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杜比 A 降噪系统是在录音时,将声音信号通过四个滤波器(80Hz 低通、80Hz～3kHz 带通、3kHz 高通和9kHz 高通)分为四个频段。在小于5kHz 时约可取得10dB 降噪效果,然后随频率的增高,效果逐渐加大,15kHz 时达到15dB。由于一定频段内的信号只能对这一频段附近的噪声有明显的掩蔽效应。因此,分为四段后,可对整个声音信号频段都有降噪效果,并能消除噪声的喘息现象。以其中一个频段为
Dolby A noise reduction system is in the recording, the sound signal through four filters (80Hz low pass, 80Hz ~ 3kHz band pass, 3kHz high pass and 9kHz high pass) is divided into four bands. In less than 5kHz when about 10dB noise reduction effect can be obtained, and then with the frequency increases, the effect gradually increased 15dB 15dB. Since the signal in a certain frequency band can only have obvious masking effect on the noise near this frequency band. Therefore, after being divided into four segments, it can reduce the noise of the whole sound signal band and can eliminate the noise wheezing phenomenon. In one of the frequency bands