| 摘要 |
931,383. Vocoders. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. Nov. 30, 1961, No. 42828/61. Class 40 (4). [Also in Group XL (c)] In a vocoder system in which signals are derived which are representative of the energy in each of a number of frequency bands within the speech-frequency spectrum only signals from bands carrying more than a predetermined proportion of the total speech energy are transmitted. In addition the signals to be transmitted may be quantized into amplitude steps which are a function of the instantaneous amplitude of the total energy of the speech, the signal corresponding to the total energy being transmitted in addition to the channel signals. B and Selection. Fig. 4 shows a vocoder analyser in which only four channels are shown out of a total of say 16. Band pass filters F 1 to F 4 select portions of the speech spectrum which are rectified and filtered and the resulting channel signals applied to comparators V 1 to V 4 in which the channel signals are compared with a signal corresponding to a fraction, say 20%, of the total energy in the speech, the total energy signal being derived by filter F 20 the output of which is rectified, filtered and applied to potentiometer 20, 21. The comparator output signals, present only when the channel signal exceeds 20% of the total speech energy signal, are applied to translator 22 which gives, in known manner, index numbers to the channel signals to enable their identification at the receiver. The comparison in the comparators V 1 to V 4 may take place continuously or periodically under the control of impulser T. Amplitude quantiser, Fig. 5, quantisation of one channel only is shown, the channel signal U x being applied to comparators V 5 to V 7 in which the channel signals are compared with proportions, derived from potentiometer 23, 24, 25, 26; of the total speech energy signal U ges , the comparator output signals being multiplexed by switch 28. |
