1. A method of performing an efficient excitation quantization corresponding to a residual signal using a codebook in a speech or audio noise feedback coding (NFC) system, the NFC system including at least one noise feedback loop, the codebook including N vector quantization (VQ) codevectors, where N is an integer greater than one, the method comprising: (a) deriving N correlation values using the NFC system, each of the N correlation values corresponding to a respective one of the N VQ codevectors; (b) combining each of the N correlation values with a corresponding one of N ZERO-STATE energies of the NFC system, thereby producing N minimization values each corresponding to a respective one of the N VQ codevectors; and (c) selecting a preferred one of the N VQ codevectors based on the N minimization values, whereby the preferred VQ codevector is usable as an excitation quantization corresponding to a residual signal derived from a speech or audio signal.