IIn accordance with an embodiment, a method of decoding an encoded audio bitstream at a decoder includes receiving the audio bitstream, decoding a low band bitstream (207) of the audio bitstream to get low band coefficients (209) in a frequency domain, and copying a plurality of the low band coefficients to a high frequency band location to generate high band coefficients (213). The method further includes processing the high band coefficients (213) to form processed high band coefficients (214). Processing includes modifying an energy envelope of the high band coefficients (213) by multiplying modification gains to flatten or smooth the high band coefficients (213), and applying a received spectral envelope decoded from the received audio bitstream to the high band coefficients (213). The low band coefficients (209) and the processed high band coefficients (214) are then inverse-transformed to the time domain to obtain a time domain output signal (215).