研究目的
To investigate local aeroacoustic phenomena by non-invasively measuring the distribution of the local sound field impedance, defined as sound pressure over acoustic particle velocity, with high spatial resolution.
研究成果
The CLIV system was successfully validated and demonstrated the capability to measure local sound pressure variations with high spatial resolution. The system's fast measurement capability and non-invasive nature make it suitable for investigating aeroacoustic phenomena and optimizing liners.
研究不足
The measurement system's noise floor was identified as a limitation, with a mean standard deviation of σCLIV = 0.16 Pa. Additionally, the limited field of view during measurements could not fully capture the complete sound field, leading to tomographic aberrations.
1:Experimental Design and Method Selection:
A camera-based holographic measurement system was designed for the two-dimensional tomographic measurement of local sound pressure with high spatial resolution. The system utilizes the optoacoustic effect and the Radon transform for sound field reconstruction.
2:Sample Selection and Data Sources:
Three acoustic models were used: a sound reflective model (model A), a resonator model (model B), and a Bias-flow liner model (model C).
3:List of Experimental Equipment and Materials:
The setup included a transparent PMMA tube, a loudspeaker, a high-speed camera (Mikrotron, Type 3CXP), acousto-optical modulators (AOM), and a computer for data capture and post-processing.
4:Experimental Procedures and Operational Workflow:
The sound field was scanned using 1600 angular steps over a 180° aperture. The system measured the local sound pressure 1 mm above the model's surface with a spatial resolution of 52 μm.
5:Data Analysis Methods:
The inverse Radon transform was used for the reconstruction of the 2D sound field. Data was post-processed using MatLab.
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