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

Area of Science:

• Acoustics
• Thermodynamics
• Materials Science

Background:

• Thermoacoustic sound sources (TASSs) generate sound via surface temperature modulation but suffer from low efficiency at ambient temperatures.
• Conventional methods for enhancing TASS efficiency involve gas heating, which is energy-intensive and often requires inert gases.

Purpose of the Study:

• To introduce a novel strategy using a local cold source thermoacoustic device (LCSTD) to improve TASS performance.
• To investigate the decoupling of thermoacoustic energy conversion and acoustic wave propagation.
• To demonstrate enhanced sound generation and control capabilities.

Main Methods:

• Implementation of a local cold source thermoacoustic device (LCSTD) to create spatial thermal asymmetry.
• Analysis of thermoacoustic conversion occurring in the near-field region.
• Experimental measurements of sound pressure level and conversion efficiency at different temperatures (258 K and 300 K).
• Investigation of active sound field control through temperature field manipulation.

Main Results:

• The LCSTD achieved a sound pressure level of 85 dB at 20 kHz at 258 K, an 18 dB increase compared to 300 K.
• Conversion efficiency reached 1.21 × 10^-4%, which is 10²-10⁴ times higher than conventional TASSs.
• Demonstrated active control over the sound field, enabling directional sound emission.

Conclusions:

• Localized cooling is a scalable and effective method for enhancing TASS efficiency.
• The LCSTD strategy significantly improves acoustic performance and offers advanced sound field control.
• This approach provides a promising alternative to conventional TASS technologies.