A New Approach to Transient Processing in the Phase Vocoder

In this paper we propose a new method to reduce phase vocoder artifacts during attack transients. In contrast to all transient preservation algorithms that have been proposed up to now the new approach does not impose any constraints on the time dilation parameter for processing transient segments. By means of an investigation into the spectral properties of attack transients of simple sinusoids we provide new insights into the causes of phase vocoder artifacts and propose a new method for transient preservation as well as a new criterion and a new algorithm for transient detection. Both, the transient detection and the transient processing algorithms are designed to operate on the level of spectral bins which reduces possible artifacts in stationary signal components that are close to the spectral peaks classified as transient. The transient detection criterion has a close relation to the transient position and allows us to find an optimal position for reinitializing the phase spectrum. The evaluation of the transient detector by means of a hand labeled data base demonstrates its superior performance compared to a previously published algorithm. Attack transients in sound signals transformed with the new algorithm achieves high quality even if strong dilation is applied to polyphonic signals.