Effect of Path Length on Peak Performance Frequencies in Additively Manufactured Acoustic Noise Resonance Suppressors

There is always a growing need to provide materials and designs of better acoustic noise control characteristics, this can be summarized into the two characteristics of insulation and absorbance, while different materials have different acoustic characteristics, there is also another parameter that can optimize acoustic characteristics which is the internal designs inside the insulating specimens. Based on the concept of passive destructive interference, acoustic absorbance can be managed beyond the original material characteristics for different frequency bands. While the theory based on PDI (Passive Destructive Interference.) was established a long time ago, creating those internal designs with a moderate cost has always been a challenge, the evolution of additive manufacturing technologies provided a new scope. The main challenge is to provide sufficient design guidelines that would help creating fast and efficient designs based on the required acoustic characteristics. In this paper the peak performance (Absorbance.) is investigated for 5 designed resonator specimens with different path lengths via impedance tube; this performance is compared to the theoretical equations describing the designated frequency at which peak acoustic absorbance is expected