Hello..........!
I want to simulate the artificial speech production system in labview which will be helpful for the people who have lost their ability to speak due to laryngeal cancer or laryngectomy.
while searching through net i got the following circuit i want to know if it is possible to simulate this using labview, if so please help me otherwise please anyone can suggest me the other circuit for the artificial speech production system.? I am giving here the circuit as well as the description please provide me the block diagram and front panel of the system. please help me.
The vocal tract is represented 'as a non uniform transmission line supporting longitudinal propagation only. Its characteristic impedance at all points is inversely proportional to the cross sectional area in a plane perpendicular to the flow line . The tract is assumed hardwalled ; the compliance of the soft tissues of the tract wall is ignored. The sampling frequency for the
simulation , 24 kHz, is determined by the spacing of area samples, 1.5 cm, that is necessary to simulate the continuous tract up to a signal frequency of 6 kHz. Since the length of each section is considerably smaller than the wavelength even at this frequency, the effect of the distributed reflection of a section traversed by the wavefront in one sampling period can be represented by a lumped reflection coefficient centered on the section.Figure 1 shows a block diagram of the v o c a l - t r a c t model. Pressure samples propagate back and forth along the transmission line and suffer multiple internal reflections . E x c i t a t i o n may be p e r i o d i c, simulating vocal-cord vibration , or turbulent corresponding to frication . For per i o d i c e x c i t a t i o n the samples of the excitation function are added to the samples of the r e f l e c t e d signal arriving at the glottis . Turbulent excitation may take place at the vocal cords or at any interior section . It is Implemented by means of a white - noise generator and associated source impedance placed in series with the line . For computational simplicity , the tract is assumed lossless within its interior . Simple digital filters act at the tract boundaries, the vocal cords and the lips , to approximate the frequency-dependent losses so that actually measured resonant-frequency bandwidths are properly matched. The glottal reflection and the labial radiation functions act essentially as high-pass filters ; the labial reflection appears as a lowpass filter . The nasal passage is represented by an additional transmission line of fixed but nonuniform shape coupled to the main tract with the aid of a variable coupling parameter. It serves in the production of nasalized vowels and consonants. The system output is obtained by summing the outputs of digital filters approximating the free-space radiation characteristics at the lips and nostrils . Radiation through the lips is , of course, controlled by the variable lip area. If the opening is reduced, more of the energy arriving at the lips is reflected within the tract and less is radiated to the outside . Radiation through the tract wall is not explicitly included. Articulatory movement is simulated by defining a sequence of articulatory states or targets and interpolating the position -dependent reflection coefficient values and oral - nasal coupling between them. Thus targets are not necessarily phonemic in nature but may be specified as frequently as desired in order to approximate natural articulatory movement as closely as possible . When the articulator positions are derived from a model of articulatory activity , the vocal - tract shapes computed therefrom are expected to act as the target states of the simulation program. Stress and intonation information are assumed embedded in the excitation frequency and amplitude parameters and will not be discussed here in detail . Linear interpolation of the reflection - coefficient values implies that near sharp constrictions the area varies linearly with time, but where the area changes slightly or the reflections are small, the areas vary exponentially with time. The resonant-frequency curves resulting from this procedure resemble those observed in spectrograms more closely than the straight -line segments used in most formant synthesizers.
