The silicon vocal tract

The human vocal tract has been successfully modeled as a series of uniform cross-section tubes concatenated end-to-end. Such a model has been part of the study of the human speech generation system for many years. The similarity of the equations for sound propagation in these tubes and transmission line equations has been exploited in articulatory speech synthesis systems. Each section of tube is modeled as an RLC circuit whose element values are determined by its area and length with the current and voltage corresponding to volume velocity and pressure in the tube. With the proper vocal tract configurations, the circuit has been used as part of a speech generation system. An analog VLSI circuit is described and simulated that emulates these same equations. Spectral analysis of the simulated circuit output reveals that the first three resonance frequencies are in the same range as the corresponding human vowel formants. The silicon vocal tract will form the basis of a completely integrated analog VLSI articulatory speech synthesizer. The VLSI cylindrical section analog circuit has been designed, simulated and submitted to the MOSIS silicon foundry for fabrication in a 2 μm CMOS process