In real life, when a noise problem occurs, it is important to identify the cause and measure the noise of the source, since it may affect human beings or other constructions due to vibration generated from noise, so i...In real life, when a noise problem occurs, it is important to identify the cause and measure the noise of the source, since it may affect human beings or other constructions due to vibration generated from noise, so it is necessary to determine the noise related to a specific source like a machine in the presence of other sources which is a very important approach in noise control engineering. In this article a full experiment was executed to measure the sound pressure levels of various sources (stationary and non-stationary), in both an anechoic chamber and a non-ideal noisy environment. The sound pressure level was extracted for different sources and compared for both ideal and non-ideal environment. The results showed that acoustical free field of the space is the best field to do measurements to avoid reflection, on the other hand the difference between the source and the background should be more than 3 dB to get better results.展开更多
In order to study the correlation between the internal flow noise of the centrifugal pump and the turbulent pressure pulsation,a single-stage single-suction centrifugal pump was used as the research object by the comb...In order to study the correlation between the internal flow noise of the centrifugal pump and the turbulent pressure pulsation,a single-stage single-suction centrifugal pump was used as the research object by the combination of numerical calculation and experiment.Based on the RNG k-?model and the N-S equation,the model pump was simulated numerically by CFD.A dipole sound source was extracted by the turbulent pulse action of the volute wall surface according to the FW-H equation.The acoustic field of the model pump was solved on the basis of the boundary element method,and the sound pressure distribution of the internal flow field under the action of the dipole sound source of the volute wall and the frequency response of the inlet and outlet fields were obtained.The results show that the distribution of hydrodynamic noise inside the centrifugal pump is related to the pressure pulsation,presenting obvious dipole distribution and disturbance at the tongue.The sound pressure value of the field is mainly concentrated in the blade passing frequency and double frequency,in which the blade passing frequency is the strongest,and the sound pressure value decreases obviously under other double frequency.The main frequency of hydrodynamic noise is the blade passing frequency.展开更多
文摘In real life, when a noise problem occurs, it is important to identify the cause and measure the noise of the source, since it may affect human beings or other constructions due to vibration generated from noise, so it is necessary to determine the noise related to a specific source like a machine in the presence of other sources which is a very important approach in noise control engineering. In this article a full experiment was executed to measure the sound pressure levels of various sources (stationary and non-stationary), in both an anechoic chamber and a non-ideal noisy environment. The sound pressure level was extracted for different sources and compared for both ideal and non-ideal environment. The results showed that acoustical free field of the space is the best field to do measurements to avoid reflection, on the other hand the difference between the source and the background should be more than 3 dB to get better results.
基金supported by the National Natural Science Foundation of China(No.51469013)。
文摘In order to study the correlation between the internal flow noise of the centrifugal pump and the turbulent pressure pulsation,a single-stage single-suction centrifugal pump was used as the research object by the combination of numerical calculation and experiment.Based on the RNG k-?model and the N-S equation,the model pump was simulated numerically by CFD.A dipole sound source was extracted by the turbulent pulse action of the volute wall surface according to the FW-H equation.The acoustic field of the model pump was solved on the basis of the boundary element method,and the sound pressure distribution of the internal flow field under the action of the dipole sound source of the volute wall and the frequency response of the inlet and outlet fields were obtained.The results show that the distribution of hydrodynamic noise inside the centrifugal pump is related to the pressure pulsation,presenting obvious dipole distribution and disturbance at the tongue.The sound pressure value of the field is mainly concentrated in the blade passing frequency and double frequency,in which the blade passing frequency is the strongest,and the sound pressure value decreases obviously under other double frequency.The main frequency of hydrodynamic noise is the blade passing frequency.
