| 摘要 |
<p>ECHO DETECTOR PARTICULARLY FOR SPEECH INTERPOLATION COMMUNICATION SYSTEMS An echo detector which is able to distinguish a speech signal echo on the outgoing channel without reference to the signal received at the incoming channel. The echo detector is comprised of a circuit for digital differential coding in which the error signal between the incoming signal and the predicted signal is divided by the average value of a certain number of samples of previously received incoming signals, having sign according to the second-last received sample, the quotient obtained in this first division being again divided by the average value of a certain number of such quotients previously computed, the logarithm to base 2 of the average value for the entering signal samples and the logarithm to base 2 of the average value of the quotients, for which only the integer portion is kept, forming for each treated sample two values defining one point of a matrix of points, a first counter counting for a number of sets of two values for which the corresponding points are above or on the secondary diagonal of the matrix, a second counter counting simultaneously the number of sets of values for which the corresponding points are below or on the above-mentioned secondary diagonal, a divider carrying out the quotient of the counts from the first and the second counter, this quotient being compared to a predetermined value to decide, if it is greater than this value, that the entering signal is an echo and not a direct signal.</p> |
