Voice signal processing device

A cepstrum calculating device obtains a cepstrum of a voice signal and a mean-value calculation device cepstrum means output. A threshold setting device sets a voice detection threshold level on the basis of the cepstrum mean-value output. A cepstrum addition section adds a cepstrum value exceeding the cepstrum mean-value. A comparator compares the cepstrum output from the cepstrum addition section with the threshold output signal from the threshold setting device, thereby to output a voice-detection signal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a voice signal processing device with 
respect to voice detection and voice recognition techniques. 
2. Description of the Invention 
Recently, voice detection devices for detecting the presence/absence of a 
voice have been widely used for applications such as voice recognition, 
speaker recognition, equipment operation by voice, and input to computer 
by voice. 
FIG. 1 is a block diagram showing a prior art voice 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 voice-detected signal when the value is larger than 
the predetermined set value. 
According to the prior art voice detection device as described above, 
however, even if a voice input is small, when the input signal contains a 
noise other than the voice, 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. 
SUMMARY OF THE INVENTION 
The present invention intends to detect accurately voice by utilizing 
cepstrum analysis. 
A signal detection device of the present invention comprises; 
cepstrum calculating means for obtaining a cepstrum of a voice signal, 
mean-value calculation means for making equal the cepstrum output from the 
cepstrum calculating means; 
threshold setting means for setting a voice detection threshold level on 
the basis of the cepstrum mean-value output from the mean-value 
calculation means, and 
voice detection means to which the cepstrum mean-value output from the 
mean-value calculation means, the cepstrum output from the cepstrum 
calculating means and the threshold output signal from the threshold 
setting means are supplied and which detects a voice 
With a configuration according to the present invention, cepstrum 
calculation means calculates a cepstrum value of an input signal to obtain 
the calculated signal and a cepstrum mean-value signal by the calculated 
signal. Then a voice detection is performed on the basis of a signal 
exceeding the cepstrum mean-value signal, and controlled by a threshold 
signal calculated and set by the cepstrum mean-value signal. 
The present invention intends to offer such device that the processing time 
for getting a cepstrum peak is short. 
A signal detection device of the present invention comprises; 
cepstrum calculating means for calculating a cepstrum of voice input, 
peak detection means for detecting a peak of the cepstrum output from the 
cepstrum calculating means, 
analysis interval setting means for setting an analysis interval on the 
basis of the peak-detected output from the peak detection means and an 
operation mode setting signal, and 
voice detection means to which the peak-detected output from the peak 
detection means is supplied, for detecting voice, 
the peak detection interval of the peak detection means being controlled by 
the set output from the analysis interval setting means 
With a configuration according to the present invention, cepstrum 
calculation means calculates a cepstrum of a voice input to supply the 
cepstrum to peak detection means. The peak detection means detects a peak 
of the cepstrum from the cepstrum calculation means at an analysis 
interval indicated by analysis interval setting means to supply the peak 
to voice detection means. The voice detection means compares the peak from 
the peak detection means with a predetermined threshold to detect a voice. 
An operation mode and part of the peak-detected output from the peak 
detection means are inputted into the analysis interval setting means. In 
one mode of the operation mode, the analysis interval setting means 
outputs a predetermined analysis interval to the peak detection means, and 
at the same time sets an analysis interval to output under another 
operation mode in response to the peak-detected output. In another 
operation mode, the analysis interval setting means operates in a manner 
to direct the analysis interval set in the former operation mode to the 
peak detection means, thereby reducing analysis interval and shortening 
processing time. 
The present invention intend to realize a similar object as above. 
A signal detection device of the present invention comprises; 
cepstrum calculating means for calculating a cepstrum input of voice input, 
peak detection means for detecting a peak of the cepstrum output from the 
cepstrum calculating means, 
interval data setting means for setting a quefrency interval to be 
analyzed, on the basis of the peak-detected output from the peak detection 
means, 
a first memory group to which the set output from the interval data setting 
means is supplied through a first switch, 
a second memory group for setting previously interval data, 
a second switch for selecting the memory output from the plurality of 
memory groups, 
control means for controlling the first and second switches, and 
voice detection means to which the peak-detected output from the peak 
detection means is supplied, for detecting voice, 
the peak detection interval of the peak detection means being controlled by 
the output from one of the memory groups, selected by the second switch. 
With a configuration according to the present invention, in response to an 
operation mode, a control section controls whether a quefrency analysis 
interval directed to a peak detection section is to be obtained from a 
first memory or second memory, and controls whether the data from an 
interval setting section is to be stored or not in the first memory. In 
one operation mode, the control section operates in such a manner that a 
quefrency analysis interval from the second memory is directed to the peak 
detection section, and a quefrency analysis interval in response to a 
voice input is supplied from the interval setting section to and stored in 
the first memory. In another operation mode, the control section operates 
in such a manner that a quefrency analysis interval from the first memory 
is directed to the peak detection section, thereby allowing the processing 
time to be shortened. 
The present invention intends to realize a similar object as above. 
A signal processing device of the present invention comprises; 
a cepstrum calculation section for inputting therein a voice and 
calculating a cepstrum, 
a peak detection section for detecting a peak at a specified analysis 
interval, from the cepstrum, 
a voice detection section for obtaining a voice-detected output from the 
peak-detected output, 
an analysis interval setting section for calculating an optimum analysis 
interval on the basis of the peak-detected output and directing the 
specified analysis interval to the peak detection section, 
an analysis interval memory for storing an analysis interval information, 
and 
an analysis interval classification section for classifying an analysis 
interval on the basis of the optimum analysis interval and storing the 
classified analysis inteval in the analysis interval memory, 
the analysis interval directed by the analysis interval setting section to 
the peak detection section, being to be directed by the analysis interval 
classification section in response to a mode setting input, and 
the analysis interval classification section checking the optimum analysis 
interval against the contents of the analysis interval memory in response 
to the mode setting input, to direct an analysis interval on the basis of 
the checked result to the analysis interval setting section. 
With a configuration according to the present invention, a cepstrum 
calculation section calculates a cepstrum of a voice input, and supplies 
the cepstrum to a peak detection section. The peak detection section 
detects a peak of the cepstrum supplied from the cepstrum calculations 
section in accordance with an analysis interval inputted from an analysis 
interval setting section. Then, a voice detection section detects the 
presence/absence of a voice from part of the signal from the peak 
detection section to obtain a voice-detected output. Now, the interval 
setting operation of the interval setting section and the classification 
processing operation of an analysis interval classification section are 
performed in the following manner. First, when a mode setting input is 
"REGISTRATION", the analysis interval setting section supplies a 
predetermined wide analysis interval to the peak detection section, and 
calculates an optimum analysis interval in accordance with the peak of the 
cepstrum for the voice input supplied from the peak detection section, to 
supply the optimum analysis interval to the analysis interval 
classification section. The analysis interval classification section 
compares the data of the optimum analysis interval with the data of an 
analysis interval stored in an analysis interval memory, and if the both 
data are different in class from each other, stores additionally the data 
of the optimum analysis interval in the analysis interval memory. Then, 
when a mode setting input is "RECOGNITION", the analysis interval setting 
section supplies the data of tan analysis interval supplied from the 
analysis interval memory by the direction of the analysis interval 
classification section, or the set value of a predetermined wide analysis 
interval to the peak detection section, and calculates an optimum analysis 
interval in accordance with the peak of the cepstrum for the voice input 
supplied from the peak detection section to supply the optimum analysis 
interval to the analysis interval classification section. The analysis 
interval classification section selects an analysis interval similar to 
the optimum analysis interval from the memory, and directs the memory to 
supply the selected analysis interval to the analysis interval setting 
section. The above-described similar analysis intervals are defined as two 
analysis intervals whose superimposed interval is larger than a 
predetermined proportion. 
The present invention intends to detect accurately voice. 
A signal control device of the present invention comprises; 
a power calculation section for calculating a power of a signal input, 
a cepstrum calculation section for calculating a cepstrum of the signal 
input, 
a peak detection section for detecting a peak of the cepstrum from the 
cepstrum calculation section, 
an S/N calculation section for calculating an S/N ratio of the signal input 
on the basis of the output from the power calculation section and the 
output from the peak detection section, 
a signal detection section for detecting the presence/absence of a signal 
input on the basis of the output of the peak detection section, and 
control means for controlling outputting of the signal input by a logical 
product of the output from the S/N calculation section and the output from 
the signal detection section. 
With a configuration according to the present invention, 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. 
The present invention intends to offer such device operating only against 
voice input to be recognized, by detecting accurately voice by using 
cepstrum analysis. 
A signal processing device of the present invention comprises; 
a voice analysis section for analyzing a voice input and outputting an 
analyzed signal, 
a matching section for comparing the analyzed signal with a template and 
outputting a recognized signal, 
a cepstrum calculation section for calculating a cepstrum from the voice 
input and outputting the cepstrum, 
a peak detection section for detecting a peak of the cepstrum and 
outputting the peak signal, 
a voice detection section for determining the presence/absence of a voice 
by the peak signal and outputting a first control signal to the matching 
section, 
a control section for outputting a second control signal to the matching 
section in response to a mode setting input and the peak signal from the 
peak detection section, and 
a peak-value memory for storing the peak signal; and 
the control section being to write the peak signal into the peak-value 
memory in response to the mode setting input of "SETTING", and being to 
compare the peak signal of the peak-value memory with the cepstrum peak 
signal of the voice input in response to the mode setting input of 
"RECOGNITION", to output the second control signal corresponding to each 
quefrency difference of the compared results, and 
the matching section being to output the recognized output according to the 
first control signal and the second control signal. 
With a configuration according to the present invention, a cepstrum 
calculation section through a peak detection section detects a cepstrum 
peak of a voice input. Then, a voice detection section detects the 
presence/absence of a voice on the basis of the detected cepstrum peak and 
supplies a first control signal corresponding to the presence/absence of a 
voice to a matching section. Also, a control section, when a mode setting 
input is "REGISTRATION", stores the cepstrum peak signal obtained from the 
peak detection section in a peak value memory, and when a mode setting 
input is "RECOGNITION", compares the cepstrum peak signal obtained from 
the peak detection section with the peak value signal stored in the peak 
value memory and supplies a second control signal in accordance with 
respective quefrency difference to the matching section. Further, a voice 
analysis section analyzes the voice input so as to be used for the 
matching section, which in turn performs a matching processing of the 
analyzed input with a previously-registered data to obtain a recognized 
output. At that time, the initiation of the matching processing operation 
is controlled by the first and second control signals from the voice 
detection section and the control section. That is, the first control 
signal from the voice detection section, when a voice is detected, 
initiates the matching operation, while the second control signal from the 
control section initiates the matching operation where the control section 
determines, when a mode setting input is "RECOGNITION", that there is no 
difference between a quefrency of the cepstrum of the voice input and a 
quefrency of the peak signal previously registered in the memory when a 
mode setting is "SETTING". 
The present invention intends to offer such device recognizing effectively 
against only registered input among plural inputs, by detecting accurately 
voice by using cepstrum. 
A signal processing device of the present invention comprises; output using 
an analyzed output from a voice analysis section to which a voice signal 
is inputted, said matching section including first control signal 
inputting means and second control signal inputting means for controlling 
the recognition operation thereof; 
a cepstrum calculation section for calculating a cepstrum of the voice 
signal; 
a peak detection section for detecting a peak of the cepstrum at a 
specified interval and outputting the peak; 
a voice detection section for outputting a first control signal 
corresponding to the presence/absence of the voice signal from output of 
the peak detection section; 
an analysis interval memory; 
an analysis interval processing section for directing and outputting the 
analysis interval to the peak detection section, and calculating an 
optimum analysis interval corresponding to the cepstrum peak and 
outputting the interval; and 
an analysis interval classification section for classifying an analysis 
interval on the basis of the optimum analysis interval and storing the 
interval in the analysis interval memory; 
wherein the analysis interval directed to the peak detection section by the 
analysis interval processing section is to be directed by the analysis 
interval classification section in response to the mode of the mode 
setting input; the analysis interval classification section checking the 
optimum interval against the analysis interval data of the interval memory 
in response to the mode setting input, outputting the second control 
signal corresponding to the voice signal to be recognized, and classifying 
the analysis interval data of the interval memory and directing the 
analysis interval to the analysis interval processing section; wherein the 
first and second control signals limit the recognition processing in a 
manner to be performed only when a voice signal is present and to be 
recognized. 
With a configuration according to the present invention, a cepstrum 
calculation section through a peak detection section detects a peak of the 
cepstrum of a voice input signal at an analysis interval specified by an 
analysis interval processing section. A voice detection section detects 
the presence/absence of a voice on the basis of the peak of the cepstrum, 
and supplies a first control signal to a matching section. At that time, 
an analysis interval given to the peak detection section is as shown below 
according to the mode of a mode setting input. First, where the mode 
setting input is "REGISTRATION", the analysis interval processing section 
supplies a predetermined analysis interval to the peak detection section, 
and calculates an optimum analysis interval corresponding to the cepstrum 
peak to output the calculated interval to an analysis interval 
classification section. The analysis interval classification section 
performs a classification processing as shown below. That is, the analysis 
interval classification section compares the optimum analysis interval 
with an analysis interval memory, and when the interval data of the memory 
has an analysis interval containing and superimposing the optimum analysis 
interval at a proportion equal to or more than a predetermined value 
(which is defined as a similar analysis interval), supplies the similar 
analysis interval through the analysis interval processing section to the 
peak detection section, and replaces the analysis interval of the memory 
with an analysis interval composed as described below, for storing; while 
when the interval data of the memory has no similar analysis interval, the 
analysis interval classification section writes the optimum analysis 
interval into the analysis interval memory. The composed analysis interval 
contains the optimum analysis interval and a superimposed portion of the 
analysis interval given by the memory data, and the lower limit and upper 
limit of the composed analysis interval are within either of the analysis 
intervals described above. The, where the mode setting input is 
"RECOGNITION", the analysis interval processing section supplies a 
predetermined analysis interval to the peak detection section, and 
calculates an optimum analysis interval corresponding to the peak to 
output the calculated interval to the analysis interval classification 
section. The analysis interval classification section compares the optimum 
analysis interval with the analysis interval memory. At that time, when 
the analysis interval similar to the optimum analysis interval exists in 
the memory, the classification section supplies the analysis interval of 
the memory through the analysis interval processing section to the peak 
detection section, and outputs the second control signal corresponding to 
the signal to be recognized; while when no such interval exists in the 
memory, the predetermined analysis interval is held as it is for the 
analysis interval of the peak detection section. 
On the other hand, a voice analysis section analyzes the voice input 
corresponding to the analysis processing of a matching section, which in 
turn performs a matching processing of the analyzed input data with a 
previously-registered data to obtain a recognized output. At that time, 
the matching processing section is controlled such that the processing is 
performed only when the first and second control signals correspond to the 
voice signal presence and the signal to be recognized, respectively.

PREFERRED EMBODIMENTS OF THE INVENTION 
Referring to drawings, an embodiment of the present invention will be 
explained hereinafter. 
FIG. 2 shows a block diagram of a voice detection device in an embodiment 
of the present invention. With reference to FIG. 2, the configuration and 
operation of the device will be explained. A voice signal is inputted into 
a cepstrum calculation section 1 as cepstrum calculation means which in 
turn obtains a cepstrum of the signal. 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 voice detection 
section 3 as voice 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 voice detection section 3 
detects a peak of a cepstrum being equal to or more than the cepstrum 
mean-value, detects the presence/absence of a voice by the peak value, and 
when a cepstrum exceeding the cepstrum mean-value is larger than a 
threshold set value, generates a voice-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 
voice detection in the voice 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 voice 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 voice signal, 
a mean-value calculation section for calculating a mean-value of the 
cepstrum at a set-quefrency interval, a voice detection section for 
determining the peak of the cepstrum and comparing the determined value 
with a reference value to discriminate the presence/absence of a voice, 
and a threshold setting section for setting the reference value of the 
voice 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 voice detection to be 
performed with a high accuracy. 
Referring to drawings, another embodiment of the present invention will be 
explained hereinafter. 
FIG. 3 shows a block digram of a voice detection device in the embodiment 
of the present invention. 
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 voice detection device of the present 
embodiment shown in FIG. 3 together with FIG. 4 will be explained. First, 
a voice 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. 4. 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 voice-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 voice detection to be 
performed with a high accuracy. Also, setting a threshold according to the 
cepstrum mean-value allows a voice detection to be performed without 
depending to the magnitude of an input signal. 
That is, the voice 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 voice detection, with an effect that the 
dependence of the peak detection on the shape of the cepstrum peak becomes 
less, thereby allowing a voice 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 voice 
detection to be performed without depending on the magnitude of an input 
signal. 
Referring to drawings, another embodiment of the present invention will be 
explained hereinafter. 
FIG. 5 shows a block diagram of a voice detection device in an embodiment 
of the present invention, 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.sub.1 and m.sub.n are cepstrum mean-values at the interval a-b at 
the time of t.sub.1 and t.sub.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 voice 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.sub.1 at the time t.sub.1 to the cepstrum mean-value m.sub.n 
at the time t.sub.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.sub.1 to the 
value at the time t.sub.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 
from the time t.sub.l to the time t.sub.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 voice-detected signal. At that time, according to the cepstrum 
mean-value at the time from t.sub.l to t.sub.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 voice 
detection to be performed. 
As apparent by the above explanation, the present invention has a 
configuration comprising a cepstrum calculation section for calculating a 
cepstrum value from a voice signal, a mean-value calculation section for 
calculating a mean-value of the cepstrum at a set-quefrency interval, a 
voice detection section for determining the peak of the cepstrum and 
comparing the determined value with a reference value to discriminate the 
presence/absence of a voice, and a threshold setting section for setting 
the reference value of the voice 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 voice detection to be performed with a high accuracy. 
That is, the voice 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 voice 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 
voice detection to be performed. 
Referring to drawings, another embodiment of the present invention will be 
explained hereinafter. 
FIG. 7 shows a block diagram of a voice detection device in an embodiment 
of another present invention. 
According to the drawings, the configuration and operation of the device 
will be explained. First, a voice 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 voice detection 
section 74 as voice detection means compares the cepstrum peak with a 
predetermined threshold, and when detecting the input to be a voice, 
outputs a voice-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 voice 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 voice detection for the same speaker to be 
detected. Further, it will be appreciated that, even when a voice is 
temporarily superimposed by another voice-noise, the scope of the cepstrum 
peak to be detected has been narrowed down, thereby allowing an accurate 
voice detection to be performed. 
That is, apparent by the above explanation, the present invention comprises 
cepstrum calculation means for calculating a cepstrum of a voice 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 voice 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 voice is superimposed by a noise, thereby allowing a highly 
accurate voice detection to be performed and an excellent operability to 
be obtained. 
Referring to drawings, an embodiment of another present invention will be 
explained hereinafter. 
FIG. 8 is a block diagram of a voice detection device in an embodiment of 
the present invention. 
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 voice 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 voice detection section 
714 performs a voice 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 voice, 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.sub.0 
-b.sub.0 does an analysis interval previously stored in the second memory 
group 710, and the a.sub.1 -b.sub.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 voice 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.sub.0 -b.sub.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.sub.1 -b.sub.1, and stores the interval data 
a.sub.1 -b.sub.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.sub.1 -b.sub.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 voice 
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 voice 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 
present invention, the present invention 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 
present invention to obtain a similar effect to the previous present 
invention, 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 voice processing device of another 
embodiment according to the present invention. As shown in FIG. 10, a 
cepstrum calculation section 81 calculates a cepstrum of a voice 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 voice detection section 83 and the voice 
interval setting section 84. The voice detection section 83 detects the 
presence/absence of a voice from the cepstrum peak supplied from the peak 
detection section 82 to obtain a voice-detected output. The voice 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 voice 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 a 
voice by the voice detection section 83, and outputted as a voice-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 voice 
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.sub.1 and p.sub.2 indicate quefrency 
values determined by the peak detection section 82, and the intervals 
a.sub.0 -b.sub.0, a.sub.2 -b.sub.2, and a.sub.3 -b.sub.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.sub.0 -b.sub.0 for the peak detection to 
the peak detection section 82, and a cepstrum having a peak in the 
quefrency p.sub.1 indicated with solid line in FIG. 11 in response to the 
voice input, is obtained from the peak detection section 82. The analysis 
interval setting section 84 calculates the optimum analysis interval 
a.sub.3 -b.sub.3 narrower than the analysis interval a.sub.0 -b.sub.0 with 
respect to the quefrency p.sub.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.sub.3 -b.sub.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.sub.3 -b.sub.3 stored in the memory, the analysis interval 
setting section 84 supplies the predetermined interval a.sub.0 -b.sub.0 or 
a memory analysis interval wider than the a.sub.0 -b.sub.0 to the peak 
detection section 82. 
Now assuming that a cepstrum having a peak in the quefrency p.sub.1 in 
response to the voice 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.sub.3 -b.sub.3 in response 
to the p.sub.1, the analysis interval classification section 85 checks the 
presence of the analysis interval similar to the analysis interval a.sub.3 
-b.sub.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.sub.3 -b.sub.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 voice input having a peak in the quefrency p.sub.2 is 
present, the analysis interval setting section 84 calculates the optimum 
analysis interval a.sub.2 -b.sub.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.sub.0 -b.sub.0. 
According to a voice processing device of the embodiments of the present 
invention as described above, the analysis interval with a voice 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 voice 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 voice 
detection be performed. 
As apparent by the above embodiments, a signal processing device of the 
present invention 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 voice 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 voice detection 
operation is performed, allowing an accurate voice detection to be 
performed. 
Referring to FIG. 12, another embodiment of the present invention will be 
explained hereinafter. 
As shown in FIG. 12, a power calculation section 91 is supplied with a 
voice 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 voice 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 voice detection section 95. The voice 
detection section 95 detects the presence/absence of a voice 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 voice 
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 voice 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 voice detection section 95, using the cepstrum peak, detects the 
presence/absence of a voice signal, and supplies a signal indicating the 
presence/absence of a voice signal to the AND section 96. Using the voice 
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 voice 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 voice signal input 
is equal to or more than the specified value from the S/N calculation 
section 94, and obtaining a signal indicating that a voice is present in 
the voice signal input from the voice detection 95, supplies a signal for 
turning the switch 97 on to the switch 7, and allows the voice signal 
input to pass so as to obtain a voice signal output. 
According to the signal control device of the embodiment of the present 
invention as described above, an effect is obtained that a voice signal 
output is outputted only when a voice is present in the voice signal 
input, and the S/N thereof is good, so that, if the noise power of the 
voice signal input is large, the voice signal output is not outputted. 
There is also another effect that the voice signal output obtained has a 
good S/N, whereby, when the voice signal output is inputted into a voice 
recognition device and the like, a good result can be obtained. And then 
the present invention can be applied to signal other than voice 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 voice 
recognition device and the like. 
Referring to FIG. 13, a signal control device of another embodiment of the 
present invention 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 voice 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 voice 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 voice signal input. Using the cepstrum peak, the 
voice detection section 912 detects the presence/absence of a voice 
signal, and supplies a signal indicating the presence/absence of a voice 
signal to the AND section 114. Using the voice 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 voice signal input power is equal to or more 
than a specified value from the comparator 913, a signal indicating that 
the voice 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 
voice is present in the voice signal input from the voice detection 
section 912, that section supplies a signal for turning on the switch 915 
to the switch 915, allows the voice signal input to pass, and obtains a 
voice signal output. According to the embodiment of the present invention 
as described above, the voice signal output can be outputted only when a 
voice is present in the voice signal input, the S/N is good, and the power 
is sufficiently present. Accordingly, the device has an effect that a 
voice having a sufficient power and a good S/N as a voice signal output is 
obtained. Also, since the power is also detected, the input status of a 
voice can be detected, and for example, using the signal control device of 
the embodiment for voice recognition allows a signal having a good 
speaking status, in particular, a good pronunciation 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 
voice can be detected, and a signal having a good speaking status, in 
particular, a good pronunciation level of a speaker can be selected, 
thereby providing an effect that, when the signal control device of the 
present invention is used for a voice recognition device and the like, a 
good result is obtained. 
Referring to FIG. 14, another embodiment of the present invention will be 
explained hereinafter. 
FIG. 14 is a block diagram of a signal processing device in an embodiment 
of another present invention. Using FIG. 14, the configuration of the 
device will be explained below. A cepstrum calculation section 101 
calculates a cepstrum from a voice 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 
voice detection section 106. The voice detection section 106 detects the 
presence/absence of a voice 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 voice 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 voice 
analysis section 105, and the first and second control signals from the 
voice detection section 106 and the control section 103, and, in response 
to the control signals, checks the analyzed signal supplied from the voice 
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 voice 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 voice inout, and then the peak detection 
section 102 detects a peak of the cepstrum. Then, the voice detection 
section 106 detects the presence/absence of a voice by the 
presence/absence of a voice by the presence/absence of the cepstrum peak 
signal from the peak detection section 102, and when a voice is present, 
supplies the first control signal for performing matching processing to 
the matching section 107, while when a voice 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 voice detection section 106 and the control section 103 are those 
for performing matching processing, compares the analyzed signal from the 
voice 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 of the present 
invention as described above, only when the quefrency of the cepstrum peak 
of a voice 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 voice 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 voice 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 invention 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 voice input is close to a previously registered frequency, 
the matching operation can be performed, whereby there is an effect that, 
when a voice 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. 
Referring to FIG. 15, another embodiment of the present invention will be 
explained hereinafter. 
FIG. 15 is a block diagram of a signal processing device in an embodiment 
of another present invention. Using FIG. 15, the configuration of the 
device will be explained below. A cepstrum calculation section 208 
calculates a cepstrum from a voice 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 voice 
detection section 214 detects the presence/absence of a voice by the 
cepstrum peak supplied from the peak detection section 209, and supplies a 
first control signal corresponding to the presence/absence of a voice 
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 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 voice 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 voice input 
analyzed by the voice analysis section 213, and the first and second 
control signals from the voice detection section 214 and the analysis 
interval classification section 211, and, in response to the control 
signals, checks the analyzed signal supplied from the voice 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 voice input, and then the voice detection 
section 214 is supplied with the cepstrum peak, and detects the 
presence/absence of a voice. The voice detection section 214 supplies a 
first control signal to the matching section 215 in response to the 
presence/absence of a voice. 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 voice analysis 
section 213 analyzes the voice 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 voice 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 voice input, and the 
analysis interval of the cepstrum peak of the voice 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 voice 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 voice signal is registered, an 
analysis interval corresponding to a cepstrum peak corresponding to the 
pitch frequency indicating the characteristic of a voice is classified and 
stored in a memory, whereby similar voice inputs within a plurality of 
registered voice inputs correspond to a composed analysis interval and are 
stored, while the other voice inputs correspond to individual analysis 
interval and are stored. In either case, when a voice is to be recognized, 
the analysis interval corresponding to the cepstrum of an optical voice 
input is compared with the analysis interval registered in the memory, 
whereby whether the voice 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 voice 
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 voice 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 voice detection 
means to which a voice signal is inputted, and the device is provided with 
peak detection means for detecting the peak of a voice signal cepstrum 
calculated at a specified analysis interval and for outputting the first 
control signal corresponding to the presence/absence of the voice signal, 
and provided with means for classifying the analysis interval on the basis 
of an optimum interval calculated corresponding to the voice 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 voice input with the stored analysis interval in a 
recognition processing of an optional voice 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 voice 
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 
spirit and scope thereof.