Spectral enhancing method and device

A method of improving decoding of an incomplete spectrum signal, said incomplete spectrum signal having been produced by encoding in a spectrum limiting manner a wide frequency band source signal, comprising enhancing the decoded signal having an incomplete spectrum which include a first spectral frequency band having an envelope by:

• performing at least one translation of the spectral content of said first frequency band into a second frequency band excluded from said spectrum by filtering the incomplete spectrum signal through a bank of analysis filters and by applying outputs signal from said bank of analysis filters to translated orders of inputs of a bank of synthesis filters to generate a translated-spectrum signal having a spectrum restricted to said second spectral frequency band,
• shaping the spectrum of the translated-spectrum signal to produce an enhancement signal and,
• adding the enhancement signal to the incomplete spectrum signal to produce an enhanced-spectrum signal,
• the generation of the translated spectrum signal including whitening said spectral content by filtering said spectral content through a whitening filter having a transfer function which is approximately inverse of an envelope function of the first spectral frequency band of the incomplete spectrum, wherein said transfer function is based on information indicative of the spectral envelope of the incomplete-spectrum signal comprising LPC coefficients of the incomplete-spectrum signal so the spectrum of the translated spectrum signal is a whitened version of said spectral content.