GB1227578A - - Google Patents

Abstract

1,227,578. Vocoders. INTERNATIONAL BUSINESS MACHINES CORP. 29 July, 1968 [3 Aug., 1967], No. 36005/68. Heading H4R. In an arrangement for the production of synthetic speech from stored data a first store, VOL, Fig. 1, stores in digital form the transient responses of a number of vocoder synthesizer filters a second store, AG1, stores the aggregate function signals, also in digital form, and the corresponding quantities in the two stores are multiplied together and summed to provide a digital representation of the spectral characteristics of the synthetic speech which is inserted into a third store AG1 from which it is released at the appropriate time under the control of excitation function signals stored in a fourth store EXL. As described the aggregate and excitation function signals are those of 50 speech channels in time multiplex which are all reconstituted using the same synthesis filter characteristics and distributed, by switches S1 &c., to the appropriate output lines L 1 to Lm. Fig. 2, showing the synthesizer in more detail, comprises the filter response delay line store VOL in which the responses of sixteen synthesis filters are each stored as 50 scanning points of 4 digits each, stored as sixteen groups of four followed by eight blank digits for synchronization for each scanning point. The aggregate function signals for fifty speech channels are stored in delay line store AGL and the system is organized so that each aggregate function value, stored as four bits, is multiplied by the appropriate filter response value in multiplier MULT and the groups of sixteen products, representing the outputs of the sixteen channels at an instant of time corresponding to one of the fifty scanning points of the filter responses, are summed in adder AD1 and fed into an appropriate one of the stores AG1 to AG50, appropriate to the speech channel from which the aggregate function signals originated. The excitation function is stored in recirculating delay device EXL from which groups of 8 digits representing an excitation function value plus one spacing digit are available at storage position Z to control the feeding of the aggregate function values from the stores AG1-50 into the corresponding lines VL1-50 at appropriate times dependent on the value of the excitation function.