Signal control device

Abstract: A signal control device comprises a power calculation section (91), a cepstrum calculation section (92), a peak detection section (93) for detecting a peak of said cepstrum, an S/N calculation section (94) for calculating an S/N ratio of said signal input on the basis of the calculated power and the detected peak, a signal detection section (95) for detecting the presence/absence of a signal input on the basis of the output of said peak detection section (93), and control means (96) for controlling outputting of said signal input by a logical product of the output from said S/N calculation section (94) and the output from said signal detection section (95).

Description: The present invention relates to a signal control device according to the preamble of claim 1. Recently, speech detection devices for detecting the presence/absence of speech have been widely used for applications such as speech recognition, speaker recognition, equipment operation by speech, and input to computer by speech. Fig. 1 is a block diagram showing a prior art speech detection device, whose configuration and operation will be explained hereinafter. A power detection section 19 detects a power value in an input signal to render the value to be compared by a comparator 21, and then the comparator 21 compares the value with a predetermined set value of a threshold setting section 20 to output a speech-detected signal when the value is larger than the predetermined set value. According to the prior art speech detection device as described above, however, even if a speech input is small , when the input signal contains a noise other than the speech, a power detected by the power detection section 19 larger than the set value of the threshold setting section 20, causes the voice-detected signal to be outputted, thereby developing an inconvenience of frequent erroneous detections. The article "Auswertung von Echtzeit-Cepstra zur schnellen Detektion stimmhafter Laute" of M. Timme, H. Idler und T. Lay, Nachrichtentechnische Zeitschrift, 1973, Vol. 7, pp. 112 and following teaches to use a cepstrum of a speech signal for speech recognition. The paper "A speech-to-noise ratio measurement algorithm" by J.T. Sims discloses an algorithm to measure speech-to-noise ratios. It attributes the energy within each consecutive 20 ms frame of a speech plus noise waveform to either a speech or noise source. This discrimination process is based upon the known characteristics of frame energy histograms of such waveforms. It is the object of the present invention to provide an improved method of recognizing speech signals. This object is solved in accordance with the features of the independent claims, dependent claims are directed on preferred embodiments of the invention. With a configuration according as claimed, a power calculation section calculates a power of a signal input, and a cepstrum calculation section through a peak detection section detects a peak of the calculated cepstrum. A signal detection section detects the presence/absence of a signal from the peak of the cepstrum, and when the signal is present, supplies the signal-detected signal to an AND section. Also, an S/N calculation section calculates an S/N utilizing the power of the signal input obtained by the power calculation section and the cepstrum peak from the peak detection section, and when the calculated S/N is equal to or more than a specified S/N value, supplies the calculated S/N to the AND section. The AND section operates in a manner to take a logical product of the signal from the S/N detection section and the signal of the signal detection section so as to control a switch. Accordingly, when the S/N of the signal input is good and the signal is present, the AND section operates in a manner to obtain a signal output. Fig. 1 is a block diagram of a speech detection device of prior art ; Fig. 2 is a block diagram of a speech detection device in an embodiment of related art; Fig. 3 is a block diagram of a speech detection device in another embodiment of related art; Fig. 4 is a cepstrum characteristic graph; Fig. 5 is a block diagram of a speech detection device in another embodiment of related art; Fig. 6 is a time-dependent cepstrum characteristic graph; Fig. 7 is a block diagram of a speech detection device in another embodiment of related art; Fig. 8 is a block diagram of a speech detection device in another embodiment of related art; Fig. 9 is a cepstrum characteristic graph; Fig. 10 is a block diagram of another embodiment of related art; Fig. 11 is a cepstrum characteristic graph illustrating the operation of an embodiment of related art; Fig. 12 is a block diagram of' an embodiment of the present invention; Fig. 13 is a block diagram of a similar embodiment; Fig. 14 is a block diagram of another embodiment of related art; and Fig. 15 is a block diagram of another embodiment of related art. Referring to drawings, an embodiment of the present invention will be explained hereinafter. Fig. 2 shows a block diagram of a speech detection device in an embodiment of related art. With reference to Fig. 2, the configuration and operation of the device will be explained. A speech signal is inputted into a cepstrum calculation section 1 as cepstrum calculation means which in turn obtains a cepstrum of the signal. The term "cepstrum" which is derived from the term "spectrum" is in this application symbolized by c(τ) and obtained by inverse-Fourier-transforming the logarithm of a short-time spectrum S(ω). c(τ) = m=0 M log|S(ω m )| 2 cos(τω m ) The dimension of τ is time and τ(time) is named "quefrency" which is derived from the word "frequency". Then part of the cepstrum is supplied to a mean-value calculation section 2 as mean-value calculation means which in turn obtains a cepstrum mean-value. A speech detection section 3 as speech detection means is supplied with the cepstrum from the cepstrum calculation section 1 and the cepstrum mean-value from the mean-value calculation section 2. Then, the speech detection section 3 detects a peak of a cepstrum being equal to or more than the cepstrum mean-value, detects the presence/absence of speech by the peak value, and when a cepstrum exceeding the cepstrum mean-value is larger than a threshold set value, generates a speech-detected signal. At that time, a threshold setting section 4 as threshold setting means generates a peak-value control signal having a value calculated according to a specified equation on the basis of the cepstrum mean-value from the mean-value calculation section 2, and specifies the minimum level of the speech detection in the speech detection section 3 according to the cepstrum mean-value. According to the present embodiment as described above, the device can detect accurately the peak of a cepstrum even when subjected to a noise, thereby allowing a speech detection to be performed with a high accuracy. That is, the present invention has a configuration comprising a cepstrum calculation section for calculating a cepstrum value from a speech signal, a mean-value calculation section for calculating a mean-value of the cepstrum at a set-quefrency interval, a speech detection section for determining the peak of the cepstrum and comparing the determined value with a reference value to discriminate the presence/absence of speech, and a threshold setting section for setting the reference value of the speech detection section utilizing the mean-value of the cepstrum, with an effect that the cepstrum peak can be accurately detected even under an environment having noise, thereby allowing a speech detection to be performed with a high accuracy. Fig. 3 shows a block diagram of a speech detection device in another embodiment of related art. Fig. 4 shows a cepstrum of the cepstrum calculation section 1 in Fig. 3, which is expressed with an envelope, though actually a discrete value. The configuration and operation of the speech detection device of the present embodiment shown in Fig. 3 together with Fig. 4 will be explained. First, a speech signal is inputted into a cepstrum calculation section 5 which in turn obtains a cepstrum. Then, part of the cepstrum is supplied to a mean-value calculation section 7 which in turn obtains a cepstrum mean-value level m at the quefrency interval a-b shown in Fig. 3. A cepstrum addition section 8 is supplied with the cepstrum from the cepstrum calculation section 5 and the cepstrum mean-value from the mean-value calculation section 7. Then, the cepstrum addition section 8 adds a cepstrum value being equal to or more than the cepstrum mean-value level m at a quefrency width w within the scope of the quefrency interval a-b, and supplies the cepstrum-added result to a comparator 9. The comparator 9 is supplied with the cepstrum-added result from the cepstrum addition section 8 and a set output from a threshold setting section 10, and when the cepstrum-added result is larger than the threshold set value, outputs a speech-detected signal. At that time, the threshold setting section 10 calculates a threshold according to a specified equation on the basis of the cepstrum mean-value level m shown in Fig. 4, and supplies the threshold set value to be compared with the cepstrum-added result to the comparator 9. According to the present invention as described above, the cepstrum peak can be accurately detected and the dependence on the cepstrum shape near the cepstrum peak becomes less, so that the ability of the cepstrum peak detection becomes large, thereby allowing a speech detection to be performed with a high accuracy. Also, setting a threshold according to the cepstrum mean-value allows a speech detection to be performed without depending to the magnitude of an input signal. That is, the speech detection section is allowed to have a configuration comprising a cepstrum addition section for adding cepstrum when larger than the cepstrum mean-value, and a comparator for comparing the set value from the threshold setting section with the added result from the cepstrum addition section to perform a speech detection, with an effect that the dependence of the peak detection on the shape of the cepstrum peak becomes less, thereby allowing a speech detection to be performed with a high accuracy. An effect is further obtained that the determining of a threshold set value according to the cepstrum mean-value allows a speech detection to be performed without depending on the magnitude of an input signal. Fig. 5 shows a block diagram of a speech detection device in another embodiment of related art and Fig. 6 shows a cepstrum output of a cepstrum calculation section 11. In Fig. 6, the a-b indicates a quefrency interval, the m 1 and m n are cepstrum mean-values at the interval a-b at the time of t 1 and t n , and the w is a peak detection width. Using Fig. 6, the configuration and operation of the embodiment shown in Fig. 5 will be explained. First, a speech signal is inputted into the cepstrum calculation section 11 which in turn obtains a cepstrum output. The, part of the cepstrum output is supplied to a mean-value calculations section 13 which in turn obtains a cepstrum mean-value at the quefrency interval a-b shown in Fig. 6. A memory group 17 having a plurality of n storage places is supplied with the cepstrum mean-value from the mean-value calculation section 13, stores the values from the cepstrum mean-value m 1 at the time t 1 to the cepstrum mean-value m n at the time t n shown in Fig. 6, and supplies the stored values to a cepstrum addition section 14. A memory group 16 having n-set storage places is supplied with the cepstrum output from the cepstrum calculation section 11, stores the cepstrum from the value at the time t 1 to the value at the time t n , and supplies the stored values to the cepstrum addition section 14. The cepstrum addition section 14 is supplied with the cepstrum from the memory 16 and the cepstrum mean-value from the memory 17, adds cepstrum values larger than the cepstrum mean-value at each time during from the time t 1 to the time t n and at the width w of the quefrency interval a-b shown in Fig. 6, and supplies the cepstrum-added result to a comparator 15. The comparator 15 is supplied with the cepstrum-added result from the cepstrum addition section 14 and a threshold-set value calculated by a threshold setting section 18, and when the cepstrum-added result is larger than the threshold-set value, outputs a speech-detected signal. At that time, according to the cepstrum mean-value at the time from t 1 to t n shown if Fig. 6, the threshold setting section 18 supplies the threshold-set value to be compared with the cepstrum-added result to the comparator 15. The memory groups 16 and 17 are in a condition that, when a new input is inputted into the memory groups, old data is shifted to the next storage place so that a plurality of data can always be referred in parallel. According to the present embodiment as described above, the referring of the time-dependent changes of the cepstrum peak allows a more accurate speech detection to be performed. As apparent by the above explanation, the present embodiment has a configuration comprising a cepstrum calculation section for calculating a cepstrum value from a speech signal, a mean-value calculation section for calculating a mean-value of the cepstrum at a set-quefrency interval, a speech detection section for determining the peak of the cepstrum and comparing the determined value with a reference value to discriminate the presence/absence of speech, and a threshold setting section for setting the reference value of the speech detection section utilizing the mean-value of the cepstrum, with an effect that the cepstrum peak can be accurately detected even under an environment having noise, thereby allowing a speech detection to be performed with a high accuracy. That is , the speech detection section is allowed to have a configuration comprising a first memory group consisting of n sets for storing cepstrum, a second memory group consisting of n sets for storing the cepstrum mean-value, a cepstrum addition section for adding cepstrums when larger than the cepstrum mean-value, and a comparator for comparing the set value from the threshold setting section with the added result from the cepstrum addition section to perform a speech detection, with an effect that the accumulating of data in time series on the memory groups allows the time-dependent changes of cepstrum to be detected and a more accurate speech detection to be performed. Fig. 7 shows a block diagram of a speech detection device in another embodiment of related art. According to drawings, the configuration and operation of the device will be explained. First, a speech input is inputted into a cepstrum calculation section 71 as cepstrum calculation means which in turn obtains a cepstrum. The cepstrum is supplied to a peak detection section 72 as peak detection means which in turn obtains a cepstrum peak at an analysis interval directed by an analysis setting section 73. A speech detection section 74 as speech detection means compares the cepstrum peak with a predetermined threshold, and when detecting the input to be speech, outputs a speech-detected signal. At that time, the analysis interval setting section 73 as analysis interval setting means directs an analysis interval to the peak detection section 72 and the analysis interval setting section 73 is controlled by an operation mode setting signal in a manner as described below. First, in a first operation mode, the analysis interval setting section 73 directs a predetermined quefrency analysis interval to the peak detection section 72, and sets a quefrency analysis interval which is directed to the peak detection section 72 in a second operation mode in response to the cepstrum peak obtained from the peak detection section 72. Then, in the second operation mode, the analysis interval setting section 73 directs the analysis interval having been set under the first operation mode to the peak detection section 72. The shift from the first mode to the second mode may be performed either by an operation mode setting signal of the manual operation , or by the automatic generation of the operation mode setting signal after a specified time has lapsed or a specified number of speech detection signals have been outputted. According to the present embodiment as described above, the analysis interval setting of a peak can be previously set, so that an analysis interval to determine the cepstrum peak may be narrowed down to improve processing speed. Also, the scope of the cepstrum peak to be detected is detected in the first operation mode, and narrowed down by speaker, thereby allowing an accurate speech detection for the same speaker to be detected. Further, it will be appreciated that, even when speech is temporarily superimposed by another speech-noise, the scope of the cepstrum peak to be detected has been narrowed down, thereby allowing an accurate speech detection to be performed. That is, apparent by the above explanation, the present embodiment comprises cepstrum calculation means for calculating a cepstrum of a speech input, peak detection means for detecting a peak of the cepstrum output of the cepstrum calculation means, analysis interval setting means for setting an analysis interval from the peak-detected output of the peak detection means and from an operation mode setting signal, and speech detection means to which the peak-detected output of the peak detection means is supplied, and a peak detection interval of the peak detection means is controlled by the set output of the analysis interval setting means, so that the analysis interval of the cepstrum peak can be previously set optimally, and narrowed down by shifting the mode, thereby allowing the speed of the processing for determining the cepstrum peak to be improved. Also, the narrowing down of the scope of the cepstrum peak detected according to a speaker allows an accurate voice detection to performed for the same speaker. Further, the cepstrum peak to be analyzed is narrowed down even when a speech is superimposed by a noise, thereby allowing a highly accurate voice detection to be performed and an excellent operability to be obtained. Fig. 8 is a block diagram of a speech detection device in another embodiment of related art. According to Fig. 8, the configuration and operation of the device will be explained. First, a cepstrum calculation section 75 obtains a cepstrum from a speech input, and supplies the cepstrum to a peak detection section 76. The peak detection section 76 detects the cepstrum peak from the cepstrum supplied, and is controlled such that the peak detection width of the cepstrum supplied from the cepstrum calculation section 75 is controlled using quefrency interval data obtained through a second switch 712 from an interval data memory section 711. A speech detection section 714 performs a speech detection from the cepstrum peak obtained by the peak detection section 76 on the basis of a predetermined threshold, and when detecting the input to be a speech, outputs a voice-detected signal. At that time, an interval data setting section 78 sets a quefrency interval to be detected on the basis of the cepstrum peak obtained by the peak detection section 76. The interval data set by the interval data setting section 78 is written into a first memory group 79 by turning-on of a first switch 713 by a control signal from a control section 77 in response to an operation mode. The control section 77, as described above, controls the first switch 713, and also controls the second switch 712 in response to an operation mode. The second switch 712 is controlled such that the switch is connected to the first memory group 79 when the first switch 713 is off, and is connected to a second memory group 710 when the first switch 713 is on. The interval data of the first memory group 79 and the second memory group 710 of the interval data memory section 111 are supplied through the second switch 712 to the peak detection section 76 as the analysis interval data thereof in response to an operation mode. Interval data has been previously set in the second memory group 710. Using Fig. 9, the interval data supplied to the peak detection section 76 will be explained in detail hereinafter. A cepstrum obtained by the cepstrum calculation section 75 is shown in Fig. 9, and indicated with an envelope, though actually a discrete value. The reference symbol p indicates a quefrency of the cepstrum peak, the a 0 -b 0 does an analysis interval previously stored in the second memory group 710, and the a 1 -b 1 does an analysis interval stored in the first memory group 79. For a voice input, the cepstrum peak occurs at the position of the quefrency p as shown in Fig.9. First, consider a case where, in the first mode, the second switch 712 is connected to the second memory group 710, and the first switch 713 connected to the first memory group 79. In that case, when a speech input is present, since the second switch 712 is connected to the second memory group 710, the peak detection section 76 determines the cepstrum peak in the interval data a 0 -b 0 of the second memory contents, and obtains the quefrency p of the cepstrum peak. The interval data setting section 78, using the quefrency p being the cepstrum peak obtained by the peak detection section 76, selects a value near the quefrency p to determine the interval data a 1 -b 1 , and stores the interval data a 1 -b 1 through the first switch 713 in the first memory group 79. Then, consider a case where, in the second mode, the second switch 712 is connected to first memory group 79, and the first switch 713 is off. In that case, since the second switch 712 is connected to the first memory group 79, the peak detection section 76 detects the cepstrum peak in the interval data a 1 -b 1 of the first memory described in Fig. 7. According to the present embodiment as described above, a cepstrum peak analysis interval has been previously set to be stored in the memory, so that an optimum cepstrum peak analysis interval can always be supplied, and reset to a more narrow analysis interval according to the detected result, thereby allowing processing time to be shortened, and a speech detection to be performed with high accuracy with respect to noise prevention. It will also be appreciated that, once an analysis interval has been set, the analysis interval is always valid, thereby allowing an effective speech detection processing, to be performed with an excellent operability. The memory groups are not limited to two sets, and there is no trouble even if an additional set is added as required to the groups of which a set is selectively used. That is, in place of the analysis interval setting means of the previous embodiment, the present embodiment includes the interval data setting means, a plurality of memory groups, the first switch for connecting interval data to the first memory, the second switch for selecting the interval data of the memory groups and supplying the data to the peak detection section, and the control section for controlling the first and second switches in response to the operation mode, so that the cepstrum analysis interval is narrowed down in response to a predetermined analysis interval and the input in similar manner to that of the previous embodiment to obtain a similar effect to the previous embodiment, and an increase in the number of the memory groups allows the analysis interval to be set in various ways. Fig. 10 shows a block diagram of a speech processing device of another embodiment of related art. As shown in Fig. 10, a cepstrum calculation section 81 calculates a cepstrum of a speech input, and supplies the calculated cepstrum to a peak detection section 82, and the peak detection section 82 detects a peak of the cepstrum at the analysis interval inputted from an analysis interval setting section 84, and supplies the peak to a speech detection section 83 and the speech interval setting section 84. The speech detection section 83 detects the presence/absence of a speech from the cepstrum peak supplied from the peak detection section 82 to obtain a speech-detected output. The speech interval setting section 84 calculates an optimum analysis interval in response to the cepstrum peak supplied from the peak detection section 82 and supplies the calculated interval to an analysis interval classification section 85, and further supplies analysis interval data supplied from an analysis interval memory 86 by the direction of the analysis interval classification section 85 in response to a mode setting input, or a predetermined analysis interval data to the peak detection section 82. The analysis interval classification section 85 compares the optimum analysis interval data with analysis interval data stored in the analysis interval memory 86 to perform classification processing, and stores the data in the analysis interval memory 86 in response to the mode setting input or reads the data from the analysis interval memory 86 to control the analysis interval. The operation of the device with the above configuration will be explained. A speech input is calculated for a cepstrum thereof by the cepstrum calculation section 81, then detected for a peak of the cepstrum by the peak detection section 82, then detected for the presence/absence of speech by the speech detection section 83, and outputted as a speech-detected signal. At that time, the peak detection section 82 operates in such a manner that the section 82 specifies a quefrency to determine the cepstrum peak in accordance with the analysis interval supplied from the speech interval setting section 84 to perform peak detection. Referring to Fig. 11, the operation of the analysis interval setting section 84, the analysis interval classification section 85 and the analysis interval memory 86 will be explained hereinafter. The cepstrum determined by the cepstrum calculation section 81 is shown in Fig. 11, wherein the axis of ordinate represents the level of a cepstrum and the axis of abscissa does a cepstrum. The reference symbols p 1 and p 2 indicate quefrency values determined by the peak detection section 82, and the intervals a 0 -b 0 , a 2 -b 2 , and a 3 -b 3 indicate the analysis intervals, outputted from the analysis interval setting section 84, the analysis interval memory 86 and the analysis interval classification section 85, respectively. First, when the mode setting input is "REGISTRATION" , the analysis interval setting section 84 supplies the widest analysis interval a 0 -b 0 for the peak detection to the peak detection section 82, and a cepstrum having a peak in the quefrency p 1 indicated with solid line in Fig. 11 in response to the speech input, is obtained from the peak detection section 82. The analysis interval setting section 84 calculates the optimum analysis interval a 3 -b 3 narrower than the analysis interval a 0 -b 0 with respect to the quefrency p 1 , and supplies the calculated interval to the analysis interval classification section 85. The analysis interval classification section 85 compares the optimum analysis interval with the analysis interval of the analysis interval memory 86, and when an analysis interval containing the optimum analysis interval with a proportion equal to or more than a predetermined value (which is defined as a similar analysis interval) is not present, stores the optimum analysis interval a 3 -b 3 in the analysis interval memory 86, while when the similar analysis interval is present, replaces the similar analysis interval with a composed analysis interval described below, and stores the composed interval . The composed analysis interval is an analysis interval which contains a superimposed interval of the optimum analysis interval and the memory analysis interval, and whose lower and upper limits are contained in either of the above-described intervals. Then, when the mode setting becomes "RECOGNITION" with the analysis interval a 3 -b 3 stored in the memory, the analysis interval setting section 84 supplies the predetermined interval a 0 -b 0 or a memory analysis interval wider than the a 0 -b 0 to the peak detection section 82. Now assuming that a cepstrum having a peak in the quefrency p 1 in response to the speech input as indicated with broken line in Fig. 11 is obtained from the peak detection section 82, the analysis interval setting section 84 calculates the analysis interval a 3 -b 3 in response to the p 1 , the analysis interval classification section 85 checks the presence of the analysis interval similar to the analysis interval a 3 -b 3 on the analysis interval memory 86, and since the interval is present in that case, the peak detection section 82 is supplied with the analysis interval a 3 -b 3 from the memory 86. At that time, since the analysis interval is limited to a value near the peak, the peak detection by the peak detection section 82 can be processed with a high speed. When a speech input having a peak in the quefrency p 2 is present, the analysis interval setting section 84 calculates the optimum analysis interval a 2 -b 2 , the analysis interval classification section 85 checks an interval similar to the optimum analysis interval, and since the interval is not present in that case, the analysis interval supplied to the peak detection section 82 remains the a 0 -b 0 . According to a speech processing device of the embodiments of the present invention as described above, the analysis interval with a speech by a plurality of speakers is classified into group or individual when "REGISTERED", whereby the analysis interval for the peak detection can be defined and set when recognized. Accordingly, the speech detection can be processed with a high speed, and the analysis interval is classified and defined, whereby an effective operation can be performed with respect to noise prevention when the cepstrum peak is detected, and an accurate speech detection be performed. As apparent by the above embodiments, a signal processing device of related art has a configuration comprising an analysis interval setting section for calculating an optimum analysis interval in response to the peak output of a peak detection section and supplying the analysis interval in response to a mode setting input to the peak detection section, and an analysis interval classification section for classifying the optimum analysis interval calculated by the analysis interval setting section and the analysis interval stored in an analysis interval memory for string; and has an effect that, since the speech of a plurality of speakers not limiting to individual is classified, and the analysis interval of the cepstrum peak is set by group or individual when registered, whereby the analysis interval of the cepstrum peak when recognized can be defined to perform a high-speed processing. Also, the device has another excellent effect that the analysis interval is classified into groups or individuals, whereby, even if a noise is present when the cepstrum peak is detected, an extremely good speech detection operation is performed, allowing an accurate speech detection to be performed. Referring to Fig. 12, an embodiment of the present invention will be explained hereinafter. As shown in Fig. 12, a power calculation section 91 is supplied with a speech input, calculates the power thereof, and supplies the calculated power to an S/N calculation section 94. A cepstrum calculation section 92 is also supplied with the speech input, calculates a cepstrum, and supplies the cepstrum to a peak detection section 93. The peak detection section 93 detects a peak of the cepstrum, and supplies the peak to the S/N calculation section 94 and a speech detection section 95. The speech detection section 95 detects the presence/absence of speech from the cepstrum peak of the peak detection section 93, and supplies the result to an AND section 96. The S/N calculation section 94 is supplied with the power from the power calculation section 91 and the cepstrum peak from the peak detection section 93, calculates an S/N from the supplied data, and supplies the superiority/inferiority of the calculated result to a specified value to the AND section 96. The AND section 96 is configured in a manner to take a logical product of the signals supplied from the speech detection section 95 and the S/N calculation section 94 so as to control a switch 97. The operation of the device with the above configuration will be explained. A speech signal input is calculated for the power thereof by the power calculation section 91, and detected for a peak of the cepstrum thereof through the cepstrum calculation section 92 and the peak detection section 93. The speech detection section 95, using the cepstrum peak, detects the presence/absence of a speech signal, and supplies a signal indicating the presence/absence of a speech signal to the AND section 96. Using the speech signal input power obtained from the power calculation section 91 and the cepstrum peak obtained from the peak detection section 93, the S/N calculation section 94 calculates an S/N of the speech signal input, detects whether the S/N is equal to or more than a specified value, or less than the specified value, and supplies the detected signal to the AND section 96. The AND section 96 operates such that the section 96, only when obtaining a signal indicating that the S/N of the speech signal input is equal to or more than the specified value from the S/N calculation section 94, and obtaining a signal indicating that speech is present in the speech signal input from the speech detection 95, supplies a signal for turning the switch 97 on to the switch 7, and allows the speech signal input to pass so as to obtain a speech signal output. According to the signal control device of the embodiment of the present invention as described above, an effect is obtained that a speech signal output is outputted only when a speech is present in the speech signal input, and the S/N thereof is good, so that, if the noise power of the speech signal input is large, the speech signal output is not outputted. There is also another effect that the signal output obtained has a good S/N, whereby, when the speech signal output is inputted into a speech recognition device and the like, a good result can be obtained. And then the present invention can be applied to signal other than speech signal. That is , by the above embodiment, the present invention includes an S/N calculation section for calculating an S/N with a power of a signal input and a cepstrum peak, and a signal detection section for detecting a signal from the cepstrum peak of the signal input, and has a configuration in which an AND section for taking a logical product of the S/N output from the S/N calculation section and the detected output from the signal detection section, outputs a signal to control a switch, and controls the passing of the signal input to obtain a signal output, whereby, only when a signal is present in the input, and the S/N thereof is good, the signal output can be outputted. Accordingly, an effect is obtained that, if the noise power of a signal input is large, a signal output is not outputted. There is also an effect that, since the S/N of the signal output obtained is good, a good result can be obtained when the signal output is inputted into a speech recognition device and the like. Referring to Fig. 13, a signal control device of another embodiment will be explained hereinafter. The embodiment is similar to that in Fig.12. In Fig. 13, the device is configured such that a comparator 913 compares a power from a power calculation section 98 with a reference signal input, and supplies the compared result to an AND section 114. The AND section 114 takes a logical product of signals supplied from a speech detection section 912, an S/N calculation section 911 and the comparator 913 to control a switch 915. The operation of the device having the above configuration will be explained. The power calculation section 98 calculates a power of a speech signal input, and then the comparator 913 detects whether the power is equal to or more than a specified value, or less than the specified value, and supplies the detected signal to the AND section 114. A cepstrum calculation section 99 through a peak detection section 910 detects a peak of the cepstrum of the speech signal input. Using the cepstrum peak, the speech detection section 912 detects the presence/absence of a speech signal, and supplies a signal indicating the presence/absence of a speech signal to the AND section 114. Using the speech signal input power obtained from the power calculation section 98 and the cepstrum peak obtained from the peak detection section 910, the S/N calculation section 911 calculates an S/N is equal to or more than a specified value, or less than the specified value, and supplies the detected signal to the AND section 114. The AND section 114 operates such that, only when that section obtains a signal indicating that the speech signal input power is equal to or more than a specified value from the comparator 913, a signal indicating that the speech signal input S/N is equal to or more than a specified value from the S/N calculation section 911, and further a signal indicating that a speech is present in the speech signal input from the speech detection section 912, that section supplies a signal for turning on the switch 915 to the switch 915, allows the speech signal input to pass, and obtains a speech signal output. According to the embodiment as described above, the speech signal output can be outputted only when a speech is present in the speech signal input, the S/N is good, and the power is sufficiently present. Accordingly, the device has an effect that a speech having a sufficient power and a good S/N as a speech signal output is obtained. Also, since the power is also detected, the input status of a speech can be detected, and for example, using the signal control device of the embodiment for speech recognition allows a signal having a good speaking status, in particular, a good pronounciation level of a speaker to be selected, thereby causing a better result to be obtained. That is , the device is configured in a manner to include a comparator for comparing a signal input power with a specified value and to control the switch by taking the logical product of the S/N output from the S/N calculation section, whereby, only when a signal is present in the signal input, the S/N is good, and the power is sufficiently present, a signal output can be supplied. Accordingly, the device has an effect that a signal having a sufficient power and a good S/N as a signal output is obtained. Also, since the power is also detected, the input status of a speech can be detected, and a signal having a good speaking status, in particular, a good pronounciation level of a speaker can be selected, thereby providing an effect that, when the signal control device of the present embodiment is used for a speech recognition device and the like, a good result is obtained. Fig. 14 is a block diagram of a signal processing device in another embodiment of related art. Using Fig. 14, the configuration of the device will be explained below. A cepstrum calculation section 101 calculates a cepstrum from a speech input, and supplies the cepstrum to a peak detection section 102. The peak detection section 102 detects a peak from the cepstrum, and supplies the peak to a control section 103 and a speech detection section 106. The speech detection section 106 detects the presence/absence of speech by the presence/absence of the cepstrum peak signal supplied from the peak detection section 102, and supplies a first control signal to a matching section 107. The control section 103 supplies the cepstrum peak signal supplied from the peak detection section 102 to a peak-value memory 104 according to a mode setting input, and using data supplied from the peak-value memory 104, outputs a second control signal to the matching section 107. The peak-value memory 104, which stores the cepstrum peak signal from the peak detection section 102, stores and reads data through the control section 103. A speech analysis section 105 analyzes the signal input for a data format used in the matching section 107, and supplies the analyzed signal to the matching section 107. The matching section 107 is supplied with the analyzed signal from the speech analysis section 105, and the first and second control signals from the speech detection section 106 and the control section 103, and, in response to the control signals, checks the analyzed signal supplied from the speech analysis section 105 against a template to obtain a recognized output. The operation of the device having the above configuration will be explained. First, when the mode setting input is "REGISTRATION", the cepstrum calculation section 101 calculates a cepstrum from a speech input, then the peak detection section 102 detects a peak of the cepstrum, supplies the peak to the control section 103, and then stores the peak through control section 103 in the peak-value memory 104. Then, the control section 103 supplies the second control signal for performing no matching processing to the matching section 107. Then, when the mode setting input is "RECOGNITION", similarly the cepstrum calculation section 101 calculates a cepstrum from a speech input, and then the peak detection section 102 detects a peak of the cepstrum. Then, the speech detection section 106 detects the presence/absence of speech by the presence/absence of speech by the presence/absence of the cepstrum peak signal from the peak detection section 102, and when speech is present, supplies the first control signal for performing matching processing to the matching section 107, while when speech is not present, supplies the first signal for performing no matching processing to the matching section 107. At the same time, the control section 103 compares the cepstrum peak signal from the peak detection section 102 with the contents previously stored in the peak-value memory 104, and when the quefrency values of the both are close to each other, supplies the second signal for performing matching processing to the matching section 107, while when the quefrency values of the both are not close to each other, supplies the second signal for performing no matching processing to the matching section 107. Then, the matching section 107, when the both first and second signals supplied from the speech detection section 106 and the control section 103 are those for performing matching processing, compares the analyzed signal from the speech analysis section 105 with the data of the template to perform a recognition processing operation, and outputs the result as a recognized output. According to the signal processing device in the embodiment as described above, only when the quefrency of the cepstrum peak of a speech input, that is, the pitch frequency of a speaker is close to a previously registered frequency, the matching processing with the template is performed, so that, when a speech input other than a registered speaker is inputted, the matching processing is not performed, thereby allowing the processing time required for the matching processing of the matching section to be eliminated, that is, when a speech input other than a registered speaker is inputted, a reject result is immediately outputted. Further, where the device is configured by a microprocessor and the like, the matching processing process may be held down to the minimum, whereby the CPU load can be reduced and the reduced portion be assigned to another processing process. It will be also appreciated that the outputting of a result output, as a recognized output, that the input is different from a registered speaker can be easily performed by use of the control signal of the control section 103. As apparent by the above embodiment, the present embodiment has a configuration including a control section which stores a peak signal output from a cepstrum peak detection section in a peak-value memory in response to a mode setting input, or compares the peak signal output from the cepstrum peak detection section with the peak-value memory to supply a second control signal to a matching section, so that, only when the pitch frequency of a speech input is close to a previously registered frequency, the matching operation can be performed, whereby there is an effect that, when speech other than a registered speaker is inputted, the matching processing is not performed to allow the processing process to be omitted, and a reject result is obtained with a high speed. There is also another effect that, where the device is configured by a microprocessor an the like, the matching processing process may be held down to the minimum, whereby the CPU load can be reduced and the reduced portion be assigned to another processing process, resulting in a rationalized CPU design. Fig. 15 is a block diagram of a signal processing device in another embodiment of related art. Using Fig. 15, the configuration of the device will be explained below. A cepstrum calculation section 208 calculates a cepstrum from a speech input, and supplies the cepstrum to a peak detection section 209, and the peak detection section 209 detects a peak from the cepstrum, and supplies the peak to an analysis interval processing section 210 and a voice detection section 214. The speech detection section 214 detects the presence/absence of a speech by the cepstrum peak supplied from the peak detection section 209, and supplies a first control signal corresponding to the presence/absence of a speech signal to a matching section 215. The analysis interval processing section 210 sets an optimum analysis interval in response to the cepstrum peak supplied from the peak detection section 209 and supplies the set interval to an analysis interval classification section 211, and also supplies the similar analysis interval data or a predetermined analysis interval data supplied from an analysis interval memory 212 to the peak detection section 209 in response to a mode setting input. The analysis interval classification section 211 compares the optimum analysis interval data supplied from the analysis interval processing section 210 with an analysis interval data supplied from the analysis interval memory 212, thereby to perform classification and, in response to the mode setting input, writes or reads the data to or from the analysis interval memory 212 for controlling the analysis interval, and supplies the classified result as a second control signal to the matching section 215. A speech analysis section 213 analyzes the signal input for a data format used in the matching section 215, and supplies the analyzed signal to the matching section 215. The matching section 215 is supplied with the speech input analyzed by the speech analysis section 213, and the first and second control signals from the speech detection section 214 and the analysis interval classification section 211, and, in response to the control signals, checks the analyzed signal supplied from the speech analysis section 105 against a template to obtain a recognized output. The operation of the device having the above configuration will be explained. The cepstrum calculation section 208 through the peak detection section 209 detects a cepstrum peak of a speech input, and then the speech detection section 214 is supplied with the cepstrum peak, and detects the presence/absence of speech. The speech detection section 214 supplies a first control signal to the matching section 215 in response to the presence/absence of speech. Now, the peak detection section 209 operates in a manner to detect the cepstrum peak according to an analysis interval supplied from the analysis interval processing section 210. At that time, the analysis interval supplied to the peak detection section 209 corresponds to a mode setting input as described later. The speech analysis section 213 analyzes the speech input so that the matching processing can be performed in the matching section 215. Now, consider the operation of the device in the case when the mode setting input is "REGISTRATION", and when the input is "RECOGNITION". First, when the mode setting input is "REGISTRATION", the analysis interval processing section 210 sets the analysis interval of the peak detection in the peak detection section 209 to a predetermined interval, calculates an analysis interval with a high accuracy in response to the cepstrum peak obtained from the peak detection section 209, and supplies an optimum analysis interval to the analysis interval classification section 211. The analysis interval classification section 211 checks to see if the similar analysis interval to the optimum analysis interval is present in the analysis interval memory 212, and if the interval is not present, stores newly the optimum analysis interval in the analysis interval memory 212, while if the interval is present, composes the optimum analysis interval and the similar analysis interval of the analysis interval memory 212 as described above, and replaces the contents of the analysis interval memory 212 with the composed interval for storing. Then, when the mode setting input become "RECOGNITION", the analysis interval processing section 210 supplies the data of the previously-supplied analysis interval to the peak detection section 209. The peak detection section 209 detects a peak of a cepstrum in response to a speech input, then the analysis interval processing section 210 calculates an optimum analysis interval in response to the peak, and supplies the calculated interval to the analysis interval classification section 211. The analysis interval classification section 211 checks to see if the similar interval to the optimum analysis interval supplied is present in the analysis interval memory 212, and if the interval is present, supplies the similar analysis interval ,through the analysis interval processing section 210 to the peak detection section 209 replacing the previously set analysis interval with the similar analysis interval, while if the interval is not present, holds the predetermined analysis interval, and supplies the interval to the peak detection section 209. Further, the section 211 supplies a second control signal indicating the presence/ absence of the similar analysis interval to the matching section 215. When a voice is actually present in the speech input, and the analysis interval of the cepstrum peak of the speech input is similar to a previously-registered interval as described above, the matching section 215 performs a matching operation with a template by the first control signal supplied from the speech detection section 214 and by the second control signal supplied from the analysis interval classification section 211. According to a signal processing device in the embodiment of the present invention as described above, when a speech signal is registered, an analysis interval corresponding to a cepstrum peak corresponding to the pitch frequency indicating the characteristic of speech is classified and stored in a memory, whereby similar speech inputs within a plurality of registered voice inputs correspond to a composed analysis interval and are stored, while the other speech inputs correspond to individual analysis interval and are stored. In either case, when speech is to be recognized, the analysis interval corresponding to the cepstrum peak of an optional speech input is compared with the analysis interval registered in the memory, whereby whether the speech input has been registered or not can be determined. Also, by setting an analysis interval, the analysis processing of the cepstrum peak detection is to be performed at a defined interval, thereby allowing the determination of the presence/absence of a speech input to be performed efficiently and with a high speed. Further, a noise having no cepstrum peak is removed, thereby causing an erroneous operation to be eliminated. Still further, the voice recognition processing is performed after a speech input has been efficiently confirmed and the registration thereof been confirmed as described above, thereby allowing the recognition to be performed as necessary, and the device to be efficiently used. There is also an effect that, when the device is configured by a microprocessor and the like, a processing operation without waste causes the processing load of the elements thereof to be reduced, thereby allowing many processing to be performed and the configuration to be simplified. As apparent by the above embodiment, a signal processing device of the present invention having first control signal input means and second control signal input means included in a matching section and for controlling the recognition operation of the matching section which obtains a recognition output using an analyzed output from speech detection means to which a speech signal is inputted, and the device is provided with peak detection means for detecting the peak of a speech signal cepstrum calculated at a specified analysis interval and for outputting the first control signal corresponding to the presence/absence of the speech signal, and provided with means for classifying the analysis interval on the basis of an optimum interval calculated corresponding to the speech input, storing the interval in a memory and supplying the interval to the peak detection section, the means comparing an analysis interval corresponding to an optional speech input with the stored analysis interval in a recognition processing of an optional speech input and outputting the second control signal, and the first and second control signals limiting the recognition processing in a manner to be performed only when a speech signal is present and to be recognized, whereby the recognition processing is performed as necessary, the analysis speed of the cepstrum peak detection is increased by setting an analysis interval, and a noise having no cepstrum peak is removed to cause an erroneous operation to be eliminated. Also, the recognition processing is performed as necessary, thereby allowing the device to be efficiently used. There is also an effect that a processing operation without waste causes the processing load of the device elements to be reduced, thereby allowing the configuration thereof to be simplified. It is further understood by those skilled in the art that the foregoing description is preferred embodiments and that various changes and modifications may be made in the invention without departing from the scope thereof as defined by the appended claims.

Claims: A signal control device comprising: a power calculation section (91) for calculating a power of a input signal, a cepstrum calculation section (92) for calculating a cepstrum of said input signal, and a peak detection section (93) for detecting a peak of said cepstrum from said cepstrum calculation section (92), characterized in further comprising an S/N calculation section (94) for calculating an S/N ratio of said input signal on the basis of the output from said power calculation section (91) and the output from said peak detection section (93), and for detecting whether said S/N ratio is equal to or more than a specified value, or less than the specified value, and for supplying the detected signal a signal detection section (95) for detecting the presence/absence of speech in the input signal on the basis of the output of said peak detection section (93), and control means (96) for controlling outputting of said input signal by a logical product of the output from said S/N calculation section (94) and the output from said signal detection section (95). A signal control device according to claim 1, characterized in further comprising a comparator (913) for comparing the power output of said power calculation section (98) with a reference level, wherein the control means (914) control outputting of said input signal by a logical product of the output from said S/N calculation section (911), the output from said signal detection section (912) and the output from said comparator (913). A signal control method comprising the steps of calculating a power of a input signal, calculating a cepstrum of said input signal, and detecting a peak of said cepstrum, characterized in further comprising the steps of calculating an S/N ratio of said input signal on the basis of the calculated power and the detected peak, detecting whether said S/N ratio is equal to or more than a specified value, or less than the specified value, and supplying the detected signal detecting the presence/absence of speech in the input signal on the basis of the detected peak, and controlling outputting of said input signal by a logical product of the output from said S/N calculation and detection steps and the output from said signal detection step. A signal control method according to claim 3, characterized in further comprising the steps of comparing the calculated power with a reference level, wherein outputting of said input signal is controlled by a logical product of the output from said S/N calculation and detection steps, the output from said signal detection step and the output from said comparing step.

Inventors: KANE JOJI, NOHARA AKIRA, KANE, JOJI, NOHARA, AKIRA
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: G10L11
IPC codes: G10L21, G10L11