A g l o t t a l flow model with four independent parameters is described: I t is r e f e r r e d t o as t h e LF-model. Three o f t h e s e p e r t a i n to the frequency, amplitude, and the exponential growth constant of a sinusoid. The fourth parameter is the time constant of an exponential recovery, i.e., r e t u r n phase, from t h e po in t of maximum c los ing d i s c o n t i n u i t y towards maximum closure. The four parameters are interrelated by a condition of net flow gain within a fundamental perid which is usually s e t t o zero. The f i n i t e return phase with a t i m e constant t is part ly equivalent t o a f i r s t order low-pass f i l t e r ing w i t h cutoff &equency Fa = (2TCta)-'. The LF-model is o p t i m a l for non-interactive flow parameterization i n the sense tha t it ensures an overall f i t to commonly encountered wave shapes with a minimum number of parameters and is f lexible i n its a b i l i t y t o match extreme phonations. Apart from a n a l y t i c a l l y complicated parameter interdependencies, it s b u l d l e d i t s e l f t o simple d i g i t a l implementations. The G m d e l The four-parameter model, here referred t o a s the LF-model, has developed i n two stages. The f i r s t stage was a three-parameter model of flow derivative, in t rduced by I i l jencrants. It w i l l be referred t o a s the L-model. It has the advantage of cont inu i ty whilst the early Fant (1979) model is composed of two parts, a r is ing branch: * P a e r presented a t the kench-Swedish Symposium, Grenoble, April 22-24, 1985. 1 Ug(t) = PO (1 msw t) 9 I with 6erivat ive I w u E~ (t) = 9 s i n w t 9 K+1 a r m s -jfand a descentling branch a t 5 < t < tP + Wg (3) E2(t) = -wKU sinw (t-t ) g 0 5 P This F-model has a d i scon t inu i ty a t t h e flow peak which adds a secondary weak excitation, see Fant (1979). One potential advantage of t h e L-model, Eq. ( I ) , i s t h a t it can be implemented wi th a standard second-order d ig i t a l f i l t e r with positive exponent (negative damping). The generated t i m e function is interrupted a t a t i m e te when the flow CEO Pt(as*i t CO W S Y ~ ) +U U ( t ) = 2 sl (4 a2 + w g has reached zero. The three algebraic parameters of the L-model. Eq. (I), R. a , and map on t o the three basic flow derivative parameters 1 t = W g = 2 n~~ P 2Fg ' te frcm Eq. (4) % = -%eat sinw t g e The Fand L-models share t h e parameter t o r F = 1 / 2 tp. A s P 9 shown in Fig. I. the irmodel displays a more gradual rise than the Fmodel given the constraint of equal te and E ~ / E ~ . This asymmetry increases with increasing E ~ / E ~ . The spectral d i f fe rence~ comparing the I, and F-mcdels ~e not great. The L-mcdel exhibits a lower degree of spectral ripple which is an advantage. It is convenient t o introduce the dimension-less parameters: Flow h . . . . . . c. o r . ~ * m m o . . . . . . . . . . . 0 N J . m m o 0 t Q . t . m m o