Abstract: A modular system and method is provided for encoding and decoding of speech signals using voicing probability determination. The continuous input speech is divided into time segments of a predetermined length. For each segment the encoder of the system computes the signal pitch and a parameter which is related to the relative content of voiced and unvoiced portions in the spectrum of the signal, which is expressed as a ratio Pv, defined as a voicing probability. The voiced portion of the signal spectrum, as determined by the parameter Pv, is encoded using a set of harmonically related amplitudes corresponding to the estimated pitch. The unvoiced portion of the signal is processed in a separate processing branch which uses a modified linear predictive coding algorithm. Parameters representing both the voiced and the unvoiced portions of a speech segment are combined in data packets for transmission.

Abstract: A signal encoding apparatus for encoding an acoustic signal. This signal encoding apparatus includes a transform circuit for transforming an inputted acoustic signal into frequency components, a signal component separating circuit for separating an output of the transform circuit into tone characteristic components and noise characteristic components, a tone characteristic encoding circuit for encoding a signal of tone characteristic components, and a noise characteristic component encoding circuit for encoding a signal of noise characteristic components, wherein the tone characteristic component encoding circuit encodes respective signal components of the signal of tone characteristic components so that they respectively have different code lengths to thereby improve efficiency of encoding without degrading sound quality with respect to acoustic signal of tone characteristic.

Abstract: A text-to-voice audio output unit includes a storage section for storing analyzed information pertaining to words, boundaries between articulations, and accents obtained by analyzing an input character list, a voice synthesis rule section for changing a reduction or damping characteristic of a phrase component of a fundamental frequency of an output voice, and a voice synthesizing section for generating a composite tone based on the analyzed information from the storage section. The reduction or damping characteristic, calculated for each phrase component, is overdamped, critically damped, or underdamped and is based on speech rate, syntactic information, number of articulations, and positional information. When a prosodic phrase is short, the reduction or damping characteristic causes a decrease in the fundamental frequency for a meaningfully-delimited portion, and when a prosodic phrase is long, the reduction or damping characteristic is controlled over the entire prosodic phrase.

Abstract: A speech decoder apparatus for synthesizing a speech signal from a digitized speech bit stream of the type produced by processing speech with a speech encoder. The apparatus includes an analyzer for processing the digitized speech bit stream to generate an angular frequency and magnitude for each of a plurality of sinusoidal components representing the speech processed by the speech encoder, the analyzer generating the angular frequencies and magnitudes over a sequence of times; a random signal generator for generating a time sequence of random phase components; a phase synthesizer for generating a time sequence of synthesized phases for at least some of the sinusoidal components, the synthesized phases being generated from the angular frequencies and random phase components; and a synthesizer for synthesizing speech from the time sequences of angular frequencies, magnitudes, and synthesized phases.