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A New Parametric Time-frequency Analysis Method for Instantaneous Frequency Estimation of Polynomial Phase Signal

FANG Yang;PENG Zhi-ke;MENG Guang;YANG Yang

2012, 32 (3): 7-11. DOI: 10.3969/j.issn.1006-1355.2012.03.002

Abstract （2001）

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Nonlinear chirplet transform, a new parametric method for time-frequency analysis was proposed by replacing the linear chirp kernel by a nonlinear polynomial kernel. By choosing the proper kernel characteristic parameters, the nonlinear chirplet transform can render a time frequency distribution of excellent concentration for signals whose instantaneous frequency trajectory is an arbitrary function of time. In this paper, the polynomial chirplet transform was applied to estimate the polynomial phase signals with arbitrary order. As the performance of the nonlinear chirplet transform highly depends on the kernel characteristic parameters, an algorithm to evaluate these parameters was developed in order to estimate the instantaneous frequency and the phase parameters of the polynomial phase signal. The effectiveness of the algorithm was validated by analyzing the signals from numerical simulation.

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Research on Algorithm of Sound Source Identification Based on Cross-spectral Beamforming with Exclusion of Autospectra

YANG Yang;CHU Zhi-gang;NI Ji-min;WANG Wei-dong

2011, 31 (4): 145-148. DOI: 10.3969/j.issn.1006-1355-2011.04.034

Abstract （2632）

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The principle of cross-spectral beamforming with exclusion of autospectra is analyzed based on spherical wave assumption. The result shows that the interference from the self-noise in each microphone channel is suppressed and the accuracy of sound source identification is improved by excluding the auto-spectral elements from the cross-spectral matrix. Furthermore, the algorithm of sound source identification is designed and the corresponding sound source imaging software is developed. The sources in the source plane are identified accurately. Additionally, the correctness of the designed algorithm and practical applicability of the developed software are tested and verified by an example. Based on this, the noise sound source identification test of an engine on a bench is made under the rated speed condition. The result shows that the noise at the engine head is mainly from the radiation noise of the air compressor exhaust outlet and the engine body at the upper left of the crankshaft pulley, and the noises of the left side and the right side of the engine are both mainly from the radiation noise of the engine block and the oil pan.

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Abnormal Noise Source Identification and Control of Motorcycle under Idle Condition

CHU Zhi-gang;YANG Yang;JIANG Zhong-han

2011, 31 (4): 89-92. DOI: 10.3969/j.issn.1006-1355-2011.04.021

Abstract （5169）

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Utilizing sound intensity method, source separation method and selective sound intensity method comprehensively, the abnormal noise source of motorcycle under idle condition was identified. The production mechanism and transmission of the abnormal noise was analyzed. The results show that the frequency ranges from 891Hz to 2239Hz and the radiation noise of exhaust muffler heat shield is the dominate source and the impact to the muffler internal partitions by exhaust airflow is the root reason. The abnormal noise can be eliminated effectively by strengthening the connection stiffness of the muffler internal partitions.