National Free-field Sound Pressure Transformation Frequency Weighting Of The Benchmark Device Into The Algorithm And Implementation

Sound pressure metrology mainly consists of sound in air and underwater measurement. The national primary standard of sound pressure in free field is one of most important part of the national primary standard of sound pressure in air and is the highest standard in China, set for quantity dissemination, traceability and international comparison in acoustical metrology. Laboratory standard microphone is the key standard device in primary standard. Sound pressure quantity reproduction is realized by laboratory standard microphone calibration for microphone sensitivity based on reciprocity principle. Now the primary standard drops behind for its long calibration time and low automation operation, etc.To solve the mentioned problems above, this thesis researches on measurement principle and process of laboratory standard microphone. It analyzes the function and essence of voltage output control of the audio generator in measurement and puts forward a new method using dynamic frequency weighing to control generator output, replacing the function of alterable resistance box.The new method follows the same calibration principle and keep measurement device unchanged. Meanwhile, advanced analyzer in acoustic measurement is applied and measurements are more credible and effective. Comparison experiments have been performed. Experiments prove the new method with less calibration procedure and time is applicable and helpful for automatic calibration.The thesis mainly discusses following items:Chapter 1 introduces the reciprocity calibration of laboratory standard microphone, research works home and broad as well as main research works included this thesis;Chapter 2 introduces principle of sensitivity measurement for laboratory standard microphone in reciprocity calibration and measurement procedure. It also researches on output control of generator in transfer impedance measurement and provides new idea for output control of generator.Chapter 3 puts emphasis on acquirement of dynamic frequency weighing and application which used for output control for generator. It also mentions application of modern measurement and analytical instrument in calibration. Experiments and Evaluation were provided in this chapter.Chapter 4 makes the evaluation on measurement uncertainty. Chapter 5 concludes the research works and suggested some developments in the near future.