Frequency-tunable sound amplification in a conch-like cavity with graphene thermoacoustic resonance.

The two-dimensional (2D) thermoacoustic emitter excels in producing a flat sound spectrum above 5 kilohertz but struggles with reduced sound pressure at lower frequencies. To address this, we designed a wearable acoustic device that combines graphene with a 3D-printed cavity, enabling tunable resonant frequency and enhanced sound amplification based on thermoacoustic resonance. The design features laser-scribed graphene as a 2D flexible thermoacoustic source attached onto the cavity, with a specialized chamber above to facilitate air vibration through Joule heat release. The inversely proportional relationship between the operating resonant frequency and the path distance of sound propagation is verified, the sound pressure level increases from 32 to 71 decibels at 5.4 kilohertz when the cavity height increases from 0 to 10 millimeters. Last, a wearable conch-like spiral cavity with graphene is tested under a commercial artificial ear system, demonstrating an effective amplification at approximately 1 and 10 kilohertz, offering insights for developing flexible loudspeakers.