An improved device for artificially producing speech sounds by electrical means

摘要

611,533. Secret transmission. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Feb. 28, 1946, No. 6243. Convention date, June 20, 1941. [Class 40 (iv)] In means for artificially producing speech wherein there is produced a continuous spectrum of oscillation or a train of impulses whose frequency corresponds to the fundamental frequency if the latter is present in the sound to be produced, the input from these means is supplied to a number of resonant circuits whose tuning is respectively controlled in accordance with the formants of the speech to be produced and voltages derived from these resonant circuits are separately amplified, and are combined in an amplitude ratio corresponding to the amplitude ratio of the formants. As shown, current from a microphone M passes through band-pass filters F1 ... F4 to analysers A1 to A4 and also direct to an analyser A5. The latter produces a control voltage proportional to the fundamental frequency of the sound to be transmitted. This controls an oscillator G to produce oscillations of a similar frequency in the receiver. In the case of sounds of no fundamental frequency, the absence of control voltage stops generator G, but starts generator R which gives a continuous frequency spectrum. Analysers A1 ... A4 determine the frequency and amplitude of the maximum amplitude vibration in their band and transmit voltages corresponding thereto to corresponding resonant circuits R1 ... R4 and amplifiers V ... V4. The oscillation from generators G or R pass through the resonator and amplifier pairs in parallel to the loudspeaker T. The analyser A5 is shown in Fig. 3. The oscillations are fed to a valve 4, which may actually be a chain of valves in cascade. A condenser 5 shunts part of the grid resistance in this valve with the result that the greater amplitudes in the band submitted receive greater amplification and practically pure vibrations of the frequency of the greatest amplitude are emitted. These are transformed into rectangular oscillations by valve 8 and then are transformed into voltage pulses by a condenser 11 discharged by a triggered tube 10. The analysers A ... A4 in addition have a transformer between valves 4 and 8 which is connected to a rectifier network to emit a controlling voltage proportional to the amplitude of the oscillations. Fig. 7 shows the circuit of R1 and V1. Oscillations from generators G or R are connected to terminals 208 and 209 and the frequency controlling voltage is fed to terminals 205 and 206. The valve circuit 202 is thus tuned and the modified oscillations. pass from the third winding of transformer 207 to amplifier V1. An attenuating network 216 is interposed which is controlled by the amplitude indicating voltage supplied to terminals 210 and 211. In a modification, sound is produced entirely artificially by supplying a receiving unit O with controlling voltages from a series of potentiometers controlled by manual keys.