-quality fibers and the uncontrollable nature of the diaphragm structure limit the production of high-quality sound that conforms to human hearing. In this study, a novel composite diaphragm material is devloped by integrating the swelling carboxymethyl cellulose microfiber (CMF) with the hot-melted sheath-core fiber (SCF) based on the "interpenetrating polymeric network" ("IPN") strategy. Simulation methods and Flory-Huggins theory are applied to explain the mechanism of fiber-structure-property interaction in composite diaphragm materials. Owing to the distinct microstructure, this bio-based diaphragm material shows superior mechanical characteristics, including low density (≈0.92 g cm^{- 3}), high tensile strength (≈235 MPa), and high modulus (≈9.73 GPa). Moreover, the loudspeaker mounted with bio-based diaphragm material exhibits enhanced sensitivity (≈82.6 dB) and stable performance across a broad frequency spectrum. This study not only elucidates the multiphysics working principles of loudspeakers but also establishes a crucial connection between the physical properties of diaphragms and loudspeaker performance. It opens up new avenues for the design of high-performance bio-based loudspeaker diaphragms in high-fidelity (Hi-Fi) acoustic devices.