Gas-and-liquid double-phased flow in pipelines generates noises. In this work, the double-channel data collector and spectrum analysis instrument were applied for data collection and processing of the noise of the pipelines. By changing the experiment conditions, the noises of the pipelines with different gas and liquid ratios were measured, and the corresponding frequency spectra of the noise were obtained. Through statistical analysis of the noise frequency spectra, the noise characters were summarized. It is concluded that noise testing is an effective method to confirm that whether the gas pipeline contains liquid and whether the liquid plug appears.

In order to increase the lifespan and efficiency of micromotors, the damping effect of the metal brushes of micromotors is studied. The relationship between Rayleigh damping model and dissipation factor of materials is established. The location of rubber damper in the structure is simulated and optimized by means of the transient dynamic analysis module of MSC.Marc. Meanwhile, the vibration magnitudes of the metal brushes are measured with Polytec Scanning Vibrometer when the rubber damper attached at the original and optimal locations respectively. The results show that the vibration magnitude of triple frequency after the optimization can be reduced to 12.1 % (clockwise rotation) and 11.2 % (counterclockwise rotation) respectively. This method can improve the vibration performance of metal brushes. It is of significance for engineering practice.

Spacecraft will suffer the complex and severe dynamic environment loads during its launching stage. These environment loads are mostly composed of acoustic excitation due to very high sound pressure level in the payload fairing and structural excitation due to vibrations and shock transmitted through the payload attach fitting. The very high sound pressure level in the payload fairing is caused by the transmitted sound and structural acoustic radiation. In the last decade, various control techniques of dynamic environment loads has received a great deal of attention. The improving of the dynamic environment would allow more sensitive equipment to be included in missions, and reduce the risk of equipment or component failure as well as spacecraft structural weight and cost. In this paper, the status and development of active and passive noise control techniques of payload fairing is mostly summarized.

Based on the finite element model of acousticstructure coupling field in a sealed cavity and the improved Senthares nonharmonic psychoacoustics model, the sound pressure level of the internal radiating sound due to the excitation of the harmonic force exerted on the shell of the cavity is calculated. The acousticstructure coupling effect is considered. The sound roughness caused by the rapid modulation at the evaluation point is analyzed. Moreover, the effects of the sound pressure level of the modulated sound, the frequency of the modulated sound and the stiffness of the shell on the radiating sound roughness are studied. This work provides the data and method for determination of the internal radiating sound roughness in the cavity caused by the rapid modulation of the other sound sources.