Engine noise source identification is essential for making noise reduction strategies.Predominant noise sources of engines are normally identified as some cover components such as oil pan, valve cover and front gear c...Engine noise source identification is essential for making noise reduction strategies.Predominant noise sources of engines are normally identified as some cover components such as oil pan, valve cover and front gear cover etc. The radiated noise sources of a 6-cylinder construction diesel engine are identified with two methods-lead covering technique and surface vibration technique,and the ranking of the major cover on the basis of acoustic power is presented in this paper. Firstly the sound power level of these cover components and their contributions to the total acoustic power are determined with lead covering method under hemi-anechoic condition. Then the vibration characteristics of these components are investigated. The sound power level of various components is predicted via the mean square area average vibration. Both results basically agree well and verify the effectiveness of both techniques in engineering field.展开更多
A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） pro...A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） process and is excited in the Lain6 mode with electrostatic driving and capacitive sensing. The Lam6 mode may be described as a square plate that is cont- racting along one axis in the fabrication plane, while simultaneously extending along an orthogonal axis in the same plane. The microresonator exhibits a quality factor as high as 1.4 × 10^6 and a resonant frequency of 4.13 MHz at a pressure of 0.08 mbar. The output spectrum of the oscillator shows that the silicon micromechanical resonator is adapted as a timing element for a precision oscillator.展开更多
This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well a...This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.展开更多
文摘Engine noise source identification is essential for making noise reduction strategies.Predominant noise sources of engines are normally identified as some cover components such as oil pan, valve cover and front gear cover etc. The radiated noise sources of a 6-cylinder construction diesel engine are identified with two methods-lead covering technique and surface vibration technique,and the ranking of the major cover on the basis of acoustic power is presented in this paper. Firstly the sound power level of these cover components and their contributions to the total acoustic power are determined with lead covering method under hemi-anechoic condition. Then the vibration characteristics of these components are investigated. The sound power level of various components is predicted via the mean square area average vibration. Both results basically agree well and verify the effectiveness of both techniques in engineering field.
文摘A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） process and is excited in the Lain6 mode with electrostatic driving and capacitive sensing. The Lam6 mode may be described as a square plate that is cont- racting along one axis in the fabrication plane, while simultaneously extending along an orthogonal axis in the same plane. The microresonator exhibits a quality factor as high as 1.4 × 10^6 and a resonant frequency of 4.13 MHz at a pressure of 0.08 mbar. The output spectrum of the oscillator shows that the silicon micromechanical resonator is adapted as a timing element for a precision oscillator.
文摘This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.
