1. A voice activity detection (VAD) apparatus comprising: a receiving unit configured to receive an input audio signal; a state detector configured to determine a current working state of the VAD apparatus based on the input audio signal, wherein the VAD apparatus has at least two different working states, wherein each of the at least two different working states is associated with a corresponding working state parameter decision set (WSPDS), and wherein each WSPDS includes at least one voice activity detection parameter (VADP); a voice activity calculator configured to calculate a value for the at least one VADP of the WSPDS associated with the current working state, and to generate a voice activity detection decision (VADD) by comparing the calculated VADP value with a threshold; and an output unit configured to output the VADD.