In this letter, a robust voice activity detection (VAD) algorithm is presented. This proposed VAD algorithm makes use of the perceptual wavelet-packet transform and the Teager energy operator to compute a robust parameter called voice activity shape for VAD. The main advantage of this algorithm is that the preset threshold values or a priori knowledge of the SNR usually needed in conventional VAD methods can be completely avoided. Various experimental results show that the proposed VAD algorithm is capable of outperforming the VAD of Adaptive Multi Rate (AMR) speech codec in both additive noisy and real noisy environments.