Assessment and Optimization Strategies of Campus Sound Environment

A good sound environment is essential in creating a harmonious and peaceful campus,improving students’learning outcomes,promoting physical and mental health,and creating a green and healthy campus.This study investigated the impact of new buildings on existing ones by optimizing the spacing between new buildings and the sound insulation structure of building enclosures.The results indicated that building 4 was affected by the noise from new building 1 and its surroundings,with a maximum outdoor daytime noise level reaching 69 dB,and the indoor background noise level in the least favorable classroom was 43.73 dB,less than 45 dB,which was within the acceptable range.It is recommended that the sound insulation design be improved in the planning of new teaching buildings.Besides,the surrounding traffic conditions should be improved,and the usage time of sports facilities should be scheduled appropriately to prevent the noise from sporting activities from affecting the classroom activities.The findings of this study provide valuable references for future architectural acoustics design and campus planning,contributing to the creation of peaceful and comfortable campus environments.

OPTIMIZATION OF ACOUSTIC IMPEDANCE，GEOMETRIC STRUCTURE AND OPERATING CONDITION OF LINERS MOUNTED IN ENGINE DUCT

Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise reduction. Based upon the mode analysis method of sound propagation in a circular duct with multiple liners, a flexible tolerance method is used to optimize the acoustic parameters(impedance), geometric structure parameters(such as open area ratio, cavity depth and hole diameter) and operating condition parameters(such as blade passing frequency). The mathematical models for these kinds of optimization are presented here. The optimum values of the design variables are determined when the in-duct sound suppression approaches a maximum. It can be derived from the optimum results that the emphasis of the engineering optimization design of the perforated plate honey-comb structure should be placed on the optimum choice of the open area ratio and cavity depth. Some reference criteria for the engineering design of the multi-linings are also provided.

Optimization Design for the Sandwich Piezoelectric Transmitters in Acoustic Logging

An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling environments with high temperature and pressure, as well as strong collar drilling vibration during the drilling process. Aimed to improve the transmitting performance, numerical and experimental studies for the transducer optimization are conducted. The impact of location and length of the piezoelectric stack on resonance characteristics arid effective electromeehanical coupling coefficient is calculated and analyzed. Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments, and the results are compared with simulated ones. It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies. This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging, especially in acoustic logging while drilling.

Prediction of a V-8 diesel engine's structural radiated noise and research of important parameters' effects on the engine's acoustic behaviors

Based on the coupled boundary element method-finite element method （BEM-FEM） method and the acoustic transfer vector （ATV） technology, BEM/FEM model is proposed for a Vtype eight cylinders engine acoustic radiation simulating analysis under semi-anechoic condition. Acoustic radiation power, field points sound pressure level and panel contributions are calculated by acoustic radiation response analysis. Additionally, based on the engine acoustic performance, different acoustic behaviors of engine are studied by changing engine materials, oil pan structures as well as geometry parameters. The acoustic performance of this engine is predicted and the influence of material, structural and geometry parameters on engine radiated noise are generalized. The principle will guide the design and optimization of the engine prototype in further work.