JP6157201B2 - Apparatus, program, and method for detecting specific frequency corresponding to code from voice signal including noise - Google Patents

Description

  The present invention relates to a technique for detecting a DTMF (Dual Tone Multi-Frequency) signal from an audio signal.

In the old days, there is a technique for transmitting and receiving a DTMF signal via a telephone (voice) line for a communication terminal such as a facsimile machine or a personal computer. The DTMF signal is a signal sound assigned to each button in, for example, a tone (push) type telephone. In this case, two types of sounds with specific frequencies are transmitted with respect to one button. Generally, one sound is combined from each of four types of specific frequencies of low group tones and four types of specific frequencies of high group tones.
Low group tone: 697 Hz, 770 Hz, 852 Hz, 941 Hz
High group tone: 1209 Hz, 1336 Hz, 1477 Hz, 1633 Hz
For example, the DTMF signal indicating the dial “6” is composed of a 770 Hz tone and a 1477 Hz tone.

  The DTMF signal is not limited to transmission of a telephone number for making a call, but is also used for transmitting and receiving a control code after a voice call is established. The control code is, for example, an alphanumeric character, and the alphanumeric character can be detected from an audio signal including a DTMF signal. Such a communication terminal is equipped with a DTMF signal detector. Also, there is an apparatus for detecting a DTMF signal included in an audio signal that is input from the outside by a microphone and is not limited to an audio signal received via a telephone line. There is also a technique for transmitting a control code converted into a DTMF signal to a device located at a remote place via a telephone line and operating the device remotely (see, for example, Patent Document 1).

  FIG. 1 is a functional configuration diagram of a DTMF signal detector in the prior art.

  According to FIG. 1, the DTMF signal detector has eight rows of circuit sequences for each of eight types of specific frequencies including the high group tone and the low group tone. Each circuit series for each specific frequency includes a bandpass filter, a multiplier, a lowpass filter, a level detector, and a coder (encoder). The band-pass filter passes only a frequency band having a predetermined width with the specific frequency as the center, and outputs it to the multiplier. The multiplier squares the signal and outputs it to the low-pass filter. The low-pass filter smoothes the signal and outputs it to the level detector. The level detector detects the level of the signal and outputs the level to the coder. The coder detects a combination of high group tones and low group tones from a signal output from each circuit series for each specific frequency, and outputs a code corresponding to the combination. Of course, a frequency analyzer such as a fast Fourier transform may be used instead of the bandpass filter. In other embodiments, it is not necessary to use a smoothing low-pass filter.

  In general, the DTMF signal detector is equipped with various functions in order to avoid erroneous detection due to the influence of noise other than the DTMF signal.

  Conventionally, there is a technique for comparing power outside the DTMF frequency band, power in a high group frequency band within the DTMF frequency band, and power in a low group frequency band within the DTMF frequency band (for example, Patent Documents). 2). This comparison is based on the difference between the power of a specific frequency of the DTMF signal and the power of a band other than the specific frequency of the DTMF signal. Therefore, in addition to the power measuring unit of a specific frequency used for detecting the DTMF signal, a power measuring unit of a band other than the specific frequency of the DTMF signal is separately required.

  There is also a technique for comparing the power of the entire band, the power of a high group of frequency bands within the DTMF detection frequency band, and the power of a low group of frequency bands within the DTMF detection frequency band (see, for example, Patent Document 3). Further, there is a technique for comparing the power of the entire band, the power of the high group tone signal, and the power of the low group tone signal (see, for example, Patent Document 4). This comparison is based on the difference between the power of a specific frequency of the DTMF signal and the power of the entire band (including the specific frequency of the DTMF signal). Therefore, when the difference between them is smaller than the predetermined threshold, it is determined that the input signal is not a DTMF signal, thereby reducing erroneous detection of the DTMF signal. That is, when the power of the band other than the specific frequency of the DTMF signal is high, the detection of the DTMF signal is suppressed. Therefore, the power of a specific frequency of the DTMF signal is not taken into consideration, and detection is always suppressed when noise in other bands is large.

There is also a technique for reducing false detection of a DTMF signal by determining that the input signal is not a DTMF signal using the following three values in each of the four high group tones and the four low group tones. Yes (see, for example, Patent Document 5).
-A value that compares the power of the maximum tone signal and the total power of the four tone signals-Number of signals whose power exceeds the threshold among the four tone signals-Power of the maximum tone signal and the second largest tone Value compared with signal power

  Any of the above-described conventional techniques is intended to suppress erroneous detection of a DTMF signal due to the influence of noise or the like even though the DTMF signal is not transmitted. That is, when a noise signal is included in a band other than the specific frequency corresponding to the DTMF signal, the detection of the DTMF signal is suppressed.

JP 2000-196768 A Japanese Patent No. 2853841 Japanese Patent No. 2853842 Japanese Patent No. 2856968 Japanese Patent No. 2551974 Japanese Patent Laid-Open No. 2001-112033 Japanese Patent Laid-Open No. 5-284213

  However, according to any of the above-described conventional techniques, when noise is mixed in an audio signal, the number of cases in which a DTMF signal is not detected increases despite the fact that the DTMF signal is transmitted. In particular, according to the technique described in Patent Document 1, a communication terminal utters a DTMF signal received via a telephone line as it is from a speaker and receives the sound by a microphone. Therefore, the air between the speaker and the microphone is affected by noise. The problem is that the DTMF signal is disturbed by noise and cannot be converted into an appropriate control code.

  FIG. 2 is a graph showing the power with respect to the frequency component of the DTMF signal in the prior art.

  FIG. 2A shows a case where there is no noise, and high power is detected for frequency components of 770 Hz and 1477 Hz in the transmitted DTMF signal. Therefore, the code “6” is detected from the combination of 770 Hz and 1477 Hz.

  On the other hand, FIG. 2 (b) shows the case where noise is mixed in the audio signal, and the power of other frequency components is higher than the frequency components of 770Hz and 1477Hz in the transmitted DTMF signal. Will be detected. Therefore, the combination of 770 Hz and 1477 Hz cannot be detected.

  Therefore, an object of the present invention is to provide an apparatus, a program, and a method that can detect a specific frequency corresponding to a code as much as possible even for an audio signal including noise.

According to the present invention, a specific frequency is preassigned for each code, and in the device for detecting a code of a specific frequency included in the audio signal,
For each code, a specific frequency band including the specific frequency is preset,
Frequency analysis means for detecting the power of the frequency component in each specific frequency band for each code from the audio signal;
In each specific frequency band for each code, a maximum determination that determines whether or not the power in the specific frequency band is “maximum” relative to the power in other frequency bands around both sides of the specific frequency band Means,
A specific frequency detecting means for detecting a specific frequency having the maximum power in one or more specific frequency bands determined to be maximal; a code output means for outputting a code associated with the detected specific frequency; I have a,
The specific frequency band and the other frequency bands around both sides of the specific frequency have a frequency resolution of Fourier transform based on a sampling frequency .

According to another embodiment of the device of the invention,
It is also preferable that the specific frequency detecting unit detects only the specific frequency at which the power is maximum when the power is equal to or greater than a predetermined threshold.

According to another embodiment of the device of the invention,
For each code, a plurality of different specific frequencies are combined,
The specific frequency detecting means detects a plurality of specific frequencies where the power is maximum,
The code output means preferably outputs a code associated with a combination of a plurality of detected specific frequencies.

According to another embodiment of the device of the invention,
The specific frequency is DTMF (Dual-Tone Multi-Frequency)
For each code, a specific frequency band centered on each specific frequency is set in advance for each of the high group tone and the low group tone,
For each of the high group tone and the low group tone, the local maximum judging means is configured such that, in each specific frequency band for each code, the power in the specific frequency band is higher than the power in other frequency bands around both sides of the specific frequency band. To determine whether it will be “maximum”,
The specific frequency detecting means detects a specific frequency at which the power is maximum in one or more specific frequency bands determined to be maximum for each of the high group tone and the low group tone,
The code output means preferably outputs a code associated with the specific frequency detected with the high group tone and the specific frequency detected with the low group tone.

According to another embodiment of the device of the invention,
The specific frequency detection means is
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from one or more specific frequency bands determined to be maximum,
It is also preferable to detect the specific frequency only when the power value of each specific frequency band selected for each of the high group tone and the low group tone is equal to or greater than a predetermined threshold.

According to another embodiment of the device of the invention,
The specific frequency detection means is
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from one or more specific frequency bands determined to be maximum,
Compare the power value of each specific frequency band selected for each of the high group tone and the low group tone with the average power value of the other specific frequency bands not selected by combining the high group tone and the low group tone, It is also preferable to detect the specific frequency only when the difference is greater than or equal to a predetermined threshold.

According to another embodiment of the device of the invention,
The specific frequency detection means is
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from one or more specific frequency bands determined to be maximum,
The power value of the specific frequency band selected for the high group tone is compared with the average power value of the other specific frequency band not selected for the high group tone, and the difference is equal to or greater than a predetermined threshold value,
Only when the power value of the specific frequency band selected for the low group tone is compared with the average power value of the other specific frequency bands not selected for the low group tone, and the difference is equal to or larger than a predetermined threshold value, It is also preferable to detect the specific frequency.

According to the present invention, a specific frequency is preassigned for each code, and in a program for causing a computer mounted on a device that detects a code of a specific frequency included in an audio signal to function,
For each code, a specific frequency band including the specific frequency is preset,
Frequency analysis means for detecting the power of the frequency component in each specific frequency band for each code from the audio signal;
In each specific frequency band for each code, a maximum determination that determines whether or not the power in the specific frequency band is “maximum” relative to the power in other frequency bands around both sides of the specific frequency band Means,
Among one or more specific frequency bands determined to be maximal, as specific frequency detection means for detecting a specific frequency with the maximum power, and code output means for outputting a code associated with the detected specific frequency Make the computer work,
The specific frequency band and other frequency bands around both sides of the specific frequency are frequency resolutions of Fourier transform based on the sampling frequency.
The computer is made to function as described above .

According to the present invention, in a tone signal detection method using a device in which a specific frequency is pre-assigned for each code and a code of a specific frequency included in the audio signal is detected.
For each code, a specific frequency band including the specific frequency is preset,
A first step of detecting the power of the frequency component in each specific frequency band for each code from the audio signal;
A second determination is made as to whether or not the power in the specific frequency band in each specific frequency band for each code is “maximum” with respect to the power in other frequency bands around both sides of the specific frequency band. And the steps
A third step of detecting a specific frequency at which power is maximum in one or more specific frequency bands determined to be maximal;
A fourth step of outputting a code associated with the detected specific frequency,
The specific frequency band and the other frequency bands around both sides of the specific frequency have a frequency resolution of Fourier transform based on a sampling frequency .

  According to the apparatus, program, and method of the present invention, even when high power is detected at a frequency component other than the transmitted DTMF signal due to the influence of noise mixed in the audio signal, the DTMF signal is detected as much as possible. can do.

It is a functional block diagram of the DTMF signal detector in a prior art. It is a graph showing the electric power with respect to the frequency component of the DTMF signal in a prior art. It is a functional block diagram of the DTMF signal detection apparatus in this invention. It is explanatory drawing showing the 1st determination of the maximum determination part in this invention. It is explanatory drawing showing the 2nd determination of the maximum determination part in this invention. It is explanatory drawing showing the 1st specific frequency detection method. It is explanatory drawing showing the 2nd specific frequency detection method. It is explanatory drawing showing the 3rd specific frequency detection method. It is a sequence diagram of remote control using a DTMF signal. It is a function block diagram of the controlled side apparatus using this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a functional configuration diagram of the DTMF signal detection apparatus according to the present invention.

  According to FIG. 3, the DTMF signal detection apparatus 1 receives an audio signal and outputs a code having a specific frequency included in the audio signal. That is, a specific frequency is assigned in advance for each code. The DTMF signal detection apparatus 1 includes a frequency analysis unit 11, a local maximum determination unit 12 for each specific frequency, a specific frequency detection unit 13, and a code output unit 14. These functional components may be realized by executing a program that causes a computer mounted on the apparatus to function. The processing flow of these functional configurations can also be understood as a DTMF signal detection method.

  In the following description, the DTMF signal detection device will be described. However, the present invention is not limited to application to a “DTMF signal”. That is, unlike a DTMF signal, a plurality of different specific frequencies may not be combined for each code, but one specific frequency may be associated with each code. “Specific frequency” means a frequency assigned to the code.

[Frequency analysis unit 11]
The frequency analysis unit 11 detects the power of the frequency component in each specific frequency band for each code from the audio signal. Here, the “specific frequency band” is a frequency band including the specific frequency for each code, and is set in advance. For example, when an audio signal having a sampling frequency of 8 kHz is analyzed using a 512-point fast Fourier transform, the frequency resolution is 15.625 Hz. That is, 15.625 Hz including the specific frequency is the specific frequency band. Further, in addition to the specific frequency band, the power of the frequency band before and after that used by the local maximum determination unit 12 is detected. That is, the frequency analysis unit 11 has eight types of specific frequencies including each specific frequency of the low group tone (697 Hz, 770 Hz, 852 Hz, 941 Hz) and each specific frequency of the high group tone (1209 Hz, 1336 Hz, 1477 Hz, 1633 Hz). The power value of the band and the power values of the frequency bands around both sides of each specific frequency band are output to each local maximum determination unit 12 for each specific frequency. As a frequency analysis method, a necessary number of band filters and other frequency analysis techniques may be used in addition to calculating a power spectrum by Fourier transform.

[Maximum determination unit 12]
For example, in the case of a DTMF signal, eight local maximum determination units 12 are provided. The maximum determination unit 12 determines whether or not the power in the specific frequency band is “maximum” with respect to the power in other frequency bands around both sides of the specific frequency band. Then, the determination result (maximum / non-maximum) and the power value when determined to be the maximum are output to the specific frequency detection unit 13. As a result, even if the audio signal includes noise, the specific frequency determined to be non-maximal is not detected, and erroneous detection of specific frequencies other than the DTMF signal can be reduced as much as possible.

  Further, in the case of a DTMF signal, the maximum determination unit 12 may determine whether or not each of the high group tone and the low group tone is “maximum”.

The maximum determination unit 12 can make various maximum determinations, and two specific determination methods will be described below.
<First maximum determination method>
FIG. 4 is an explanatory diagram illustrating the first determination of the maximum determination unit in the present invention.

The specific frequency band centered on the specific frequency has a frequency resolution of 15.625 Hz when, for example, a 512-point fast Fourier transform is used for an audio signal with a sampling frequency of 8 kHz. That is, the power P _{f-15.625 in the} frequency band lower by _15.625 Hz and the power P _{f + 15.625 in the} frequency band higher by _15.625 Hz are compared with the center of the frequency band including the specific frequency f. Determine. Of course, the comparison target is not limited to the frequency band separated by one frequency resolution, but may compare the power of several frequency bands separated from each other.

The maximum determination unit 12 determines whether or not the power in the specific frequency band is “maximum” with respect to the power in other frequency bands around both sides of the specific frequency band. According to FIG. 4, power values in at least three frequency bands are used as follows.
Band power including the specific frequency f at the center: P _f
Power in a band including the first frequency that is lower than the specific frequency f by a predetermined value Δ: P _f−Δ
Power in a band including a second frequency that is higher than the specific frequency f by a predetermined value Δ: P _{f + Δ}
Here, in order to determine “maximum”, it is necessary that the following relationship holds.
P _f > P _f−Δ and P _f > P _{f + Δ}
The “specific frequency band” and the “other frequency band” may be, for example, one spectrum analysis band (or several).

<Second maximum determination method>
FIG. 5 is an explanatory diagram illustrating the second determination of the maximum determination unit in the present invention.

The local maximum determination unit 12 determines that the local maximum is obtained when the amount of change with respect to P _f−Δ and P _{f + Δ} is greater than or equal to a predetermined threshold with the power P _f in the band including the specific frequency f as the center. Here, the amount of change is calculated from the difference between P _f−Δ and P _{f + Δ with} respect to the power P _f in the specific frequency band.
First threshold: θ _f-Δ
Second threshold: θ _{f + Δ}
Here, in order to determine “maximum”, it is necessary that the following relationship holds.
(P _f −P _f−Δ )> θ _f−Δ and (P _f −P _{f + Δ} )> θ _{f + Δ}
Thus, if the change in the power spectrum of the specific frequency is not steep, it is determined that the signal is not a DTMF signal. That is, when the power spectrum changes slowly, it is determined that there is a high possibility of other noise.

[Specific frequency detector 13]
The specific frequency detection unit 13 detects a specific frequency at which power is maximum among one or more specific frequencies determined to be maximum. For example, in the case of a DTMF signal, a specific frequency that maximizes power is selected from the high group tone and the low group tone. That is, two specific frequencies are detected. The specific frequency detection unit 13 outputs “no specific frequency” to the code output unit 14 when there is no specific frequency determined to be maximum.

  In addition, the specific frequency detection unit 13 may detect only the specific frequency at which the power is maximum when the power is equal to or greater than a predetermined threshold. As a result, it is possible to avoid selecting a specific frequency that maximizes the power due to the influence of noise as much as possible even though the DTMF signal is not transmitted. This is particularly effective when the power level of the DTMF signal is known.

The specific frequency detection unit 13 can detect various specific frequencies, and three specific detection methods will be described below.
<First specific frequency detection method>
The specific frequency detection unit 13 executes the following two steps.
(S11) For each of the high group tone and the low group tone, a specific frequency with the maximum power is selected from one or more specific frequency bands determined to be maximum.
(S12) The specific frequency is detected only when the power value of each specific frequency band selected for each of the high group tone and the low group tone is equal to or greater than the predetermined threshold values θ _H and θ _L. For example, the following relationship is established.
_{max x∈XL P (x)> θ} L X L = {x∈T L | power frequency band x is maximum}
_{max x∈XH P (x)> θ} H X H = {x∈T H | power frequency band x is maximum}
T _L = {697Hz, 770Hz, 852Hz, 941Hz}
T _H = {1209Hz, 1336Hz, 1477Hz, 1633Hz}
max: Maximum value among multiple elements
θ _L : Power threshold for low group tone
θ _H : power threshold for high group tone

  FIG. 6 is an explanatory diagram illustrating a first specific frequency detection method.

According to FIG. 6A, a specific frequency of power equal to or higher than the predetermined threshold values θ _H and θ _L is detected for each of the high group tone and the low group tone. As a result, one code is detected as a result. On the other hand, according to FIG. 6B, for the low group tone, the specific frequency of power equal to or higher than the predetermined threshold θ _L is not detected. As a result, no code is detected.

<Second specific frequency detection method>
The specific frequency detection unit 13 executes the following two steps.
(S21) For each of the high group tone and the low group tone, a specific frequency with the maximum power is selected from one or more specific frequency bands determined to be maximum.
(S22) The power value of each specific frequency band selected for each of the high group tone and the low group tone and the average power value of the other specific frequency band not selected by combining the high group tone and the low group tone. The specific frequency is detected only when the difference is equal to or greater than the predetermined threshold values θ _H and θ _L.
P (F _maxL ) −P _ave > θ _L
F _maxL = argmax _x∈XL P (x)
X _L = {x∈T _L | power frequency band x is maximum}
P (F _maxH ) −P _ave > θ _H
F _maxH = argmax _x∈XH P (x)
X _H = {x∈T _H | power in frequency band x is maximal}
P _ave = Σ _x∈Fnotmax P (x) / 6
F _notmax = {x∈T _L ∪T _H | x ≠ F _maxL and x ≠ F _maxH }
T _L = {697Hz, 770Hz, 852Hz, 941Hz}
T _H = {1209Hz, 1336Hz, 1477Hz, 1633Hz}
θ _L : Power threshold for low group tone
θ _H : power threshold value in high group tone Here, P (x) is the power of frequency band x, and “P _ave = Σ _x∈Fnotmax P (x) / 6” is the case of DTMF signal, It means the average value P _ave of power in the other six specific frequency bands excluding the specific frequency of the maximum power value in the high group tone and the specific frequency of the maximum power value in the low group tone.

  FIG. 7 is an explanatory diagram illustrating a second specific frequency detection method.

According to FIG. 7A, the power value of each specific frequency band selected for each of the high group tone and the low group tone and the other specific frequency bands not selected by combining the high group tone and the low group tone. The difference in comparison with the average power value is equal to or greater than the predetermined threshold values θ _H and θ _L. As a result, one code is detected as a result.
On the other hand, according to FIG. 7B, the power value of the specific frequency selected from the low group tone and the average power value of the other specific frequency band not selected by combining the high group tone and the low group tone. Is smaller than the predetermined threshold value θ _L. Therefore, a specific frequency is not detected for the low group tone, and as a result, no code is detected.

<Third specific frequency detection method>
The specific frequency detection unit 13 executes the following two steps.
(S31) For each of the high group tone and the low group tone, a specific frequency with the maximum power is selected from one or more specific frequency bands determined to be maximal.
(S32) The power value of the specific frequency band selected for the high group tone is compared with the average power value of the other specific frequency band not selected for the high group tone, and the difference is equal to or greater than the predetermined threshold θ _H in matching, the power value of a specific frequency band selected for low group tones, compares the average power value of the other of the specific frequency band which is not selected for low group tones, the difference is greater than a predetermined threshold value theta _L Only in certain cases, the specific frequency is detected.
P (F _maxL ) −P _aveL > θ _L
F _maxL = argmax _x∈XL P (x)
x _L = {x∈T _L | maximum power in frequency band x}
P _aveL = Σ _x∈FnotmaxL P (x) / 3
_{F notmaxL = {x∈T L | x} ≠ F maxL}
P (F _maxH ) −P _aveH > θ _H
F _maxH = argmax _x∈XH P (x)
x _H = {x∈T _H | maximum power in frequency band x}
P _aveH = Σ _x∈FnotmaxH P (x) / 3
F _notmaxH = {x∈T _H | x ≠ F _maxH }
T _L = {697Hz, 770Hz, 852Hz, 941Hz}
T _H = {1209Hz, 1336Hz, 1477Hz, 1633Hz}
θ _L : power threshold value for low group tone θ _H : power threshold value for high group tone Note that “P _aveL = _{Σx∈FnotmaxL} P (x) / 3” is a low group tone in the case of a DTMF signal. The mean value P _aveL of the power of the other three specific frequency bands excluding the specific frequency band of the maximum power value. _PaveH is the same for the high group tone.

  FIG. 8 is an explanatory diagram illustrating a third specific frequency detection method.

According to FIG. 8A, the difference between the power value of the specific frequency band selected for the high group tone and the average power value of the other specific frequency band not selected for the high group tone is a predetermined threshold value. θ _H or more. Further, the difference between the power value of the specific frequency band selected for the low group tone and the average power value of the other specific frequency band not selected for the low group tone is equal to or greater than the predetermined threshold θ _L. As a result, one code is detected as a result.
On the other hand, according to FIG. 8B, the difference between the power value of the specific frequency band selected for the high group tone and the average power value of the other specific frequency band not selected for the high group tone. Is greater than or equal to a predetermined threshold θ _H. However, the difference between the power value of the specific frequency band selected for the low group tone and the average power value of the other specific frequency bands not selected for the low group tone is smaller than the predetermined threshold θ _L. Therefore, a specific frequency is not detected for the low group tone, and as a result, no code is detected.

[Code output unit 14]
For each code, a specific frequency band centered on each specific frequency is preset for each of the high group tone and the low group tone. Here, the code output unit 14 outputs a code associated with the detected specific frequency. In the case of a DTMF signal, the code output unit 14 outputs a code associated with a combination of a specific frequency detected with a high group tone and a specific frequency detected with a low group tone.

  FIG. 9 is a sequence diagram of remote operation using a DTMF signal.

  As a specific example, a case is assumed where the user controls the controlled terminal 1c via a telephone line. According to FIG. 9, the control code is converted into a DTMF signal, thereby enabling remote operation via a telephone line (see, for example, Patent Document 5). The communication terminal that has received the DTMF signal controls execution of the application for remote operation based on the control code extracted from the DTMF signal.

  The voice call may be via a telephone line (including a mobile phone line) or a packet line. In recent years, a terminal in a mobile phone or a smartphone is equipped with a plurality of communication interfaces and can be used properly according to usage. In the case of a telephone line, voice signals are transmitted / received using an analog signal band. In the case of a packet line, packets are transmitted / received using a digital signal band, but voice communication is performed by using VoIP (Voice over Internet Protocol). Is also possible.

(S1) The control-side telephone terminal 1a converts a control code request (for example, “201”) input by the user or mechanically into a DTMF audio signal. In the case of a DTMF signal, one code is assigned for each cycle time composed of a signal transmission time and a pause time. When the control code request is “201”, three codes (signal transmission time + pause time) are transmitted.
Signal transmission time: 50 ms or more Pause time: 80 ms or more Period: 120 ms or more (S2) Then, the control side telephone terminal 1a transmits the DTMF signal to the telephone terminal 1b via a voice call. The telephone terminal 1b utters the received DTMF signal from a speaker, and the controlled device 1c receives the DTMF signal through a microphone.
(S3) The controlled device 1c determines the code of the DTMF signal at regular intervals (for example, 10 ms). A plurality of codes output between the signal transmission time and the pause time are combined to determine and output one control code (see, for example, Patent Documents 6 and 7).
(S4) The controlled device 1c executes a process based on the control code.
Thereafter, the sequence of S1 to S4 is repeatedly executed sequentially for the control code.

  FIG. 10 is a functional configuration diagram of a controlled device using the present invention.

  According to FIG. 10, the terminal 1b is, for example, a mobile phone or a smartphone that can be moved wirelessly. The telephone line is, for example, a mobile phone network or a fixed telephone network, and the packet line is, for example, the Internet connected via an access network. The terminal 1b is a general telephone terminal that receives a voice signal with a counterpart terminal, and allows users to talk with each other by voice.

  The terminal 1b in FIG. 10 includes a telephone line interface 1b1, a packet line interface 1b4, a speaker 1b3, and a microphone 1b7 as hardware. The terminal 1b includes a VoIP unit 1b5, an audio signal receiving unit 1b2, and an audio signal transmitting unit 1b6 in terms of software. The VoIP unit 1b5 encodes / compresses the voice signal to convert it into a packet in real time, and decodes / decompresses the packet to convert it into a voice signal. The audio signal receiving unit 1b2 receives the audio signal from the telephone line interface 1b1 or the VoIP unit 1b5 and outputs the audio signal to the speaker 1b3. That is, in the telephone terminal 1b, the speaker 1b3 utters the voice signal received by the voice signal receiving unit 1b2.

  The controlled device 1c has only a microphone 1c7 and a remote controlled application 1c8. The functional configuration of the controlled device 1c has only the basic features of the present invention.

  According to the controlled device 1c, the voice signal uttered from the telephone terminal 1b is received by the microphone 1c7 of the controlled device 1c together with noise. The controlled device 1c detects the code of the DTMF signal included in the audio signal by the DTMF signal detector 1 of the remote control application 1c8. That is, the control side telephone terminal 1a can control the controlled side apparatus 1c by relaying the telephone terminal 1b using the DTMF signal. The controlled device 1c may be a home appliance, a sensor device, a communication access point, or the like.

  The DTMF signal detector 1 extracts a DTMF signal from the audio signal. The DTMF signal detection unit 1 detects alphanumeric characters corresponding to the frequency and outputs the alphanumeric characters to the control code execution unit. The control code execution unit executes control corresponding to the detected code. As a result, the controlled device 1c can accept remote control from the control-side telephone terminal 1a using the voice signal via the telephone terminal 1b.

  As described above in detail, according to the apparatus, program, and method of the present invention, it is possible to detect a specific frequency corresponding to a code as much as possible even for an audio signal including noise. In particular, even when high power is detected with frequency components other than the transmitted DTMF signal due to the influence of noise mixed in the audio signal, the DTMF signal can be detected as much as possible.

  According to the technique described in Patent Document 1, the apparatus utters a DTMF signal received via a telephone line as it is from a speaker and receives the sound by a microphone. Therefore, the air between the speaker and the microphone is affected by noise. The problem is that the DTMF signal is disturbed by noise and cannot be converted into an appropriate control code. By applying the DTMF signal detection device of the present invention, even if noise is included in the DTMF signal transmitted from the operator, it is detected as much as possible, and the remote control is executed.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

DESCRIPTION OF SYMBOLS 1 DTMF signal detector, DTMF signal detection part 11 Frequency analysis part 12 Maximum determination part 13 Specific frequency detection part 14 Code output part 1a Control side telephone terminal 1b Controlled side telephone terminal 1c Controlled side apparatus 1b1 Telephone line interface 1b2 Voice signal Reception unit 1b3 Speaker 1b4 Packet line interface 1b5 VoIP unit 1b6 Audio signal transmission unit 1c7 Microphone 1c8 Remote controlled application (control code execution unit)

Claims (9)

In the device for detecting a specific frequency code included in the audio signal, a specific frequency is assigned in advance for each code.
For each code, a specific frequency band including the specific frequency is preset,
Frequency analysis means for detecting power of frequency components in each specific frequency band for each code from the audio signal;
In each specific frequency band for each code, a maximum determination that determines whether or not the power in the specific frequency band is “maximum” relative to the power in other frequency bands around both sides of the specific frequency band Means,
Among one or more specific frequency bands determined to be maximal, specific frequency detecting means for detecting a specific frequency at which power is maximum, and code output means for outputting a code associated with the detected specific frequency And
The apparatus according to claim 1, wherein the specific frequency band and the other frequency bands around both sides of the specific frequency have a frequency resolution of Fourier transform based on a sampling frequency .   The apparatus according to claim 1, wherein the specific frequency detecting unit detects the specific frequency at which the power is maximum only when the power is equal to or greater than a predetermined threshold. A plurality of different specific frequencies are combined for each code,
The specific frequency detecting means detects a plurality of specific frequencies at which power is maximized,
The apparatus according to claim 1, wherein the code output unit outputs a code associated with a combination of a plurality of detected specific frequencies. The specific frequency is DTMF (Dual-Tone Multi-Frequency),
For each code, a specific frequency band centered on each specific frequency is set in advance for each of the high group tone and the low group tone,
For each of the high-group tone and the low-group tone, the local maximum determination means converts the power in the specific frequency band into the power in other frequency bands around both sides of the specific frequency band. On the other hand, determine whether it will be "maximum"
The specific frequency detection means detects a specific frequency at which power is maximum in one or more specific frequency bands determined to be maximal for each of the high group tone and the low group tone,
4. The apparatus according to claim 3, wherein the code output means outputs a code associated with a specific frequency detected with a high group tone and a specific frequency detected with a low group tone. The specific frequency detecting means includes
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from the one or more specific frequency bands determined to be maximum,
The apparatus according to claim 4, wherein the specific frequency is detected only when the power value of each specific frequency band selected for each of the high group tone and the low group tone is equal to or greater than a predetermined threshold value. The specific frequency detecting means includes
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from the one or more specific frequency bands determined to be maximum,
Compare the power value of each specific frequency band selected for each of the high group tone and the low group tone with the average power value of the other specific frequency bands not selected by combining the high group tone and the low group tone, The apparatus according to claim 4, wherein the specific frequency is detected only when the difference is equal to or greater than a predetermined threshold. The specific frequency detecting means includes
For each of the high group tone and the low group tone, the specific frequency that maximizes the power is selected from the one or more specific frequency bands determined to be maximum,
The power value of the specific frequency band selected for the high group tone is compared with the average power value of the other specific frequency band not selected for the high group tone, and the difference is equal to or greater than a predetermined threshold value,
Only when the power value of the specific frequency band selected for the low group tone is compared with the average power value of the other specific frequency bands not selected for the low group tone, and the difference is equal to or larger than a predetermined threshold value, The apparatus according to claim 4, wherein the specific frequency is detected. A specific frequency is assigned in advance for each code, and in a program for causing a computer mounted on a device that detects a code of a specific frequency included in an audio signal to function,
For each code, a specific frequency band including the specific frequency is preset,
Frequency analysis means for detecting power of frequency components in each specific frequency band for each code from the audio signal;
In each specific frequency band for each code, a maximum determination that determines whether or not the power in the specific frequency band is “maximum” relative to the power in other frequency bands around both sides of the specific frequency band Means,
Among one or more specific frequency bands determined to be maximal, specific frequency detecting means for detecting a specific frequency at which power is maximum, and code output means for outputting a code associated with the detected specific frequency cause the computer to function as,
The specific frequency band and other frequency bands around both sides of the specific frequency are frequency resolutions of Fourier transform based on the sampling frequency.
A program characterized by causing a computer to function . In a tone signal detection method using a device in which a specific frequency is assigned in advance for each code and a code of a specific frequency included in the audio signal is detected.
For each code, a specific frequency band including the specific frequency is preset,
A first step of detecting frequency component power in each specific frequency band for each code from the audio signal;
A second determination is made as to whether or not the power in the specific frequency band in each specific frequency band for each code is “maximum” with respect to the power in other frequency bands around both sides of the specific frequency band. And the steps
A third step of detecting a specific frequency at which power is maximum in one or more of the specific frequency bands determined to be maximum;
A fourth step of outputting a code associated with the detected specific frequency,
The tone signal detection method , wherein the specific frequency band and other frequency bands around both sides of the specific frequency have a frequency resolution of Fourier transform based on a sampling frequency .

Images