The low frequency exhaust noise of a diesel(4 85), its generation, frequency characteristics and influencing factors have been studied through theoretic calculation, analysis and experiment.
针对柴油机（4 85 ）低频排气噪声，对其产生机理、规律及其影响因素等作了理论计算、分析及实验。
A design method for low phase noise agile X-band frequency synthesizer is presented, the theoretic analysis and calculation is performed and the test results are given.
介绍一种低相噪、捷变频x波段频率综合器设计方法，并进行理论分析、计算，最后给出测试结果。
So, it has very wide applied fields and very important theoretic meaning to study, design and develop audio-frequency measurement technique to measure audio-frequency electric parameters.
因此，研究中频电参量的测量方法，设计和开发中频范围的电参量测量仪器，不但具有广泛的应用领域，而且还具有十分重要的理论意义。
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