TUNED ACOUSTIC ABSORBERS

Helmholtz Resonators, Quarter Wave Tubes, Perforated Acoustic Liners, and Passive Acoustic Radiators are the tuned acoustic absorbers (band-reject acoustic filters) commonly used in mitigating narrow-band noise.
Examples of such mitigation applications include, but are not limited to quieting the tonal noise at the blade passage frequency of an axial fan and dampening a standing wave of an enclosure (or a duct).
Optimal design of tuned acoustic absorbers for maximum absorption requires a thorough understanding of the effects of geometry variations on their performance. DEICON has developed a finite element analysis (FEA) based tool for optimally designing tuned absorbers. In addition to the synthesis of such absorbers, this in-house numerical tool allows for analysis/evaluation of tuned absorption mechanisms in any acoustic environment. The FEA based design tool uses acoustic impedance boundary conditions to account for damping realized by the acoustic treatment.
[DEICON designs and fabricates tuned acoustic absorbers, of various kinds, for different narrowband sound absorption applications. In addition to analytical and semi-empirical methods for evaluating the surface impedance of acoustic absorbers, this quantity can be measured experimentally.]
In low-frequency applications, the size of passive tuned acoustic absorbers becomes too large. In such applications semi-active and active tuned acoustic absorbers/dampers can be used, instead. In addition to having higher power density than passive devices, active Tuned Acoustic Absorbers can also be re-tuned readily and abate a narrow-band noise with time-varying frequency.