公开(公告)号：US4538297A

公开(公告)日：1985-08-27

申请号：US521144

申请日：1983-08-08

申请人： James Waller, Jr.

发明人： James Waller, Jr.

IPC分类号： H03G7/00 ,  H03G9/02 ,  H04B1/64

CPC分类号： H03G9/025 ,  H03G7/002

摘要： A flat frequency response compansion noise reduction system employs both input signal and control signal preemphasis and deemphasis in its encoder and decoder networks respectively. The linear range of the frequency response curve of the input signal deemphasis is selected to approximate the frequency range within the audio spectrum at which the human ear is most sensitive, typically having a high frequency end of 3.617 kHz. The frequency response curve of the input signal preemphasis is a mirror image of the frequency response curve of the input signal deemphasis. The linear range of the frequency response curve of the control signal preemphasis is selected to provide an encoder output signal having a substantially flat response. The frequency response curve of the control signal deemphasis is a mirror image of the frequency response curve of the control signal preemphasis. The amount of preemphasis is maximized to the limits of the recording medium, typically ranging from 0 db to 20 db.

摘要翻译： 平坦的频率响应压缩降噪系统分别在其编码器和解码器网络中分别采用输入信号和控制信号预加重和去加重。 选择输入信号去加重的频率响应曲线的线性范围来近似人耳最敏感的音频频谱内的频率范围，通常具有3.617kHz的高频端。 输入信号预加重的频率响应曲线是输入信号去加重的频率响应曲线的镜像。 选择控制信号预加重的频率响应曲线的线性范围以提供具有基本平坦响应的编码器输出信号。 控制信号去加重的频率响应曲线是控制信号预加重的频率响应曲线的镜像。 预加重的量最大化到记录介质的极限，通常范围从0分贝到20分贝。

公开(公告)号：US4647876A

公开(公告)日：1987-03-03

申请号：US705356

申请日：1985-02-25

申请人： James Waller, Jr.

发明人： James Waller, Jr.

IPC分类号： H03G9/02 ,  H04B1/64

CPC分类号： H03G9/025

摘要： A noise reduction system compresses an input signal at a constant ratio in response to a control signal derived from the compressed signal. Added to the derived control signal is a counterfeit control signal which causes the compressor to mistrack when the compressed signal falls below a preselected threshold level. Thus, low level compressor output signals are increasingly deemphasized. A constant counterfeit control signal produces a logarithmic decrease in compressor output signal levels below the threshold point. The resulting compressed signal is used in two ways to enhance system noise reduction. First, the compressed signal is expanded at a constant ratio over all signal levels so that low level mistracked signals are further deemphasized and the system noise floor is lowered. Second, the expanded signal is fed to a filter having a variable bandwidth controlled by a signal derived from the compressed signal and responsive to compressed signal frequency and amplitude so that the filter is desensitized to input signal amplitude changes. A multistage filter control signal arrangement may be employed to provide variable cutoffs in more than one bandwidth.

摘要翻译： 响应于从压缩信号导出的控制信号，降噪系统以恒定比例压缩输入信号。 加到导出的控制信号中的是一种假冒控制信号，当压缩信号下降到预先选择的阈值水平以下时，该控制信号使压缩器发生误差。 因此，低压缩机输出信号越来越被强调。 恒定的假冒控制信号产生低于阈值点的压缩机输出信号电平的对数减小。 所产生的压缩信号以两种方式用于增强系统降噪。 首先，压缩信号在所有信号电平上以恒定比例扩展，使得低电平失真信号被进一步降低，并且降低系统本底噪声。 第二，扩展信号被馈送到具有由从压缩信号导出的信号控制的可变带宽的滤波器，并且响应于压缩的信号频率和振幅，使得滤波器被减弱以输入信号幅度变化。 可以采用多级滤波器控制信号布置来在多于一个带宽中提供可变截止。