We present in this paper new methods for achieving high-quality wideband speech at low rates using the ACELP algorithm. Several innovations are introduced to optimize the quality and minimize the complexity of the coder. A multi-rate wideband speech encoding algorithm based on these techniques was recently selected by 3GPP as the standard for AMR-WB, and is currently one of the candidates for the ITU-T wideband speech coder standard at around 16 kbit/sec. This standard was jointly developed by VoiceAge and Nokia.