Sinusoidal model

Abstract: Sinusoidal modeling has been successfully applied to a broad range of speech processing problems, and offers advantages over linear predictive modeling and the short-time Fourier transform for speech analysis/synthesis and modification. This paper presents a novel speech analysis/synthesis system based on the combination of an overlap-add sinusoidal model with an analysis-by-synthesis technique to determine the model parameters. It describes this analysis procedure in detail, and introduces an equivalent frequency-domain algorithm that takes advantage of the computational efficiency of the fast Fourier transform (FFT). In addition, a refined overlap-add sinusoidal model capable of shape-invariant speech modification is derived, and a pitch-scale modification algorithm is defined that preserves speech bandwidth and eliminates noise migration effects. Analysis-by-synthesis achieves very high synthetic speech quality by accurately estimating the component frequencies, eliminating sidelobe interference effects, and effectively dealing with nonstationary speech events. The refined overlap-add synthesis model correlates well with analysis-by-synthesis, and modifies speech without objectionable artifacts by explicitly controlling shape invariance and phase coherence. The proposed analysis-by-synthesis/overlap-add (ABS/OLA) system allows for both fixed and time-varying time-, frequency-, and pitch-scale modifications, and computational shortcuts using the FFT algorithm make its implementation feasible using currently available hardware.

Abstract: A sinusoidal model for acoustic waveforms is applied to develop a new analysis/synthesis technique which characterizes a waveform by the amplitudes, frequencies, and phases of component sine waves. These parameters are estimated from a short-time Fourier transform. Rapid changes in the highly-resolved spectral components are tracked using the concept of "birth" and "death" of the underlying sine waves. The component values are interpolated from one frame to the next to yield a representation that is applied to a sine wave generator. The resulting synthetic waveform preserves the general waveform shape and is perceptually indistinguishable from the original. Furthermore, in the presence of noise the perceptual characteristics of the waveform as well as the noise are maintained. The method and devices disclosed herein are particularly useful in speech coding, time-scale modification, frequency scale modification and pitch modification.

Abstract: This paper presents a sinusoidal model based algorithm for enhancement of speech degraded by additive broad-band noise. In order to ensure speech-like characteristics observed in clean speech, smoothness constraints are imposed on the model parameters using a spectral envelope surface (SES) smoothing procedure. Algorithm evaluation is performed using speech signals degraded by additive white Gaussian noise. Distortion as measured by objective speech quality scores showed a 34%-41% reduction over a SNR range of 5-to-20 dB. Objective and subjective evaluations also show considerable improvement over traditional spectral subtraction and Wiener filtering based schemes. Finally, in a subjective AB preference test, where enhanced signals were coded with the G729 codec, the proposed scheme was preferred over the traditional enhancement schemes tested for SNRs in the range of 5 to 20 dB.

Abstract: The technique fits a sinusoidal model to additive vocal speech segments so that the least-mean-squared error between the model and the summed waveforms is obtained. Enhancement is achieved by synthesizing a waveform from the sine waves attributed to the desired speaker. Least-squares estimation is applied to obtain sine-wave amplitudes and phases of both talkers, based on either a priori sine-wave frequencies or a priori fundamental frequency contours. When the frequencies of the two waveforms are closely spaced, the performance is significantly improved by exploring the time evolution of the sinusoidal parameters across multiple analysis frames. The least-squared-error approach is also extended, under restricted conditions, to estimate fundamental frequency contours of both speakers from the summed waveforms. The results obtained, although limited in their scope, provide evidence that the sinusoidal analysis/synthesis model with effective parameter estimation techniques offers a promising approach to the problem of cochannel talker-interference suppression over a range of conditions. >