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线型光束滤光片的校准
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作者 何日梅 韦秋叶 +1 位作者 范晓辉 卢敏萍 《化学分析计量》 CAS 2021年第9期63-67,共5页
建立线型光束滤光片的校准方法。采用紫外、可见、近红外分光光度计作为计量标准装置,测量线型光束滤光片在800~1100 nm波长范围内的透射比,获得线型光束滤光片的减光值。分别给出线型光束滤光片均匀性、正反差别、年变化量等参考计量... 建立线型光束滤光片的校准方法。采用紫外、可见、近红外分光光度计作为计量标准装置,测量线型光束滤光片在800~1100 nm波长范围内的透射比,获得线型光束滤光片的减光值。分别给出线型光束滤光片均匀性、正反差别、年变化量等参考计量特性要求,减光值标称值小于1.0 dB时,均匀性、正反差别、年变化量不超过±0.03 dB,减光值标称值为10 dB时,均匀性、正反差别、年变化量均不超过±0.3 dB。分析测量过程的不确定度来源,并进行不确定度评定。减光值标称值小于1.0 dB和等于10 dB的线型光束滤光片,其减光值的扩展不确定度(k=2)分别为0.06 dB和0.6 dB。该校准方法考虑了线型光束滤光片的发展现状,使线型光束滤光片的校准有据可依,可用于线型光束滤光片的校准。 展开更多
关键词 线型束滤 不确定度 减光值 均匀性 正反差别 年变化量 校准
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SPEECH ENHANCEMENT USING CONSTRAINED SPECTRAL AMPLITUDE SUBTRACTION BASED ON NONCAUSAL A PRIORI SNR 被引量:3
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作者 Wu Hongwei Wu Zhenyang 《Journal of Electronics(China)》 2006年第6期937-942,共6页
Two gain forms of spectral amplitude subtraction are derived theoretically without neglecting the correlation of speech and noise spectrum during the period of a fralne. In the implementation, the constrained gain is ... Two gain forms of spectral amplitude subtraction are derived theoretically without neglecting the correlation of speech and noise spectrum during the period of a fralne. In the implementation, the constrained gain is expressed as a function of noncausal a priori SNR (Signal-to-Noise Ratio). Noise and noncausal a priori SNR are estimated from the multitaper spectrum of the noisy signal with algorithms modified to be suitable for the multitaper spectruln. Objective evaluations show that in case of white Gaussian noise the proposed method outperforms some methods based on LSA (Log Spectral Amplitude) in terms of MBSD (Modified Bark Spectral Distortion), segmental SNR and overall SNR, and informal listening tests show that speech reconstructed in this way has little speech distortion and musical noise is nearly inaudible even at low SNR. 展开更多
关键词 Speech cnhancement Spectral amplitude subtraction Noise estimation Multitaper spectrum
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