How to eliminate noise and the audio enhancement technologies are also proposed, especially the analyzing of the character of audio and frequency subtraction for eliminating noise.

本文详细论述了噪音消除等语音增强技术，探讨了声音特性分析及消除噪音的频谱相减算法，并且将频谱减法应用到虚拟教室模型中。

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With a phase grating located at Fourier frequency plane, optical image subtraction is obtained as a result of the coherent superposition of the zeroth and the first order of the diffracted light.

置一位相光栅于相干光学处理系统频谱平面，利用其零级与一级衍射光的相干迭加实现图象相减。

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As the mine hoist on the speed of addition and subtraction accuracy and speed requirements of high precision, variable-frequency control system must be used.

由于矿井提升机对转速精度及加减速度要求较高，必须采用高精度变频调速系统。

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