#### Eigenvalues in the Undamped Case

When , the eigenvalues reduce towhere denotes the angular advance per sample of the oscillator. Since corresponds to the range , we see that in this range can produce oscillation at any digital frequency. For , the eigenvalues are real, corresponding to exponential growth and/or decay. (The values were excluded above in deriving Eq.(C.144).) In summary, the coefficient in the digital waveguide oscillator () and the frequency of sinusoidal oscillation is simply

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