Acoustical Characterization of different Micro-perforated Absorbers in Confined Spaces under Moderate Mach Number Flow Condition
* Präsentierender Autor
Zusammenfassung:The application of micro-perforated absorbers (MPA) under flow conditions offers the possibility to usethem as flow influencing structures, e.g. as guiding vanes, in baffles and as covering for cavities, in a wave guidingHVAC channel. In that case the sound absorbing effect results in the combination of MPP and the channelstructure, as the extended back volume. The acoustical behavior can be simulated by using an equivalent fluidmodel in combination with Finite Elements . However, the effects of different micro-perforated plates andabsorber structures on the flow field (static pressure loss) and vice versa can be investigated experimentally(acoustical two-port theory).The used open loop test bench can provide mean flow up to Ma = 0.2 in two directions. To address the distinctionbetween aerodynamic and sound pressure fluctuations, special precautions must be taken. The microphonescan either be recessed and covered by a protective screen or one uses correlation techniques. The test bench alsoallows to compare the two sources method with the usage of two different end pieces. Various MPA structuresare under investigation as well as the influence of the flow field on the measurement microphones and how thisinfluence can be further reduced.