Abstract: A lost packet recovery device, method and computer program for a VoIP system. Lost packets containing voice information are replaced using time domain interpolation techniques. A first embodiment relies on time domain harmonic scaling to interpolate a replacement frame, using the frames that come before and after the missing frame. A second embodiment replicates a frame immediately prior to the missing frame, with an energy reduction function applied that reduces the energy level of the data samples in the frame. This replicated frame replaces the missing frame. Duplicating the prior frame and reducing its energy levels are repeated until a further frame is detected. An energy restoration function is then applied to the next available frame to gradually increase its energy level and provide for a smooth transition. Using these techniques, missing frames of voice data may be replaced to mask the effects of missing frames to a listener.