Method of boundary estimation for voice recognition and voice recognition device

A voice recognition device including

• a feature extracting means for analyzing an input voice and converting into a feature parameter of time series;
• a boundary detecting means for detecting a region of a phonemic boundary or a neighborhood of the phonemic boundary in the input voice from the feature parameter of time series, the boundary detecting means first comparing a probability that the phonemic boundary or the neighborhood of the phonemic boundary exists within a window having a predetermined time width to a probability that the phonemic boundary or the neighborhood of the phonemic boundary does not exist within the window and comparing a result of the first comparison to a threshold having a value that varies dependent on a particular type of phonemic boundary that is detected;
• a model calculating means in which a time of producing each boundary of a plurality of phonemic model series is limited within a region of the phonemic boundary or the neighborhood of the phonemic boundary which the boundary detecting means detects when preparing the model series, the phonemic model series being prepared corresponding to the feature parameter;
• and
• a phonemic series converting means for selecting a suitable phonemic model series corresponding to the input voice from a result of the model calculating means.

A method of producing a signal representing an estimate of the presence at a time location in a voice signal of a phonemic boundary comprising the steps of:

• receiving the voice signal into an analysis system;
• analyzing the voice signal to produce a parametric voice signal representing the voice signal as a time series of parameter groups;
• extracting as a sample each parameter group within a variable position window of a predetermined time width;
• calculating for the sample extracted at each position of the window a common probability density which represents a probability that the phonemic boundary lies at a center of the window;
• calculating a first probability density estimating whether a particular boundary type lies at the center of the window, by multiplying the common probability density calculated by a first polynomial coefficient;
• calculating a second probability density estimating whether the particular boundary type does not lie at the center of the window, by multiplying the common probability density calculated by a second polynomial coefficient;
• and
• producing a signal indicative of the estimate of the presence of the phonemic boundary as a function of the first and second probability densities.

A method of producing a signal representing an estimate of the presence at a time location in a voice signal of a phonemic boundary comprising the steps of:

• receiving the voice signal into an analysis system;
• analyzing the voice signal to produce a parametric voice signal representing the voice signal as a time series of parameter groups;
• extracting as a sample each parameter group within a window of a predetermined time width, the window centered at a time location;
• calculating from the time series of parameter groups a probability that a phonemic boundary lies at the time location;
• multiplying the probability calculated by a first polynomial coefficient to form a probability that a particular type of phonemic boundary lies at the time location;
• multiplying the probability calculated by a second polynomial coefficient to form a probability that the particular type of phonemic boundary does not lie at the time location;
• and
• producing a signal indicative of the estimate of the presence of the phonemic boundary as a function of the first and second probability densities.

Apparatus for estimating a likelihood of presence of a phonemic boundary at a time location within a voice signal, comprising:

• a voice signal analyzing device having an input receiving the voice signal, having an output carrying a parametric voice signal, the voice analyzing device producing the parametric voice signal as a time series of parameter groups;
• a segment extraction device connected to receive from the voice signal analyzing device the parametric voice signal, and producing at an output a signal representing a segment of the voice signal including a time series of parameter groups falling within a variable position window of a predetermined time width, the window having a center at a time location;
• a first probability calculating device, receiving the segment of the voice signal from the segment extraction device and producing an output signal representing a probability that the phonemic boundary lies at the time location;
• a second probability calculating device, receiving the probability from the first probability calculating device, and multiplying the probability received by a first polynomial coefficient to produce a signal indicative of likelihood of presence of a particular type of phonemic boundary at the time location;
• a third probability calculating device, receiving the probability from the first probability calculating device, and received by a second polynomial coefficient to produce a signal indicative of likelihood that a particular type of phonemic boundary does not lie at the time location.