impzlength Impulse response length len=impzlength(b,a) len=impzlength(sos) len=impzlength(b,a,tol) b: Numerator coefficients. real|complex - vector|scalar a: Denominator coefficients. real|complex - vector|scalar sos: Second order estimates. real|complex - matrix (K-by-6) tol: Tolerance for estimating the effective length of an IIR filter impulse response. scalar len = impzlength(b, a, tol) returns the impulse response length for the causal discrete-time filter with the transfer function coefficients for numerator and denominator in a and b respectively. For stable IIR filters, len is the effective length impulse response length, i.e. the length after which the response is essentially zero len = impzlength(sos) returns the impulse response length of the filter specified by second order sections matrix. sos is a Kx6 matrix, where K is the number of sections. Each row of the sos matrix corresponds to a second order biquad filter len = impzlength(__, tol) specifies a tolerance for estimating the effective impulse response length in case of an IIR filter. By default, tol is 5e-5. Increasing tol leads to shorter len and vice-versa Ayush Baid