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公开(公告)号：US5278900A
公开(公告)日：1994-01-11
申请号：US680485
申请日：1991-04-04
CPC分类号： H04B3/234
摘要： A digital echo canceller has a receive path (2) and a send path (3) and comprises combining apparatus (10) for forming a send output signal [r(k)] as the difference between the signal [z(k)] applied to the send input (SI) and a replica signal [e(t)] used for cancelling an additive echo signal [e(k)] at the send input (SI) that has developed in response to a receive input signal [x(k)] applied to the receive input (RI), which echo canceller at least includes transforming apparatus (13, 15) for transforming the receive input signal [x(k)] and the send output signal [r(k)]; transforming apparatus (14) for transforming the replica signal [e(k)]; a digital adaptive filter (9) which has a number of filter coefficients for generating the replica signal [e(t)] in response to the receive input signal [x(k)] and the send output signal [r(k)], adaptation apparatus (12) for determining for each block m, adaptation components [A(p;m)] for each of the filter coefficients [W(p;m)] in response to the receive input signal [x(k)] and the send output signal [r(k)]; controllable gate means (17) for selectively passing the adaptation components [A(p;m)] to the adaptive digital filter (9); control apparatus (25-28, 21-24, 16) for determining respective levels of the send output signal [r(k)] and the receive input signal [x(k)] and for generating a control signal for the gate apparatus (17) in response to the levels thus determined, which control signals depend in a predetermined manner on the difference between the levels concerned.
摘要翻译： 数字回声消除器具有接收路径（2）和发送路径（3），并且包括用于形成发送输出信号（r（k））的组合装置（10）作为施加的信号（z（k））之间的差 用于响应于接收输入信号而产生的发送输入（SI），用于消除加性回波信号（e（k））的发送输入（SI）和复制信号（e（t））（x（ k）），该回波消除器至少包括用于变换接收输入信号（x（k））和发送输出信号（r（k））的变换装置（13,15）; 变换装置（14），用于变换复制信号（e（k））; 响应于接收输入信号（x（k））和发送输出信号（r（k）），具有用于产生复制信号（e（t））的滤波器系数的数字自适应滤波器（9） 适应装置（12），用于响应于接收输入信号（x（k））为每个块m确定每个滤波器系数（W（p; m））的适应分量（A（p; m）），以及 发送输出信号（r（k））; 用于选择性地将自适应分量（A（p; m））传递到自适应数字滤波器（9）的可控门装置（17）; 控制装置（25-28,21-24,16），用于确定发送输出信号（r（k））和接收输入信号（x（k））的各个电平，并用于产生门装置的控制信号 17）响应于如此确定的电平，哪个控制信号以预定的方式取决于所涉及的电平之间的差异。
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公开(公告)号：US4903247A
公开(公告)日：1990-02-20
申请号：US210268
申请日：1988-06-23
CPC分类号： H04B3/237 , H04M9/082 , H04B3/234 , H04B3/238 , Y10S367/901
摘要： A digital echo canceller [1] with a good protection against double-talk comprises a first filter [9] for the echo cancellation proper, a second adaptive filter [11] for making continuously adapted filter coefficients available to the first filter [9] and gate means [15] which will only apply the adapted filter coefficients to the first filter [9] if certain conditions are satisfied. In the echo canceller [1] a specific filter combination is used, in which the first filter [9] is a time-domain programmable filter (TDPF) and the second filter [11] is a frequency-domain block-adaptive (FDAF), and further means [20,20(1)] are provided that are arranged in cascade with the gate means [15] for transforming the frequency-domain filter coefficients [W(p;m)] of the FDAF [11] into time-domain filter coefficients [w(i;m)] for the TDPF [9]. These measures result in the advantages of a negligible delay in the echo cancellation by the TDPF [9], and of the possibility to improve in a simple manner the convergence behavior of the FDAF [11] and considerably reduce its computational complexity.
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公开(公告)号：US4807173A
公开(公告)日：1989-02-21
申请号：US57561
申请日：1987-06-03
CPC分类号： H03H21/00 , H03H21/0027
摘要： A frequency-domain block-adaptive digital filter (FDAF) having a finite impulse response of length N for filtering a time-domain input signal in accordance with the overlap-save method includes window means (11) for obtaining modifications (B(p;m)) of the 2N frequency-domain weighting factors (W(p;m)) from correlation products (A(p;m)). A known FDAF of this type contains five 2N-point FFT's, two of which are used in the window means (11). By utilizing a special time-domain window function which can be implemented very efficiently in the window means (11) with the aid of a frequency-domain convolution, a FDAF of this type containing only three 2N-point FFT's is obtained whose convergence properties are comparable to those of the known FDAF containing five 2N-point FFT's.
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公开(公告)号：US4637046A
公开(公告)日：1987-01-13
申请号：US487389
申请日：1983-04-21
CPC分类号： G10L25/93
摘要： A speech analysis system in which segments of digitized speech are transformed into amplitude spectrums. For the voiced/unvoiced decision use is made of the peak value or spectral intensity in each amplitude spectrum. Basically a voiced decision is made when the spectral intensity increases monotonically over several segments by more than a given factor. An unvoiced decision is made if the spectral intensity drops below a given fraction of the maximum spectral intensity in the current voiced period. Refinements in the decisions are made by the use of fixed and adaptive thresholds.
摘要翻译： 一种语音分析系统，其中数字化语音的段被转换成幅度谱。 对于有声/无声决定，使用每个幅度谱中的峰值或光谱强度。 基本上，当光谱强度在多个分段上单调增加超过给定因子时，就做出了有声的决定。 如果光谱强度低于当前有声周期中最大光谱强度的给定分数，则进行清音判定。 决策的改进是通过使用固定和适应性阈值来进行的。
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公开(公告)号：US4625327A
公开(公告)日：1986-11-25
申请号：US487390
申请日：1983-04-21
CPC分类号： G10L25/93
摘要： Speech analysis system in which segments of speech are analyzed. For the voiced/unvoiced decision use is made of the average magnitude or waveform intensity of successive speech segments. Basically a voiced decision is made when the waveform intensity increases monotonically over several segments by more than a given factor. An unvoiced decision is made if the waveform intensity drops below a given fraction of the maximum waveform intensity in the current voiced period. Refinements in the decisions are made by the use of fixed and adaptive thresholds.
摘要翻译： 分析语音分析的语音分析系统。 对于有声/无声决定，使用连续语音段的平均幅度或波形强度。 基本上，当波形强度在多个段上单调增加超过给定因子时，就做出了有声的决定。 如果波形强度低于当前有声周期中最大波形强度的给定分数，则进行清音判定。 决策的改进是通过使用固定和适应性阈值来进行的。
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