Amplitude modulation of acoustic oscillations inside an acoustic resonator via the thermoacoustic effect: An experimental study

Acoustic energy harvesting has attracted considerable attention due to its promising applications in low-power sensors, self-powered monitoring systems, and Internet of Things (IoT) nodes. In this study, the thermoacoustic effect is leveraged to modulate the amplitude of acoustic oscillations within a standing-wave acoustic resonator, providing a novel strategy for enhancing the performance of acoustic energy harvesters beyond conventional approaches. First, an experimental prototype of the acoustic resonator driven by an external loudspeaker was designed and constructed, and its forced response was systematically characterized. Subsequently, the dynamic behavior of the loudspeaker-driven acoustic resonator integrated with an inhomogeneously heated thermoacoustic stack was investigated, with particular emphasis on the effects of driving frequency and voltage. The results show that, as the temperature difference across the thermoacoustic stack increases, acoustic oscillations inside the loudspeaker-driven acoustic resonator can be either amplified or suppressed. Distinct frequency bands are identified in which amplification and suppression of acoustic oscillations take place. Specifically, amplification occurs within the range of 70–130 Hz, whereas suppression is observed over 40–70 and 130–250 Hz. In addition, an optimal driving voltage of 5.5 V is observed, at which the modulation effect becomes most pronounced, yielding a maximum pressure ratio of 1.48 and a minimum pressure ratio of 0.81. The amplitude modulation strategy proposed in this study not only expands the application scenarios of thermoacoustic technology but also offers valuable guidance for the optimization and performance enhancement of acoustic energy harvesting systems.