There is provided a speech decoder comprising a means for generating an excitation signal and a means for performing harmonic analysis and synthesis on the excitation signal in order to generate a smooth, periodic speech signal. The speech decoder further comprises a mixing means for mixing the excitation signal with the smooth, periodic signal and a synthesizing means for synthesizing the modified excitation signal into a speech signal that can be played to a user through a listening means. There is also provided a receiver that incorporates a speech decoder such as the decoder described above as well as a method for speech decoding.
A speech encoder comprises an encoding element for encoding a noise reduced speech signal, and a noise suppression element that takes a noisy speech signal and generates the noise reduced speech signal by maximizing the signal to noise ratio (SNR) of the noisy speech signal without suppressing the voiced speech components of the noisy speech signal. The noise suppression element may use harmonic modeling techniques that maximize the SNR in each sub-band of the noisy speech signal by reconstructing the voiced speech components of the noisy voiced speech signal emphasizing harmonic frequencies within each sub-band. The SNR is further maximized by eliminating noise components between signal peaks at the harmonic frequencies, and eliminating noise at signal peaks at the harmonic frequencies by smoothing harmonic parameters generated by the reconstruction of the voiced speech components of the noisy speech signal.
