A computer-implemented method for calculating a time-domain impulse response with improved causality based on a first spectrum in a frequency domain is disclosed. The first spectrum may be band-limited. The method may calculate a first time-domain impulse response from the first spectrum. The method may remove a non-causal portion of the first system time-domain impulse response to obtain a second time-domain impulse response, and calculate a second spectrum of the second time-domain impulse response. The method may further modify the second spectrum by adding a causal signal such that a difference between the second spectrum and the first spectrum is reduced. The method may also calculate the time-domain impulse response with improved causality from the modified second spectrum.