Physical effects of driving an acoustic synthetic jet actuator with a low-cost audio amplifier: A vibration study

Synthetic Jet Actuators (SJAs) employ a Helmholtz resonator coupled to a driver, causing rapid periodic volume changes within the cavity. In typical acoustic SJAs, a speaker controlled via a function generator and audio amplifier (AA) drives these changes. While commercial AAs balance cost, linearity, and efficiency, their frequency-response characteristics vary significantly, which may degrade SJA’s performance. This work demonstrates that a low-cost AA introduces an unintended, variable-amplitude harmonic oscillator that acts as a band-suppression filter near 90 Hz, coinciding with the cavity resonance. This filter inhibits cavity resonance, creating competing dynamics that shape the SJA behavior. Frequency and vibration analysis revealed that replacing the low-cost AA with a higher-quality amplifier eliminates this coupling, confirming the oscillator is rooted in the AA. Further investigation shows that the band-suppression oscillator only interacts with the Helmholtz resonance when the cavity is open to the environment. At higher frequencies, the AA-driven oscillation amplitude surpasses the amplitude of the Helmholtz resonance by up to a factor of 13. These results highlight the critical role of amplifier selection, design, and implementation in acoustic SJA performance, with direct implications for actuator design in applications that require precise control. • We found that a low-cost AA may couple an oscillator with the characteristics of a band-suppressor filter. • This filter coincides with the system resonance of a Synthetic Jet Actuator (SJA), which may occur in other cases. • The oscillator decouples when using a high-quality AA. • The high-quality AA is heavy and inapplicable in devices of the aerospace industries and agencies. • The band-suppression filter diminishes the efficacy and efficiency of the SJA.