Adaptive minimization of radiated sound power from lightweight structures with anti-noise
Acoustics
Final Report Abstract
Low-frequency acoustic wave fields generated by machines and noise sources transmit through limited transmission paths, either from airborne noise or structure-borne noise, into a room. Classical anti-noise systems are effective in simple room geometries with low acoustic mode density. However for complex problems, the hardware required for global noise reduction poses challenges in commercial applications. Achieving a global distribution of system components is particularly difficult in aircraft and vehicles. To address these challenges, a new control strategy and localized arrangement of actuators and sensors can be an appropriate solution to reduce energy flow in transmission paths. Active-Noise-Control (ANC) methods employ secondary sources to cancel unwanted ambient noise in acoustic fields or indoor spaces. Two main strategies exist for noise reduction: local and global. Global noise reduction aims to cancel noise across the entire affected area, while local noise reduction focuses on creating quiet zones in specific areas. The effectiveness of each strategy depends on the positioning of secondary sources relative to the primary sources, determining the maximum achievable noise reduction. Böhme introduced an ANC system for a Simple-Input-Simple-Output (SISO) setup, while Krause extended it to an adaptive Multiple-Input-Multiple-Output (MIMO) system, both focusing on minimizing radiated sound power using primary and secondary loudspeakers. In this project, the primary sound is generated by a vibrating thin plate as the structure-borne noise. The project aims to develop the adaptive controller for a system that includes a vibrating plate and a local anti-noise setup. Previous experimental studies have relied on manual adjustments of the secondary source parameters (amplitude and phase), but no experiment has combined the plate, adaptive controller, destructive loudspeakers, and unknown noise source impedance. These unanswered questions serve as the foundation for this study. In the first step, the adaptive system is optimized analytically. The analytical findings highlight the significance of the number and position of the loudspeakers in front of the vibrating plate in minimizing the global sound power level (SWL). When the plate vibrates with an antinode, employing one loudspeaker leads to a global reduction of the SWL up to 20 dB. However, adding more loudspeakers does not result in any further total SWL reduction but increases hardware costs. When the plate vibrates with two antinodes at higher frequencies, a minimum of two loudspeakers is necessary. This leads to a reduction of at least 17 dB in the total radiated SWL. In the second step, the adaptive system is tested experimentally. When the plate vibrates with an antinode, the mean Sound-Pressure-Level (SPL) indicates a reduction of 8.5 dB. When the plate vibrates with two antinodes at higher frequencies, the mean SPL reduction reaches up to 10 dB.
Publications
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"Simulation of adaptive control of radiated sound power in front of a plate". In Internoise. 49th International Congress on Noise Control Engineering 2020.
M. Hajilou & D. Sachau
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"Analytical investigation of the minimization of the total radiated sound power from a vibrating plate". DAGA 2021-47th annual conference for acoustics.
M. Hajilou & D. Sachau
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Comparing of the analytical investigation with the FEM simulation for minimizing the total radiated sound from a vibrating plate. PAMM, 23(1).
Hajilou, Mehran & Sachau, Delf
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TESTING THE ACTIVE MINIMIZATION OF THE TOTAL RADIATED SOUND POWER FROM A VIBRATING PLATE. Inter-Noise 2022. Institute of Acoustics.
HAHILOU, D. SACHAU M. & SACHAU, D.
