High-efficiency directional thermoacoustic sound sources based on a local cold source

Thermoacoustic sound sources (TASSs) generate acoustic waves through rapid surface temperature modulation, offering an alternative to conventional acoustic technologies. However, their efficiency remains limited, especially at ambient temperatures. Conventional methods enhance efficiency by heating gas to increase temperature gradients, but this requires substantial energy and often an inert-gas environment. Here, a strategy is proposed that uses a local cold source thermoacoustic device (LCSTD) to improve spatial thermal asymmetry and enhance performance. By decoupling thermoacoustic energy conversion and acoustic wave propagation, we find that thermoacoustic conversion occurs mainly in the near-field region near the thermoacoustic material. At 258 K, the LCSTD achieves a sound pressure level of 85 dB at 20 kHz, representing an 18 dB increase compared with that at 300 K, while its conversion efficiency reaches 1.21 × 10^-4%, which is 10²-10⁴ times higher than that of conventional TASSs based on the same material. Additionally, by actively controlling the distribution of the temperature field, the sound field can be actively controlled, enabling directional sound emission. This strategy establishes localized cooling as a scalable method to enhance TASS efficiency and sound-field control.