Method of and device for segmenting an electric signal derived from an acoustic signal
First Claim
1. A method of segmenting an electric signal derived from an acoustic signal into segments of the electric signal in which consecutivelya number of parameters is derived from the electric signal in the form of a number of signals as a function of time,the signals of the parameters located within a time interval around each instant are taken up for consecutive instants,a transition function .0. is determined for each instant from the signals of the parameters located within the time interval corresponding to said instant, andinformation relating to the segments of the acoustic signal is derived from the transition functions associated with the instants,characterized in that:
- (a) similarity factors Cij are determined, each between two transition functions (.0.i and .0.j) associated with respective proximate instants i and j, and(b) a replacing transition function is derived from the transition functions of at least one group of two transition functions for which the associated similarity factor is larger than a reference value V, the said replacing transition function replacing said transition functions from which it is derived.
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Abstract
A method and device for segmenting an electric (acoustic) signal. A number of parameters, for example "log area" parameters, are derived as a function of time from the electric signal (block 2). For consecutive instants the signals of the parameters located within a time interval around each instant are taken up and transition functions (.0.i ) are derived therefrom for each instant (block 3). Subsequently similarity factors (cij) are determined each between two transition functions (.0.i and .0.j) associated with respective proximate instants (i and j) (block 4) and a replacing transition function (.0.ijc) is derived (block 6) from the transition functions of at least one group of two transition functions for which the associated similarity factor is larger than a reference value V, the transition function (.0.ijc) replace the aforementioned transition functions from which it is derived (block 7).
A combined transition function (.0.ijc) replacing one of these transition functions is preferably calculated from the aforementioned transition functions, while the other of these transition functions are omitted. The group of transition functions for which the similarity factor is largest is preferably taken (block 5). The method is subsequently repeated (FIG. 1). Transition functions obtained are very suitable for use in the transmission or recognition of speech signals and for coding diphones.
160 Citations
18 Claims
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1. A method of segmenting an electric signal derived from an acoustic signal into segments of the electric signal in which consecutively
a number of parameters is derived from the electric signal in the form of a number of signals as a function of time, the signals of the parameters located within a time interval around each instant are taken up for consecutive instants, a transition function .0. is determined for each instant from the signals of the parameters located within the time interval corresponding to said instant, and information relating to the segments of the acoustic signal is derived from the transition functions associated with the instants, characterized in that: -
(a) similarity factors Cij are determined, each between two transition functions (.0.i and .0.j) associated with respective proximate instants i and j, and (b) a replacing transition function is derived from the transition functions of at least one group of two transition functions for which the associated similarity factor is larger than a reference value V, the said replacing transition function replacing said transition functions from which it is derived. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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7. A method as claimed in claim 4 or 5, characterized in that in step (e) the combined transition function .0.ijc is calculated from the two transition functions .0.i and .0.j in the following manner:
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space="preserve" listing-type="equation">.0..sub.ij.sup.c =(n.sub.i .0..sub.i +n.sub.j .0..sub.j)/(n.sub.i +n.sub.j)in which ni and nj indicate numbers of the original transition functions from which the transition functions .0.i and .0.j respectively are obtained by combining two transition functions in one or more previous combination steps.
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8. A method as claimed in claim 7, characterized in that a number nc which is equal to ni +nj is appended to the combined transition function, which number nc indicates from how many original transition functions the combined transition function .0.ijc has been obtained by combining two transition functions in one or more previous combination steps,
in that the number nc replaces the number (ni or nj) associated with the transition function (.0.i or .0.j) which is replaced by the combined transition function, and in that the number (nj or ni), which is associated with the one of the two transition functions that is omitted, is also omitted. -
9. A method as claimed in claim 1 or 2, characterized in that for calculating the similarity factor Cij between two transition functions .0.i and .0.j, the transition functions are considered to be vectors in a multidimensional space and in that the similarity factor is equal to the reciprocal value of the euclidic distance between ends of said vectors.
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10. A method as claimed in claim 4, characterized in that for calculating the similarity factor Cij between two transition functions .0.i and .0.j the transition functions are considered to be vectors in a multidimensional space and in that the similarity factor is equal to the cosine of the angle between the two vectors.
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11. A method as claimed in claim 10, characterized in that the said constant has a value of between 0.5 and 0.8.
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12. A device for segmenting an electric signal derived from an acoustic signal comprising:
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first means for deriving a number of parameters in the form of signals from the electric signal as a function of time, second means for deriving a transition function for each instant from the signals of the parameters located within a time interval corresponding to said instant, a first memory for storing the transition functions, third means for calculating a similarity factor between two transition functions associated with respective proximate instants i and j, a second memory for storing the similarity factors, and fourth means for deriving a replacing or combined transition function from the transition functions of at least one group of transition functions for which the associated similarity factor is larger than a reference value. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification