JP6163785B2 - Voice band extending apparatus and program - Google Patents

Description

  The present invention relates to a voice band extending apparatus and program, and can be applied to, for example, telephone equipment (including softphones).

  The frequency band of an audio signal that can be transmitted by a legacy telephone device is about 300 Hz to 3.4 kHz. Since the voice of such a narrowband voice signal that is band-limited to the telephone band has a higher quality than the original voice, there is a problem that it becomes difficult to hear words.

  In order to solve this problem, a band expansion technology has been developed to improve the clarity of voice by adding an extension signal of 3.4 kHz or more and expanding it to a wideband audio signal. The sound quality of the output audio signal is improved.

  The approach that the patent applicant has focused on is to generate an extended signal by processing the narrowband audio signal in the time domain, and synthesize the pseudoband audio signal by synthesizing the narrowband audio signal and the generated extended signal. It is an approach to generate. Most of the time domain processing is nonlinear processing. There are also many methods that use appropriate noise as part or all of the extended signal. Such an approach does not require a codebook to perform processing in the time domain, and thus has an advantage that bandwidth expansion can be realized with a small amount of calculation and a small amount of resources.

  FIG. 6 shows the most basic configuration in such an approach, and the configuration of FIG. 6 will be briefly described below.

  The voice band extending apparatus 100 having the configuration of FIG. 6 includes a sampling conversion unit 101, a band pass filtering unit (BPF) 102, a full wave rectification unit 103, a high pass filtering unit (HPF) 104, a frequency analysis unit 105, and an expansion gain calculation unit. 106, a multiplication unit 107 and an addition unit 108.

  The sampling converter 101 up-samples the narrowband audio signal S with a sampling frequency of 8 kHz into a signal with a sampling frequency of 16 kHz. The upsampled narrowband audio signal XL is supplied to the bandpass filtering unit 102 and the adding unit 108. For example, the band 2 kHz to 4 kHz of the up-sampled narrowband audio signal XL is filtered by the band pass filtering 102, and the filtered signal XB is full-wave rectified by the full-wave rectification unit 103, for example, to a band of 0 Hz to 8 kHz. The high-pass filtering 104 filters out a component of, for example, 4 kHz or more of the full-wave rectified signal and generates an extended signal EH. The frequency analysis unit 105 frequency-analyzes the narrowband speech signal S to calculate a spectrum parameter SF related to at least one of the amplitude envelope of the frequency spectrum and the slope of the frequency spectrum. In the extension gain calculation unit 106, the spectrum parameter SF The expansion gain EG is calculated based on the above, and the obtained expansion gain EG is given to the multiplier 107 (the method described in Non-Patent Document 1 can be applied as a frequency analysis and expansion gain calculation method). The multiplier 107 multiplies the generated extension signal EH by the calculated extension gain EG to adjust the amplitude of the extension signal, and the adder 108 adjusts the amplitude of the upsampled narrowband audio signal XL. The expanded signal XH is combined (added) to generate a pseudo wideband audio signal X.

Naofumi Aoki, “A Band Extension Technology for Narrow-Band Telephony Speech Base on Full Wave Rectification”, IEICE Trans. Commun. , Vol. E93-B (3), pp. 729-731, 2010.

  However, in the conventional voice band extension device, the high frequency range of the unvoiced sound cannot be sufficiently expanded, the intelligibility and intelligibility of the voice cannot be improved, and the generated pseudo wideband voice becomes a voice that is audibly muffled. was there.

  If you try to avoid this and try to extend the high range of the unvoiced sound forcibly, the voiced sound will be expanded excessively, and the generated pseudo-wideband speech will become a sound that is audibly superimposed with noise. there were.

  The present invention is intended to solve the above-described conventional problems, and extends outside the limited band of narrowband voice with a limited frequency band with a small amount of computation, and the expanded voice is practically sufficient. The objective is to have a high level of speech quality and intelligibility.

According to a first aspect of the present invention, there is provided an audio band extending apparatus for extending a narrow band audio signal having a limited frequency band so as to include an extended band signal component outside the limited band. Frequency analysis means for analyzing and obtaining spectral parameters; (2) power information obtaining means for obtaining power information relating to the narrowband audio signal; and (3) the magnitude of the extension component in the extension band signal based on the spectrum parameters. And an expansion gain forming means for dynamically controlling an acquisition method of the expansion gain according to the power information, and (4) the expansion gain forming means The maximum value of the expansion gain is limited according to the magnitude of the power information .
According to a second aspect of the present invention, there is provided an audio band extending apparatus for extending a narrow band audio signal having a limited frequency band so as to include an extended band signal component outside the limited band. Frequency analysis means for analyzing and obtaining spectral parameters; (2) power information obtaining means for obtaining power information relating to the narrowband audio signal; and (3) the magnitude of the extension component in the extension band signal based on the spectrum parameters. And an expansion gain forming means for dynamically controlling an acquisition method of the expansion gain according to the power information, and (4) the expansion gain forming means According to the power information, the ease of increasing the value of the expansion gain in the expansion gain calculation method is controlled.
According to a third aspect of the present invention, there is provided an audio band extending apparatus for extending a narrow band audio signal having a limited frequency band so as to include an extended band signal component outside the limited band. Frequency analysis means for analyzing and obtaining spectral parameters; (2) power information obtaining means for obtaining power information relating to the narrowband audio signal; and (3) the magnitude of the extension component in the extension band signal based on the spectrum parameters. And an expansion gain forming means for dynamically controlling an acquisition method of the expansion gain according to the power information, and (4) the expansion gain forming means According to the power information, a nonlinear equation parameter (an exponent of a square term) of the expansion gain calculation method is controlled.
According to a fourth aspect of the present invention, there is provided an audio band extending apparatus for extending a narrow band audio signal having a limited frequency band so as to include an extended band signal component outside the limited band. Frequency analysis means for analyzing and obtaining spectral parameters; (2) power information obtaining means for obtaining power information relating to the narrowband audio signal; and (3) the magnitude of the extension component in the extension band signal based on the spectrum parameters. And an expansion gain forming means for dynamically controlling an acquisition method of the expansion gain according to the power information, and (4) the expansion gain forming means As a method for calculating the expansion gain, it is possible to correspond to equations of a linear function and a quadratic function, and according to the magnitude of the power information, the calculation method of the expansion gain to be applied is one. Voice band expansion unit and selects any of the functions and secondary functions.
According to a fifth aspect of the present invention, there is provided an audio band extending apparatus for extending a narrow band audio signal having a limited frequency band so as to include an extended band signal component outside the limited band. A frequency analyzing means for analyzing and obtaining a spectral parameter including a narrow band low band power including a band lower than a predetermined frequency, a narrow band high band power including a band higher than the predetermined frequency, and a gradient index; (2) power information acquisition means for obtaining power information related to the narrowband audio signal, and (3) an expansion gain for adjusting the magnitude of the extension component in the extension band signal based on the spectrum parameter, Depending on the magnitude of the power information, either the value obtained by dividing the narrow band high band power by the narrow band low band power or the gradient index Characterized in that it comprises a extension gain forming means or the obtained by selecting used.

According to a sixth aspect of the present invention, there is provided an audio band expansion program comprising: (1) frequency analysis means for obtaining a spectrum parameter by frequency analysis of the narrowband speech signal; (2) power information acquisition means for obtaining power information relating to the narrowband speech signal; and (3) based on the spectrum parameter. Obtaining an extension gain for adjusting the magnitude of the extension component in the extension band signal, and functioning as an extension gain forming means for dynamically controlling an acquisition method of the extension gain according to the power information. (4) The expansion gain forming means limits the maximum value of the expansion gain according to the magnitude of the power information .
According to a seventh aspect of the present invention, there is provided an audio band expansion program comprising: (1) frequency analysis means for obtaining a spectrum parameter by frequency analysis of the narrowband speech signal; (2) power information acquisition means for obtaining power information relating to the narrowband speech signal; and (3) based on the spectrum parameter. Obtaining an extension gain for adjusting the magnitude of the extension component in the extension band signal, and functioning as an extension gain forming means for dynamically controlling an acquisition method of the extension gain according to the power information. (4) The expansion gain forming means increases the value of the expansion gain in the expansion gain calculation method according to the magnitude of the power information. And controlling the no longer reliable.
According to an eighth aspect of the present invention, there is provided an audio band expansion program comprising: (1) frequency analysis means for obtaining a spectrum parameter by frequency analysis of the narrowband speech signal; (2) power information acquisition means for obtaining power information relating to the narrowband speech signal; and (3) based on the spectrum parameter. Obtaining an extension gain for adjusting the magnitude of the extension component in the extension band signal, and functioning as an extension gain forming means for dynamically controlling an acquisition method of the extension gain according to the power information. (4) The expansion gain forming means is a parameter (square term) of a nonlinear expression of the expansion gain calculation method according to the magnitude of the power information. And controlling the index).
According to a ninth aspect of the present invention, there is provided an audio band expansion program comprising: (1) frequency analysis means for obtaining a spectrum parameter by frequency analysis of the narrowband speech signal; (2) power information acquisition means for obtaining power information relating to the narrowband speech signal; and (3) based on the spectrum parameter. Obtaining an extension gain for adjusting the magnitude of the extension component in the extension band signal, and functioning as an extension gain forming means for dynamically controlling an acquisition method of the extension gain according to the power information. (4) The expansion gain forming means can correspond to a linear function and a quadratic function as a method of calculating the expansion gain, Depending on, and selects the one of the primary functions and secondary functions of the method of calculating the extended gain applied.
According to a tenth aspect of the present invention, there is provided a voice band expansion program comprising: (1) The narrowband audio signal is frequency-analyzed, and the narrowband low band power including a band lower than a predetermined frequency, the narrowband high band power including a band higher than the predetermined frequency, and a gradient index Frequency analysis means for obtaining a spectrum parameter including: (2) power information acquisition means for obtaining power information relating to the narrowband audio signal; and (3) a magnitude of an extension component in the extension band signal based on the spectrum parameter. The expansion gain for adjusting the value is obtained by dividing the high band power in the narrow band by the low band power in the narrow band according to the magnitude of the power information. Characterized in that to function as an extended gain forming means capable to select the use of either of the feature value of the gradient index.

  According to the present invention, the high frequency range of the unvoiced sound can be sufficiently expanded, and as a result, the intelligibility and intelligibility of the voice are improved, and a pseudo-wideband audio signal having an audibly clear extension is generated. It is possible to provide a voice band expansion device and a program that can

It is a scatter diagram of the low frequency component power of 0 Hz to 4 kHz and the high frequency component power of 4 kHz to 8 kHz of the wideband sound. It is a functional block diagram which shows the structure of the audio | voice band expansion method of 1st Embodiment. It is a functional block diagram which shows the structure of the audio | voice band expansion method of 2nd Embodiment. It is a functional block diagram which shows the structure of the audio | voice band expansion method of 3rd Embodiment. It is a functional block diagram which shows the structure of the audio | voice band expansion method of 4th Embodiment. It is a functional block diagram which shows the structure of the conventional basic audio | voice band expansion apparatus.

(A) Technical idea common to each embodiment First, the technical idea common to these embodiments will be described before describing the audio band expansion device of each embodiment.

  The audio band expansion device of each embodiment is intended to dynamically change the expansion gain that is multiplied by the generated expansion signal in accordance with the narrowband audio power before expansion.

  FIG. 1 shows a low frequency component of 0 Hz to 4 kHz (corresponding to a signal for which a narrow band audio power is calculated) and a high frequency component of 4 kHz to 8 kHz from a wideband audio signal with a sampling frequency of 16 kHz that is not limited to the telephone band. Are plotted by using appropriate LPF and HPF, and a scatter diagram is plotted with the horizontal axis representing the power of the low frequency component and the vertical axis representing the power of the high frequency component. As can be seen from FIG. 1, the power of the high frequency component increases only when the power of the low frequency component is small, and the power of the high frequency component cannot increase when the power of the low frequency component is large.

  Based on such facts, the voice band extending apparatus of each embodiment dynamically determines the extension gain so that the maximum value of the extension gain is limited, for example, depending on the magnitude of the narrow band voice power, The expansion gain is dynamically determined so that the ease of increasing the value of the expansion gain is adjusted (a specific method will be described later), the horizontal axis is the narrowband audio power, and the vertical axis is the expansion signal. When a scatter diagram with the power of is drawn, the characteristics close to those of FIG. 1 described above can be obtained.

(B) First Embodiment Next, a first embodiment of a voice band extending apparatus and program according to the present invention will be described with reference to the drawings.

(B-1) Configuration of the First Embodiment FIG. 1 is a block diagram showing a functional configuration of the voice band extending apparatus according to the first embodiment, which is the same as in FIG. , The corresponding symbols are attached. Each part of the voice band extending apparatus according to the first embodiment may be configured by hardware, or may be configured as a CPU and a program (voice band extending program) executed by the CPU (for example, The function of each block shown in FIG. 1 may be configured as a subroutine of a program). Functionally, it can be represented by FIG.

  In FIG. 1, a voice band extension device 200 according to the first embodiment is similar to the voice band extension device 100 shown in FIG. 6, and includes a sampling conversion unit 101, a band pass filtering unit (BPF) 102, and a full wave rectification unit 103. A high-pass filtering unit (HPF) 104, a frequency analysis unit 105, a multiplication unit 107, an addition unit 108, a power calculation unit 209, and an expansion gain calculation unit 210, which are unique to the voice band expansion device 200 of the first embodiment.

  The power calculation unit 209 calculates the power SP of the narrowband audio signal S and supplies it to the extension gain calculation unit 210.

  The expansion gain calculation unit 210 uses a predetermined variable expansion gain calculation method to convert the spectral parameter SF given from the frequency analysis unit 105 and the power SP of the narrowband audio signal S given from the power calculation unit 209. Based on this, the expansion gain EG is calculated, and the obtained expansion gain EG is given to the multiplication unit 107.

(A-2) Operation of the First Embodiment Next, the operation of the voice band extending method apparatus 200 of the first embodiment will be described.

  Here, the voice band extending apparatus 200 of the first embodiment includes a power calculation unit 209, and the expansion gain calculation unit 210 uses not only the output of the frequency analysis unit 105 but also the output of the power calculation unit 209. Since the point is different from the above-described voice band extending apparatus 100 shown in FIG. 6, the operation of the power calculating unit 209 and the extended gain calculating unit 210 will be described below after referring to the operation of the frequency analyzing unit 105.

  As described above, the frequency analysis unit 105 performs frequency analysis on the narrowband audio signal S and calculates a spectral parameter SF related to at least one of the amplitude envelope of the frequency spectrum and the slope of the frequency spectrum.

  Examples of such a calculation method include the method described in Non-Patent Document 1 and the method proposed by the same inventor in Japanese Patent Application No. 2012-258651.

In the former method, the gradient index GI expressed by the following equations (1) to (4) is the spectrum parameter SF. The gradient index GI is an index that represents the number of times and the magnitude of the change in the inclination direction of the signal waveform. In the equations (1) to (4), n is a time element number, and S (n) is a narrowband audio signal.

In the calculation method proposed in Japanese Patent Application No. 2012-258651, the modified gradient index MGI expressed by any of the following formulas (5) to (8) is the spectral parameter SF. The corrected gradient index MGI is a parameter that has a high correlation with the gradient index GI and has a smaller value jump than the gradient index GI. Further, a parameter MGI ′ (n) obtained by smoothing the modified gradient index MGI defined in the equations (9) and (10) proposed in Japanese Patent Application No. 2012-258651 is used as a spectral parameter SF. It may be applied. In the formula (9), b is a forgetting factor of 0 or more and less than 1.

  The power calculation unit 209 calculates the power SP of the narrowband audio signal S and supplies the obtained power SP of the narrowband audio signal S to the extension gain calculation unit 210. Here, any method can be used to calculate the power. For example, the moving average of the absolute value of the narrowband audio signal S or the moving average of the square value of the narrowband audio signal S can be used as the power SP of the narrowband audio signal S.

  Depending on the frequency analysis method applied by the frequency analysis unit 105, it may be necessary to calculate the power SP of the narrowband audio signal S in the frequency analysis unit 105. In such a case, the power calculation unit in the frequency analysis unit 105 and the power calculation unit 209 may be shared.

  The extension gain calculation unit 210 basically multiplies the spectrum parameter SF by a conversion coefficient to convert the spectrum parameter SF to the extension gain EG, and gives the obtained extension gain EG to the multiplication unit 107.

  In the case of the first embodiment, the conversion coefficient is not fixed, but dynamically changes according to the narrowband audio power SP. The relationship between the narrowband audio power SP and the conversion coefficient is determined in advance according to the relationship between the power of the low frequency component and the power of the high frequency component shown in FIG. The extension gain calculation unit 210 is a conversion table for converting the narrowband audio power SP into a conversion coefficient, or a conversion function (which may be a step function) for converting the narrowband audio power SP into a conversion coefficient. And obtaining a conversion coefficient corresponding to the input narrowband audio power SP, and then multiplying the spectral parameter SF by the conversion coefficient to obtain an expansion gain EG. Note that, after converting the narrowband audio power SP into a conversion coefficient, instead of multiplying the spectral parameter SF by the conversion coefficient to obtain the expansion gain EG, a conversion table or conversion equation to be applied according to the narrowband audio power SP is used. A method of directly converting the spectral parameter SF into the expansion gain EG may be applied by switching.

  As described above, the power of the high frequency component of the wideband audio signal having a sampling frequency of 16 kHz that is not limited to the telephone band is increased only when the power of the low frequency component is small, and the power of the low frequency component is large. Sometimes the power of the high frequency component cannot increase. Based on such facts, the above-described conversion table and conversion formula are formed in advance.

  For example, a method for converting the spectral parameter SF into the expansion gain EG may be determined so that the maximum value of the expansion gain EG is limited according to the magnitude of the narrowband audio power SP. A method of converting the spectral parameter SF into the expansion gain EG may be determined so that the ease of increasing the value is adjusted.

  Here, when the spectral parameter SF is scalar and the calculation method of the expansion gain is a method of obtaining the expansion gain EG by multiplying the spectral parameter SF by a positive conversion coefficient A as shown in the equation (11), For example, the maximum value SPmax that can be taken by the narrowband speech power SP is set in advance, the minimum value of the conversion coefficient A is Amin, the maximum value is Amax, and the conversion formula for converting the spectral parameter SF to the conversion coefficient A is ( You may make it apply the conversion formula of Formula 12).

EG = A · SF (11)
A = Amax− (Amax−Amin) · SP / SPmax (12)
According to the equations (11) and (12), when the narrowband sound power SP is large (corresponding to voiced sound), the expansion gain EG is relatively small by multiplying the spectrum parameter SF by a small conversion coefficient A. When the narrowband audio power SP is small (corresponding to an unvoiced sound), the expansion gain EG becomes a relatively large value by multiplying the spectrum parameter SF by a large conversion coefficient A. As a result, the horizontal axis is narrowband. When a scatter diagram (not shown) with the audio power SP and the vertical axis representing the power of the extension signal XH is drawn, the characteristics close to those of FIG. 1 described above can be obtained.

  Note that the method of dynamically determining the expansion gain EG according to the size of the narrowband audio power SP is not limited to the method using the equations (11) and (12). For example, the maximum value (upper limit value) EGmax of the expansion gain EG is dynamically calculated so that it is small when the narrowband audio power SP is large and large when the narrowband audio power SP is small, and is calculated by applying a fixed coefficient. When the value of the expansion gain EG exceeds the maximum value EGmax, the value of the expansion gain EG may be limited (replaced) to the maximum value EGmax. Further, for example, a method of dynamically limiting the maximum value of the expansion gain EG may be applied while controlling the conversion coefficient A (for example, applying equation (12)).

  The above-described equation (12) shows a case where there is a linear relationship between the narrowband audio power SP and the conversion coefficient A. However, a non-linear relational expression may be applied. In such a case, as a method of dynamically determining the expansion gain EG according to the magnitude of the narrowband audio power SP, a method of adjusting the nonlinearity may be used. For example, you may make it change the parameter (for example, exponent of a square term) of a nonlinear formula.

  In the above description, the conversion formula between the narrowband voice power SP and the conversion coefficient A (or the conversion formula between the narrowband voice power SP and the expansion gain EG) is described as an image that follows a continuous curve. However, one or more threshold values may be introduced into the narrowband audio power SP to be determined selectively (discretely (in other words, stepwise)).

  Further, unlike the dynamic determination methods exemplified so far, a plurality of extension gain calculation methods are prepared, and after selecting one of the extension gain calculation methods according to the narrowband audio power SP, the spectrum parameter is selected. SF may be converted into an expansion gain EG. For example, when one threshold value TSP for the narrowband voice power SP is set in advance and SP ≧ TSP, the extension gain EG is calculated by a linear function of the narrowband voice power SF, and when SP <TSP. May apply a method of calculating the expansion gain EG using a quadratic function of the expansion gain SF.

  Further, in the description of the dynamic determination method exemplified so far, it is described as if the spectral parameter SF is a scalar, but the spectral parameter SF is a vector or matrix having a plurality of parameters. Alternatively, the dynamic determination method may be a method of determining the type and number of parameters constituting the spectrum parameter SF.

  For example, the spectrum parameter SF has three parameters of band power (low band power in narrow band) SPL of 0 Hz to 2 kHz, band power (high band power in narrow band) SPH of 2 kHz to 4 kHz, and gradient index Gl. Assuming that one threshold value TSP for the narrowband voice power SP is set in advance, and when SP ≧ TSP, it is expanded based on a value obtained by dividing the narrowband highband power SPH by the narrowband lowband SPL. A method of calculating the gain EG and calculating the extension gain EG based on the gradient index GI when SP <TSP can be applied.

(B-2) Effect of First Embodiment According to the first embodiment, the relationship between the power of the low frequency component and the power of the high frequency component in the wideband audio signal that is not limited to the telephone band is extended. Since the extension gain EG multiplied by the generated extension signal EH is dynamically determined according to the narrowband voice power SP so that the pseudo-wideband voice signal can be realized, the high frequency range of the unvoiced sound is sufficient. The voice clarity and intelligibility is improved, and the voiced sound is not excessively expanded and no new noise is superimposed on it. be able to.

(C) Second Embodiment Next, a second embodiment of the voice band extending apparatus and program according to the present invention will be described with reference to the drawings.

(C-1) Configuration of Second Embodiment FIG. 3 is a block diagram showing the configuration of the voice band extension apparatus of the second embodiment. The same and corresponding parts in FIG. Is shown.

  In FIG. 3, the voice band extending apparatus 300 according to the second embodiment is similar to the voice band extending apparatus 200 according to the first embodiment, in the sampling conversion unit 101, the band pass filtering unit (BPF) 102, and the full wave rectifying unit. 103, a high-pass filtering unit (HPF) 104, a frequency analysis unit 105, a multiplication unit 107, an addition unit 108, a power calculation unit 209, an extended gain calculation unit 210, a long-term average unit 311 unique to the second embodiment, a power normalization And a conversion unit 312.

  The long-term average unit 311 calculates the long-term average value longSP of the narrowband voice power SP given from the power calculation unit 209, and the obtained long-term average value longSP of the narrowband voice power is given to the power normalization unit 312. is there.

  The power normalization unit 312 calculates the normalized power NSP of the narrowband speech by dividing the narrowband speech power SP given from the power computation unit 209 by the long-term average value longSP given from the long-term average unit 311. Then, the normalized power NSP of the obtained narrowband speech is given to the extension gain calculation unit 210.

  Note that, unlike the first embodiment, the extension gain calculation unit 210 of the second embodiment uses the extension gain EG multiplied by the generated extension signal EH as the normalized power NSP of narrowband speech. It is determined dynamically according to the response.

(C-2) Operation of Second Embodiment Next, the operation of the voice band extending apparatus 300 of the second embodiment will be described.

  Here, the voice band extending apparatus 300 of the second embodiment is that the power information of the narrow band voice signal given to the extension gain calculating unit 210 is replaced with the normalized power NSP from the simple power SP. It is changed from the voice band extending apparatus 200 of the embodiment. Therefore, hereinafter, the operation of the long-term average unit 311 and the power normalization unit 312 related to the formation of the normalized power NSP will be mainly described.

  The long-term average unit 311 calculates the long-term average value longSP of the power SP of the narrowband speech given from the power calculation unit 209. Any method can be used as a method of calculating the long-term average value longSP. For example, moving average or smoothing by a time constant filter as shown in the equation (13) can be applied. In equation (13), tau is a time constant that takes a value in the range of 0 <tau <1, and the operator “←” represents assignment from the right side to the left side. If the length of the long-term average is T seconds, the average value for T seconds is the long-term average value when moving average is applied, and the time required for tracking is T seconds when the time constant filter is applied. A value smoothed by the time constant tau is defined as a long-term average value. Note that, when the moving average is applied, it is necessary to secure a relatively large memory area. Therefore, it is preferable to use a time constant filter as compared with the case where the moving average is applied. The long-term average length T is preferably about 5 to 20 seconds.

longSP ← tau / longSP + (1-tau) / SP
... (13)
The power normalization unit 312 calculates the normalized power NSP of the narrowband speech by dividing the narrowband speech power SP by the long-term average value longSP. Since the normalization power NSP of the narrowband speech is normalized by the long-term average value of the power of the narrowband speech that is input, it becomes a large value for the voiced sound regardless of the volume of the speaker and the microphone sensitivity, For unvoiced sounds, the value is small. That is, by this normalization processing, for example, when the voice of the speaker is low, the extended gain EG of the voiced sound period becomes excessive, or when the voice of the speaker is high, the extended gain EG of the unvoiced sound period becomes excessively small. Can be avoided.

  In addition, in calculating the long-term average value longSP of the power of the narrowband speech, the long-term average length T is finite, so even if the speaker changes or the microphone sensitivity changes, the narrowband speech power The normalized power NSP can be returned to an appropriate value after T seconds.

(C-2) Effects of Second Embodiment According to the second embodiment, in addition to the same effects as those of the first embodiment, the following effects can be achieved.

  According to the second embodiment, since the power of the narrowband speech is normalized by the long-term average value and reflected in the expansion gain, the degree of expansion of voiced and unvoiced sounds depends on the speaker's voice volume and microphone sensitivity. Even if the speaker or microphone sensitivity changes, it can be adapted to a new environment after a certain period of time, resulting in a more auditory voice with improved speech clarity and intelligibility. It is possible to obtain a pseudo wideband audio signal having a clear elongation.

(D) Third Embodiment Next, a third embodiment of the voice band extending apparatus and program according to the present invention will be described with reference to the drawings.

  FIG. 4 is a block diagram showing the configuration of the voice band extending apparatus according to the third embodiment. The same or corresponding parts as those in FIG. 3 according to the second embodiment described above are assigned the same or corresponding reference numerals. Show.

  In FIG. 4, the voice band extending apparatus 400 of the third embodiment includes a voice section detecting unit 413 in addition to the configuration of the voice band expanding apparatus 300 of the second embodiment, and the long-term average unit 414 is a voice section detecting unit. The point that the detection signal VAD from 413 is used is different from the voice band expansion device 300 of the second embodiment.

  Based on the narrowband speech signal S, the speech segment detection unit 413 determines whether the narrowband speech signal S is a speech segment or a silent segment, and gives the obtained speech segment determination result VAD to the long-term average unit 414.

  Here, any known method can be applied to the method of detecting a speech section. For example, it is possible to apply a method of observing the power of the narrowband audio signal S and determining a voice interval if the power is equal to or greater than a predetermined threshold and a silence interval if the power is less than the predetermined threshold. In this case, the amount of calculation in the voice section detection unit 413 can be reduced by replacing the narrow band voice signal S with the input to the voice section detection unit 413 as the narrow band voice power SP.

  The long-term average unit 414 of the third embodiment receives the input of the speech segment determination result VAD, and when the narrowband speech signal S is a speech segment, the long-term average unit 414 is similar to the long-term average unit 311 of the second embodiment. The long-term average value longSP of the power of the narrowband speech is updated. On the other hand, if the narrowband speech signal S is in the silent period, the value of the long-term average value longSP of the power of the narrowband speech is not updated (the previous value is changed). Hold). In this way, the long-term average value longSP of the power of the narrowband speech that has been updated or the long-term average value longSP of the power of the narrowband speech that has not been updated (the previous value is retained) is the power normalization unit 312. And processed as described in the second embodiment.

  In the silent section, the narrow band voice power SP is small regardless of the speaker and microphone sensitivity. Therefore, in the third embodiment, the update of the long-term average value longSP of the power of the narrowband speech in the silent period is stopped to avoid the long-term average value longSP following the power of the silent period and becoming smaller. ing.

  According to the third embodiment, in addition to the same effects as those of the second embodiment, the following effects can be achieved.

  According to the third embodiment, since the update of the long-term average value of the power of the narrowband speech is stopped in the silent period, the long-term average value can be prevented from becoming unintentionally too small, and the degree of expansion is stable. Thus, a pseudo broadband audio signal can be obtained.

(E) Fourth Embodiment Next, a fourth embodiment of the voice band extending apparatus and program according to the present invention will be described with reference to the drawings.

  FIG. 5 is a block diagram showing the configuration of the voice band extending apparatus according to the fourth embodiment. The same or corresponding parts as those in FIG. 2 according to the first embodiment described above are assigned the same or corresponding reference numerals. Show.

  In FIG. 5, the voice band extending apparatus 500 according to the fourth embodiment is provided with a signal processing unit 513 in addition to the configuration of the voice band extending apparatus 200 according to the first embodiment. This is different from the voice band expansion device 200.

  The signal processing unit 515 performs predetermined signal processing on the input narrowband audio signal S to obtain a processed narrowband audio signal S ′, and provides it to the frequency analysis unit 105 and the power calculation unit 209.

  Here, the predetermined signal processing includes, for example, a wide variety of signal processing such as high-band emphasis filtering generally called pre-emphasis, noise suppression, and formant emphasis. The signal processing performed by the signal processing unit 515 may be one type, or two or more types of signal processing may be performed. Since the high-band emphasis filtering described above is a filter that cancels the radiation characteristic of the lips, the phoneme of narrow-band speech can be more accurately reflected in the spectrum parameter SF. Further, in a noise environment, it is possible to prevent the spectrum parameter SF from being disturbed by noise by performing noise suppression. Further, the phoneme may be further enhanced by combining noise suppression and high-frequency emphasis filtering.

  In FIG. 5, it is described that the processed narrowband audio signal S ′ obtained by the signal processing unit 515 is provided to the frequency analysis unit 105 and the power calculation unit 209, but the processed narrowband audio signal S ′ is illustrated. May be provided to either the frequency analysis unit 105 or the power calculation unit 209, or the sampling conversion unit 101 may be provided with the processed narrowband audio signal S ′ instead of the narrowband audio signal S. In addition, the signal processing unit 515 includes a plurality of signal processing units having different configurations, and obtains a processed narrowband audio signal that has been subjected to different signal processing, and includes a sampling conversion unit 101, a frequency analysis unit 105, and a power calculation unit It is also possible to adopt a configuration that is given only to the corresponding ones.

  According to the fourth embodiment, in addition to the same effects as those of the first embodiment, the following effects can be achieved.

  According to the fourth embodiment, after appropriate processing is performed on the narrowband audio signal, the subsequent expansion processing and analysis processing are executed, so that the reflection of phonology is enhanced or the influence of noise is reduced. As a result, it is possible to obtain a pseudo wideband audio signal with improved voice clarity and intelligibility.

(F) Other Embodiments In the description of each of the above embodiments, various modified embodiments have been referred to, but further modified embodiments can be exemplified.

  In the fourth embodiment, a signal processing unit is introduced with respect to the technical idea of the first embodiment. However, the fourth embodiment is different from the technical idea of the second or third embodiment. The signal processing unit described in the embodiment may be introduced.

  In each of the above-described embodiments, the extended signal generation method generates the full-wave rectified wave of the signal extracted from 2 kHz to 4 kHz by the BPF by limiting it to the extended band by the HPF. Is not limited to this method. For example, instead of full-wave rectification processing, half-wave rectification processing, power calculation such as square, tanh calculation, or the like may be applied. In addition, although nonlinear processing is described here, linear processing may be performed. The extraction band by BPF is not limited to 2 kHz to 4 kHz, and may not perform filtering by BPF. In each of the above embodiments, the audio signal is extended. However, the extended signal may be generated using a sound source signal obtained by linear prediction analysis or the like, and a noise generation source is included in the configuration. You may make it produce | generate an extended signal using the noise signal output from a noise generation source. Further, an extended signal may be generated by combining a plurality of signals statically or dynamically.

  In each of the above embodiments, the user may be able to manually control and select various parameters of the expansion gain calculation unit 210, the expansion gain calculation method, and the dynamic determination method. As a result, it is possible to realize an audio band expansion device that can obtain a pseudo wideband audio signal having a sound quality suited to the user's preference. Here, the options that can be selected by the user may be switched according to narrowband audio power information (the narrowband audio power itself or the normalized power of the narrowband audio). Among them, the conversion formula and parameters may be changed in accordance with the information on the narrowband audio power.

  Further, in each of the above embodiments, various parameters of the expansion gain calculation unit 210, the expansion gain calculation method, and the dynamic determination method can be automatically controlled based on the result of analyzing the narrowband audio signal S. May be. For example, the switching is performed according to the information of the speaker property such as the long-term average value of the spectrum envelope and the long-term average of the pitch frequency. In this way, it is possible to realize a voice band expansion device that automatically adapts to the usage environment. Here, in the process of the automatically controlled method, the conversion formula and parameters may be changed according to the information on the narrowband audio power.

  In the second embodiment, the third embodiment, or the fourth embodiment including the long-term average unit 311 or the long-term average unit 414, the user may be able to manually control the long-term average length T. . As a result, it is possible to realize a voice band expansion device that matches the user's preference with the follow-up speed to environmental changes.

  In the second embodiment, the third embodiment, or the fourth embodiment including the long-term average unit 311 or the long-term average unit 414, the long-term average length T is set to the narrowband audio signal S or the processed narrowband. It may be possible to automatically control based on the result of analyzing the audio signal S ′. For example, the switching may be performed according to the information on the amount of change in the speaker property and the frequency and length of the silent section. In this way, it is possible to realize a voice band expansion device that automatically adapts to the usage environment.

  In the fourth embodiment including the signal processing unit 515, the user may be able to manually control the contents and parameters of signal processing performed on the narrowband audio signal S. As a result, it is possible to realize an audio band expansion device that can obtain a pseudo wideband audio signal having a sound quality suited to the user's preference.

  Further, in the fourth embodiment including the signal processing unit 515, the contents and parameters of the signal processing applied to the narrowband audio signal S can be automatically controlled based on the analysis result of the narrowband audio signal S. May be. For example, the switching may be performed according to the information regarding the amount of change in the speaker property, the frequency and the length of the silent section. In this way, it is possible to realize a voice band expansion device that automatically adapts to the usage environment.

  The narrowband audio signal S input to the audio band extension device of each of the above embodiments may be transmitted from a facing communication device or read from a recording medium or the like. . In addition, the pseudo wideband audio signal X obtained by the audio band extending device of each of the above embodiments may be output as a sound from a speaker or the like, may be transmitted to another device, or may be recorded on a recording medium. good.

  DESCRIPTION OF SYMBOLS 200, 300, 400, 500 ... Voice band expansion apparatus, 101 ... Sampling conversion part, 102 ... Band pass filtering part (BPF), 103 ... Full wave rectification part, 104 ... High pass filtering part (HPF), 105 ... Frequency analysis part , 107 ... Multiplier, 108 ... Adder, 209 ... Power calculator, 210 ... Expansion gain calculator, 311, 414 ... Long-term average part, 312 ... Power normalizer, 413 ... Voice section detector, 515 ... Signal processing Department.

Claims (16)

In an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Gain forming means ,
The extension band forming device restricts the maximum value of the extension gain according to the magnitude of the power information . In an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Gain forming means,
The extension gain forming means, the according to the magnitude of the power information, the expanded gain the expanded gain controlling the increases and ease features and to Ruoto voice band extender to the values in the calculation method. In an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Gain forming means,
The extension gain forming means, according to the magnitude of the power information, the expanded gain nonlinear equation parameters characteristic and to Ruoto voice band extending apparatus to control the (squared term index) calculation method. In an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Gain forming means,
The expansion gain forming means can correspond to the expression of a linear function and a quadratic function as a method of calculating the expansion gain, and the expansion gain calculation method to be applied depends on the magnitude of the power information. features and to Ruoto voice band extender to select one of the functions. In an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A spectrum including the narrowband low band power including a band lower than a predetermined frequency, the narrow band high band power including a band higher than the predetermined frequency, and a gradient index by performing frequency analysis on the narrowband audio signal. Frequency analysis means for obtaining parameters;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectral parameter, the expansion gain for adjusting the magnitude of the expansion component in the expansion band signal is divided by the low band power in the narrow band according to the magnitude of the power information. Extended gain forming means obtained by selecting which of the feature values of the measured value and the gradient index to use
A voice band extending apparatus comprising: The power information acquisition means is
A power calculator for calculating the power of the narrowband audio signal;
A long-term average part for obtaining a long-term average value of the power of the narrowband audio signal;
A power normalization unit that obtains normalized power by dividing the power of the narrowband audio signal by the long-term average value of the power of the narrowband audio signal;
The voice band extending apparatus according to any one of claims 1 to 5 , wherein the normalized power is output as the power information. The power information acquisition unit further includes a voice section detection unit that determines whether the voice section is a silent section based on the narrowband voice signal, and the long-term average unit is when the voice section detection unit determines that the voice section is a voice section. 7. The voice band extending apparatus according to claim 6 , wherein the long-term average value is updated, and the long-term average value is held when the voice section detection unit determines that the voice section is a silent section. The apparatus further comprises signal processing means for obtaining a processed narrowband audio signal by performing predetermined signal processing on the narrowband audio signal, and the processed narrowband audio signal is input to the frequency analysis means and the power information acquisition means. The voice band extending device according to any one of claims 1 to 7 , wherein 9. The voice band extending apparatus according to claim 8 , wherein the signal processing means performs at least one kind of signal processing, and high-band emphasis filtering is included in the signal processing. 9. The voice band extending apparatus according to claim 8 , wherein the signal processing means performs at least one kind of signal processing, and noise suppression is included in the signal processing. 9. The voice band extending apparatus according to claim 8 , wherein the signal processing means performs at least one kind of signal processing, and formant emphasis is included in the signal processing. A computer mounted on an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Function as a gain forming means ,
The voice band extension program , wherein the extension gain forming means limits the maximum value of the extension gain according to the magnitude of the power information . A computer mounted on an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Function as a gain forming means,
The expansion gain forming means controls the ease of increasing the value of the expansion gain in the expansion gain calculation method according to the magnitude of the power information.
A voice band expansion program characterized by that. A computer mounted on an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Function as a gain forming means,
The expansion gain forming means controls a nonlinear parameter (an exponent of a square term) of the expansion gain calculation method according to the magnitude of the power information.
A voice band expansion program characterized by that. A computer mounted on an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A frequency analysis means for obtaining a spectral parameter by performing frequency analysis on the narrowband audio signal;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectrum parameter, an extension gain for adjusting the magnitude of the extension component in the extension band signal is obtained, and the extension gain acquisition method is dynamically controlled according to the power information. Function as a gain forming means,
The expansion gain forming means can correspond to the expression of a linear function and a quadratic function as a method of calculating the expansion gain, and the expansion gain calculation method to be applied depends on the magnitude of the power information. A voice band expansion program characterized by selecting one of the functions. A computer mounted on an audio band expansion device that expands a narrowband audio signal with a limited frequency band to include a signal component of an expansion band outside the limited band,
A spectrum including the narrowband low band power including a band lower than a predetermined frequency, the narrow band high band power including a band higher than the predetermined frequency, and a gradient index by performing frequency analysis on the narrowband audio signal. Frequency analysis means for obtaining parameters;
Power information acquisition means for obtaining power information related to the narrowband audio signal;
Based on the spectral parameter, the expansion gain for adjusting the magnitude of the expansion component in the expansion band signal is divided by the low band power in the narrow band according to the magnitude of the power information. Extended gain forming means obtained by selecting which of the feature values of the measured value and the gradient index to use
A voice band expansion program characterized by being made to function.

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