JP2014187474A - Audio signal processing device, acoustic device, method of controlling audio signal processing device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an audio signal processing device, an acoustic device, a method of controlling the audio signal processing device, and a program which implement stable power saving without auditorily influencing sound quality.SOLUTION: An audio signal processing section 12 provided in the acoustic device includes an amplitude control section 21 for reducing the amplitude of an audio signal, and a calculation management section 22 for calculating a ratio or difference between an integrated power consumption value before the amplitude control by the amplitude control section 21 and an integrated power consumption value after the amplitude control. The amplitude control section 21 performs the amplitude reduction control such that the calculation result of the calculation management section 22 is a fixed value.

Description

  The present invention relates to an audio signal processing device, an audio device, a control method for an audio signal processing device, and a program that perform audio signal processing for reducing power consumption of a speaker amplifier.

  In recent years, there is a high demand for using acoustic devices wirelessly, both domestically and internationally. However, on the other hand, there is a current situation that there is no satisfaction in the driving time of the battery. Thus, various techniques for reducing the power consumption of the speaker amplifier have been proposed in order to extend the battery driving time. For example, Patent Document 1 includes a speaker driving amplifier that amplifies an audio signal and a speaker that is driven by the output of the speaker driving amplifier, and cuts an audio signal outside the frequency band that the speaker can reproduce from the audio signal. A speaker system configured to input an audio signal limited to a reproducible frequency band of the speaker to a speaker driving amplifier has been proposed. In Patent Literature 1, the audio signal is band-limited in accordance with the reproducible frequency band of the speaker as described above, thereby suppressing unnecessary driving of the speaker and reducing power consumption.

JP 2009-111663 A

  However, in recent active speaker systems driven by a battery, audio signals are often band-limited in accordance with the reproducible frequency band of the speakers before being input to the amplifier. In such a case, the technique of Patent Document 1 cannot exhibit the effect. In addition to Patent Document 1, various techniques for reducing power consumption have been proposed, but there are problems such as sacrificing sound quality.

  In view of the above problems, the present invention provides an audio signal processing device, an audio device, a control method for an audio signal processing device, and a program capable of realizing stable power saving without affecting sound quality on hearing. The task is to do.

  The audio signal processing device of the present invention is configured to obtain a ratio or difference between an amplitude control unit that reduces the amplitude of an audio signal, a power consumption integrated value before amplitude control by the amplitude control unit, and a power consumption integrated value after amplitude control. And an amplitude control unit that feeds back a calculation result of the calculation unit and performs amplitude reduction control based on the fed back value.

  In the audio signal processing apparatus, the amplitude control unit performs amplitude reduction control so that a calculation result of the calculation unit becomes a constant value.

  The above audio signal processing apparatus further includes a reduction interval determination unit that determines a reduction interval for reducing the amplitude of the audio signal based on the maximum point of the amplitude envelope of the audio signal, and the amplitude control unit includes the reduction interval determination unit. Amplitude reduction control is performed on the determined reduction interval.

  In the audio signal processing apparatus, the amplitude control unit varies the amplitude attenuation coefficient of the reduction section according to the calculation result of the calculation unit as amplitude reduction control.

  In the above-described audio signal processing device, the reduction section starts from the time point when the amplitude value of the amplitude envelope decreases from the amplitude value at the maximum point to a value equal to or less than the first predetermined value, and the second interval from the amplitude value at the maximum point. The amplitude control unit is a section whose end point is after the return time constant has elapsed from when it has risen to a value equal to or less than a predetermined value, and the amplitude control unit performs the first predetermined value and the first as the amplitude reduction control according to the calculation result of the calculation unit. At least one of the two predetermined values is variable.

  The above audio signal processing device further includes a band dividing unit that divides the frequency band of the audio signal, and the reduction interval determination unit, the calculation unit, and the amplitude control unit are provided for each of the frequency bands divided by the band dividing unit. It is characterized in that determination, calculation of a ratio or difference of power consumption integrated values before and after amplitude control, and amplitude reduction control are performed.

  The acoustic device of the present invention is characterized by including each unit in the above-described audio signal processing device and an amplifying unit that amplifies the audio signal after amplitude reduction by the amplitude control unit.

  The control method of the audio signal processing device according to the present invention includes an amplitude control step for reducing the amplitude of an audio signal, a ratio between a power consumption integrated value before amplitude control by the amplitude control step and a power consumption integrated value after amplitude control. Alternatively, a calculation step of calculating a difference is executed, and the amplitude control step feeds back a calculation result of the calculation step and performs amplitude reduction control based on the fed back value.

  A program according to the present invention causes a computer to execute each step in the above-described method for controlling an audio signal processing device.

It is a block diagram which shows the structure of the audio equipment which concerns on 1st Embodiment. It is a block diagram which shows the structure of an audio | voice signal processing part. It is a block diagram which shows the detailed structure of an audio | voice signal processing part. It is explanatory drawing which shows an example of an amplitude envelope, and transition of the attenuation coefficient for reducing the amplitude value of the said amplitude envelope. It is explanatory drawing which shows another example of an amplitude envelope. It is a block diagram which shows the structure of the audio | voice signal processing part which concerns on 2nd Embodiment.

[First Embodiment]
Hereinafter, an audio signal processing device, an audio device, a control method for an audio signal processing device, and a program according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of the acoustic device 1 according to the first embodiment. As shown in FIG. 1, the acoustic device 1 includes an input terminal 11, an audio signal processing unit 12, a power amplifier unit 13 (amplifying unit), a power supply unit 14, and a speaker 15.

  The input terminal 11 inputs an audio signal from an external device such as a player or a personal computer. Note that an audio signal may be obtained from an external storage medium such as a USB memory or an SD memory card.

  The audio signal processing unit 12 performs analysis processing and signal processing on the input audio signal. The “audio signal processing device” in the claims corresponds to the audio signal processing unit 12.

  The power amplifier unit 13 amplifies the audio signal subjected to signal processing. In the present embodiment, it is an object to reduce power consumption in the power amplifier unit 13. For this reason, the audio signal processing unit 12 performs amplitude reduction control for reducing the amplitude value (signal level) of the audio signal. Further, in the present embodiment, it is an object to not only reduce the power consumption but also to maintain the power consumption rate (power reduction rate) at a constant value. In order to solve this, the audio signal processing unit 12 described above has a ratio of the power consumption integrated value before the amplitude reduction control and the power consumption integrated value after the amplitude reduction control (“power consumption integrated value after the amplitude reduction control” / “Power consumption integrated value before amplitude reduction control”, hereinafter referred to as “integrated value ratio”) is calculated, and amplitude reduction control is performed so that the value is constant. Details will be described later.

  The power supply unit 14 supplies power to the audio signal processing unit 12 and the power amplifier unit 13. The power supply unit 14 may be a battery, or may supply power from a commercial power source. Further, power may be supplied not only to the audio signal processing unit 12 and the power amplifier unit 13 but also to the speaker 15.

  The speaker 15 outputs the amplified audio signal. As the speaker 15, an active speaker with a built-in amplifier may be used. Further, headphones or earphones may be used instead of the speakers 15.

  Next, the configuration of the audio signal processing unit 12 will be described in detail with reference to FIG. In the present embodiment, the audio signal processing unit 12 performs an analysis process on the input audio signal of a predetermined interval (several frames to several tens of frames), and the analysis result is converted into an audio signal of the next predetermined interval. It shall be reflected in These analysis processes are performed in synchronization with the reproduction of the audio signal by the speaker 15.

  As shown in the figure, the audio signal processing unit 12 includes a reduction interval determination unit 20, an amplitude control unit 21, and a calculation management unit 22. The reduction interval determination unit 20 determines a reduction interval in which the amplitude of the audio signal (the size of the audio signal) is reduced. The amplitude control unit 21 controls the amplitude of the input audio signal according to the calculation result of the calculation management unit 22. On the other hand, the calculation management unit 22 calculates a “pre-control integrated value” that is a power consumption integrated value before performing amplitude reduction control based on a certain attenuation coefficient with respect to the audio signal for a predetermined section. That is, the “pre-control integrated value” is a power consumption integrated value that is considered to be consumed by the power amplifier unit 13 when amplitude reduction control is performed based on the attenuation coefficient at the previous calculation. In addition, the calculation management unit 22 calculates a “post-control integrated value” that is an integrated power consumption value after performing amplitude reduction control based on a certain attenuation coefficient for the audio signal of a predetermined section. That is, the “pre-control integrated value” is a power consumption integrated value that is considered to be consumed by the power amplifier unit 13 when amplitude reduction control is performed based on the attenuation coefficient at the time of the current calculation. Further, the calculation management unit 22 calculates an “integrated value ratio” that is a ratio between the “post-control integrated value” and the previously calculated “pre-control integrated value”. The amplitude control unit 21 feeds back the “integrated value ratio” that is the calculation result of the calculation management unit 22 and determines the next attenuation coefficient so that the value becomes constant. As described above, the calculation result of the calculation management unit 22 is fed back to the amplitude control unit 21 so that a constant power consumption rate can be maintained.

  Next, the configuration of the audio signal processing unit 12 will be described in more detail with reference to FIG. The reduction section determination unit 20 determines a reduction section to be subjected to amplitude reduction based on the amplitude envelope of the audio signal. The amplitude detection section 31, the maximum detection section 32, the reduction section start determination section 33, and the reduction section An end determination unit 34 is included.

  The amplitude detector 31 detects the amplitude of the input audio signal. Note that “detecting the amplitude” means detecting the amplitude value and the amplitude envelope. The “amplitude envelope” refers to the absolute value of the amplitude waveform W (see FIG. 4). In other words, it indicates a curve obtained by inverting the minus value of the amplitude, combining it with the plus value of the amplitude, and connecting the maximum values.

  The maximum detection unit 32 detects the maximum point of the amplitude envelope and the amplitude value at the maximum point (hereinafter also referred to as “maximum value”). The “maximum point” refers to the maximum position of the amplitude envelope on the time axis. For example, in the case of the amplitude envelope shown in FIG. 4 (shown, solid thick line), the local maximum detecting unit 32 detects the point P01 at which the amplitude envelope is maximum and the amplitude value thereof.

  After the maximum point is detected by the maximum detection unit 32, the reduction interval start determination unit 33 decreases the amplitude value of the amplitude envelope from the maximum value detected by the maximum detection unit 32 to a value of 6 dB (first predetermined value) or less. Is determined as the starting point of the reduction interval. That is, in the case of the example shown in FIG. 4, the point P02 is determined as the starting point of the reduction section.

  Further, after the start of the reduction interval, the reduction interval end determination unit 34 passes through the minimum point of the amplitude envelope and rises from the maximum value detected by the maximum detection unit 32 to a value equal to or less than 3 dB (second predetermined value). After the return time constant elapses from (point P03), the end point of the reduction section is determined. That is, in the example shown in FIG. 4, the point P04 is determined as the end point of the reduction section.

  Although not particularly illustrated, in the present embodiment, since the amplitude value of the amplitude envelope increases from the maximum value to a value of 3 dB or less as described above, the time after the return time constant has elapsed is determined as the end point of the reduction interval. When the maximum value of the Nth maximum point (where N is an integer satisfying N ≧ 2) is less than 3 dB from the maximum value of the (N-1) th maximum point, the Nth maximum point is also reduced. It will be included in the section. Also, the maximum value of the (N + 1) th maximum point is also included in the reduction section if it is 3 dB below the maximum value of the (N−1) th maximum point. As described above, unless a local maximum point having a local maximum value equal to or greater than “-3 dB from the local maximum value of the previously generated local maximum point” is generated, the reduction interval continues. Note that the local maximum point that is generated first is detected as a local maximum point regardless of the local maximum value, and the reduction interval start determination unit 33 and the reduction interval end determination unit 34 determine the reduction interval.

  With the above-described units 31 to 34, the reduction section determination unit 20 determines a reduction section. Hereinafter, for the sake of convenience, the reduction section will be described by dividing it into three divided sections. That is, as shown in FIG. 4, after the maximum point is detected, the reduction interval is attenuated by the attenuation coefficient from the time point when the amplitude value of the amplitude envelope decreases from the maximum value to 6 dB or less (start point of the reduction interval). “First interval” until the time constant has elapsed, “Second interval” from the end of the first interval to the time when the amplitude value of the amplitude envelope has increased from the maximum value to 3 dB or less, and the end of the second interval To the third interval from the end of the return time constant of the attenuation coefficient (end point of the reduction interval).

  Note that the first predetermined value that is a threshold value for determining the start point of the reduction section and the second predetermined value that is a threshold value for determining the end point of the reduction section are limited to the above 6 dB and 3 dB, respectively. It can be set arbitrarily. However, it is preferable that the first predetermined value is larger than the second predetermined value. As a result, the amplitude reduction control can determine a more appropriate reduction section that does not affect the sound quality and the volume perception.

  Further, although related to the above description, “a reduction interval will continue unless a local maximum having a maximum value of −3 dB or more from the local maximum of the local maximum occurs,” a reduction interval determination unit No. 20 does not necessarily need to determine the reduction interval for each detection of the maximum point of the amplitude envelope. For example, in the case of the amplitude envelope shown in FIG. 5, the first reduction section (start point: point P12, end point: point P14 after the return time constant has elapsed from point P13) is determined based on the local maximum point P11, When the second reduction section (start point: point P22, end point: point P24 after the return time constant has elapsed from point P23) is determined based on the local maximum of point P21, an overlapping section of two reduction sections occurs. . That is, in the example of FIG. 5, there is no point in detecting the maximum point of the point P21. Therefore, the maximum detection of the amplitude envelope by the maximum detection unit 43 may be performed after the end of the reduction section based on the previous maximum point.

  The amplitude control unit 21 performs amplitude reduction control on the reduction section determined by the reduction section determination unit 20, and includes an attenuation coefficient calculation unit 41 and an amplitude reduction control unit 42.

  The attenuation coefficient calculation unit 41 calculates an attenuation coefficient (amplitude attenuation coefficient) to be multiplied to reduce the amplitude value of the audio signal with respect to the reduction section. Specifically, as shown in FIG. 4, the attenuation coefficient is varied for each divided section of the reduced section. That is, since the first interval of the reduction interval is an interval corresponding to the decay time constant, the attenuation coefficient is gradually decreased from 0 dB to −2 dB. Subsequently, for the second interval, the attenuation coefficient is set to a fixed value of −2 dB (a predetermined value stored in a non-volatile memory not shown). Further, since the third interval is an interval corresponding to the return time constant, the attenuation coefficient is gradually increased from −2 dB to 0 dB.

  The amplitude reduction control unit 42 performs amplitude reduction control based on the calculation result of the attenuation coefficient calculation unit 41. That is, the amplitude value after amplitude reduction control is determined as “amplitude value after amplitude reduction control = amplitude value before amplitude reduction control × attenuation coefficient”. As a result, as shown in FIG. 4, the amplitude envelope before the amplitude reduction control (shown, solid thick line) is corrected to the amplitude envelope after the amplitude reduction control (shown, dotted thick line), and the power consumption (power) of the shaded portion shown in the figure is corrected. (Power consumption in the amplifier unit 13) can be reduced.

  Although not particularly illustrated, a delay unit that delays the input audio signal by a time required for processing from the amplitude detection by the amplitude detection unit 31 to the attenuation coefficient calculation unit 41 is separately provided, and the amplitude reduction control unit 42 Thus, amplitude reduction control may be performed on the delayed audio signal.

  On the other hand, the calculation management unit 22 includes a pre-control integrated value calculation unit 45, a post-control integrated value calculation unit 46, and an integrated value ratio calculation unit 47. The “calculation unit” in the claims corresponds to the integrated value ratio calculation unit 47.

  The pre-control integrated value calculation unit 45 includes an amplitude detection unit 51 and a power consumption calculation unit 52. The amplitude detector 51 detects the amplitude of the audio signal before the amplitude reduction control for reducing the amplitude of the audio signal for the predetermined section, that is, the input side of the amplitude controller 21. That is, when the amplitude control unit 21 performs the amplitude reduction control based on the nth attenuation coefficient (the nth calculation result of the attenuation coefficient calculation unit 41), the amplitude reduction control based on the (n-1) th attenuation coefficient is performed. Detect the amplitude of the case. In addition, the power consumption calculation unit 52 consumes the amplification of the audio signal for a predetermined section in the power amplifier unit 13 when the amplitude reduction control is not performed based on the amplitude value and the amplitude envelope detected by the amplitude detection unit 51. The “pre-control integrated value” that is the power consumption integrated value that is considered to be calculated is calculated.

  The post-control integrated value calculation unit 46 includes an amplitude detection unit 53 and a power consumption calculation unit 54. The amplitude detection unit 53 detects the amplitude of the audio signal after performing amplitude reduction control for reducing the amplitude of the output of the amplitude control unit 21, that is, the audio signal for a predetermined section. That is, the amplitude control unit 21 detects the amplitude when the amplitude reduction control based on the n-th attenuation coefficient is performed when the amplitude reduction control based on the n-th attenuation coefficient is performed. In addition, the power consumption calculation unit 54 consumes to amplify the audio signal for a predetermined section in the power amplifier unit 13 when amplitude reduction control is performed based on the amplitude value and amplitude envelope detected by the amplitude detection unit 53. An “integrated value after control” that is a power consumption integrated value that is considered to be calculated is calculated.

  The integrated value ratio calculation unit 47 calculates an “integrated value ratio” based on the calculation results of the pre-control integrated value calculation unit 45 and the post-control integrated value calculation unit 46. That is, how much power reduction rate has been achieved is calculated. The calculated “integrated value ratio” is fed back to the attenuation coefficient calculation unit 41 of the amplitude control unit 21. The attenuation coefficient calculation unit 41 calculates an attenuation coefficient for the next time (applied for the next predetermined time) based on the fed back “integrated value ratio”. For example, when the target value of the power reduction rate is “20%”, if the “integrated value ratio” is less than 80%, the power reduction rate is excessive, so the “attenuation coefficient” is reduced (for example, the second interval) The attenuation factor of the 2db to 1db). Conversely, when the “integrated value ratio” exceeds 80%, the power reduction rate has not been achieved, so the “attenuation coefficient” is increased (for example, the attenuation coefficient in the second section is changed from 2 db to 4 db). In addition, the “attenuation coefficient” may be changed from the specified value only when the power reduction rate is excessive, or the “attenuation coefficient” may be changed from the specified value only when the power reduction rate is not achieved.

  The “attenuation coefficient” may be obtained by referring to a control table (not shown) (a table in which “integrated value ratio” and “attenuation coefficient” are associated), or a predetermined algorithm (at least “integrated value ratio”). May be calculated based on an algorithm using “

  As described above, the acoustic device 1 of the present embodiment performs amplitude reduction control by feeding back the “integrated value ratio” that is the calculation result of the calculation management unit 22 to the amplitude control unit 21. That is, the audio signal before the amplitude reduction control is transmitted from the previous stage of the amplitude control unit 21 to the pre-control integrated value calculation unit 45, and the audio signal after the amplitude reduction control is transmitted from the subsequent stage of the amplitude control unit 21 to the post-control integrated value calculation unit 46. The “integrated value ratio” is calculated from the audio signals before and after the amplitude reduction control, and the calculated “integrated value ratio” is fed back to the amplitude control unit 21. Then, the amplitude control unit 21 calculates an update attenuation coefficient according to the fed back “integrated value ratio”, and performs the next amplitude reduction control. As described above, the ratio of the power consumption integrated value by the amplitude control using the pre-update attenuation coefficient and the power consumption integrated value by the amplitude control using the post-update attenuation coefficient is fed back to the amplitude control unit 21 so that the acoustic device The power consumption rate of 1 can be gradually converged to a constant value. Thereby, a constant power consumption effect can always be achieved.

  When the power consumption effect is excessive, the sound quality deterioration can be reduced by reducing the attenuation coefficient. In addition, by achieving a certain amount of power consumption in this way, in the case of the acoustic device 1 that uses a commercial power source, it is possible to expect a certain effect of reducing electricity charges. In addition, in the case of the acoustic device 1 driven by a battery (battery), an effect of extending a certain driving time can be expected, and as a result, the remaining usage time can be calculated more accurately.

  In the present embodiment, the reduction section to be subjected to amplitude reduction control is determined based on the maximum point and maximum value of the amplitude envelope. In other words, sections that are less likely to affect the sound quality and volume of sound are determined as reduced sections, and the amplitude value is not changed in sections other than the reduced sections that are more likely to be affected.Therefore, power consumption is maintained without sacrificing sound quality or volume. Can be reduced. Further, even when an audio signal whose band is limited to the reproducible frequency band of the speaker 15 is input to the power amplifier unit 13 as in a current battery-driven active speaker system, a power saving effect can be exhibited. it can.

  Further, the reduction interval is determined with the time point when the amplitude value of the amplitude envelope decreases from the maximum value to a value of 6 dB or less as the start point, and the time point after the return time constant elapses from the time point when the amplitude value increases from the maximum value to 3 dB or less. Therefore, even after detecting a local maximum point, even if a local maximum point having a maximum value lower than 3 dB from the amplitude value of the local maximum point is detected, the reduction interval does not end. In other words, instead of determining all reduction points except for all the maximum points included in the amplitude envelope, the maximum points that are judged to be less likely to affect the sound quality and volume feeling are included in the reduction interval. Thus, power consumption can be reduced more efficiently.

  In addition, since the first predetermined value serving as the threshold value for the start point of the reduction section is larger than the second predetermined value serving as the threshold value for the end point, the auditory influence when performing the amplitude reduction control is reduced. can do. Furthermore, with respect to the “second section” of the reduction section, by setting the attenuation coefficient to a fixed value, it is possible to reduce the control load required for attenuation coefficient calculation control.

In addition, the following modifications can be employed.
[Modification 1]
In the above embodiment, a first predetermined value that is a threshold value for determining the start point of the reduction interval and a second predetermined value that is a threshold value for determining the end point of the reduction interval are each set to a fixed value ( 6 dB and 3 dB), but may be variable. For example, the first predetermined value and / or the second predetermined value may be varied in accordance with the amplitude value (maximum value) of the maximum point serving as a reference for determining the reduction interval. In this case, when the maximum value is small, it is easy to feel a sense of volume due to amplitude reduction. Therefore, it is preferable to increase the first predetermined value and / or the second predetermined value in order to shorten the reduction section. On the other hand, when the maximum value is large, it is difficult to feel a decrease in volume feeling due to amplitude reduction. Therefore, it is preferable to decrease the first predetermined value and / or the second predetermined value in order to lengthen the reduction section.

[Modification 2]
The user may be able to set / change the first predetermined value and / or the second predetermined value and the default value (initial value) of the attenuation coefficient in the “second interval”. In this case, it is assumed that the sound device 1 is provided with operation means (not shown) such as an operation panel or a remote controller. In addition, an audio signal analyzing means (not shown) is provided, and the first predetermined value and / or the first value are determined according to the analysis result (music feature such as music genre, music tempo, music key (KEY), etc.). The predetermined value of 2 and the default value of the attenuation coefficient may be variably set. When the first predetermined value and the second predetermined value are variable values according to the maximum value or the analysis result, or set by the user, “first predetermined value> second predetermined value” As such, the setting range may be limited.

[Modification 3]
Further, in the above embodiment, as a method of determining the reduction interval, the time point (point P01 in FIG. 4) when the amplitude value of the amplitude envelope decreases from the maximum value to 6 dB or less (start point), and the value from the maximum value to 3 dB or less. Although the method of ending after the elapse of the return time constant (point P04 in FIG. 4) from the point of time until the point is reached is exemplified, the reduction interval may be determined by other methods. For example, in the example of FIG. 4, the point P03 may be the end point of the reduction section.

  In addition, for example, regardless of the amplitude values before and after the maximum point, a section excluding the predetermined time before and after the maximum point may be determined as the reduction section. In this case, the pre-predetermined time and the post-predetermined time may be the same time or different times. Further, the pre-predetermined time and the post-predetermined time may be variably set according to the maximum value, or may be a time set by the user. Furthermore, the pre-predetermined time and the post-predetermined time may be variably set according to the analysis result of the audio signal.

  In this case, the maximum point may be detected. For example, the local maximum point may be detected on condition that the local maximum value of the local maximum point to be detected is equal to or greater than the local maximum value that is the reference of the immediately preceding reduction interval. Further, as in the above-described embodiment, the maximum value of the local maximum point to be detected is less than the second predetermined value (for example, 3 dB) from the local maximum value serving as the reference of the immediately preceding reduction section. The maximum point may be detected on the condition that it is large.

[Modification 4]
In the above embodiment, the attenuation coefficient is made variable in accordance with the calculation result of the integrated value ratio calculation unit 47. However, the attenuation coefficient may be made variable instead of making the attenuation coefficient variable. . In other words, when the target value of the power reduction rate is “20%”, if the “integrated value ratio” is less than 80%, the power reduction rate is excessive, and therefore the “reduction section” is shortened. Conversely, if the “integrated value ratio” exceeds 80%, the power reduction rate has not been achieved, so the “reduction section” is lengthened. That is, according to the calculation result of the integrated value ratio calculation unit 47, the first predetermined value and / or the second predetermined value in the above-described embodiment can be varied, or the previous predetermined time in [Modification 3] and / or Alternatively, the length of the “reduction section” may be changed by changing the predetermined time later. According to this configuration, a constant power consumption rate can be achieved without changing the attenuation coefficient. However, in this case, the calculation result of the integrated value ratio calculation unit 47 is fed back not only to the amplitude control unit 21 but also to the reduction interval determination unit 20.

[Modification 5]
Further, in the above embodiment, the ratio between the “pre-control integrated value” and the “post-control integrated value” is calculated by the integrated value ratio calculating unit 47, but the difference may be calculated. In this case, the target value of power reduction amount is defined as “XXW (Watt)”, etc., and the power reduction amount obtained by (“pre-control integrated value” − “post-control integrated value”) exceeds the target value Since the power reduction rate is excessive, the “attenuation coefficient” is reduced or the “reduction interval” is shortened. On the other hand, if it is below the target value, the power reduction rate has not been achieved, so the “attenuation coefficient” is increased or the “reduction section” is lengthened. According to this configuration, a certain amount of power consumption can be achieved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that a reduction section is determined, an integrated value ratio is calculated, and amplitude reduction control is performed for each divided band obtained by dividing the frequency band of the audio signal. Only differences from the first embodiment will be described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Moreover, the modification applied about the component similar to 1st Embodiment is applied similarly about this embodiment.

  FIG. 6 is a block diagram illustrating a configuration of the audio signal processing unit 12 according to the second embodiment. The audio signal processing unit 12 according to the present embodiment includes a band dividing unit 70 that divides a frequency band into a low band, a middle band, and a high band, and three reduction section determination units that determine a reduction section for each divided band. 60a, 60b, and 60c, three amplitude control units 61a, 61b, and 61c that perform amplitude reduction control for each divided band, and three calculation management units 62a and 62b that calculate an integrated value ratio for each divided band. 62c and an adder 63 for adding the audio signals of the respective divided bands after the amplitude reduction control.

  In order to divide the frequency band, the band dividing unit 70 uses a Linkwitz-Riley filter in which two Butterworth filters whose cutoff frequency is attenuated by 3 dB are connected in cascade. Specifically, a first Linkwitz-Riley filter 71 in which two stages of fc = 200 Hz and a second-order LPF (Low pass filter) are cascade-connected is used as a low-frequency division filter. Further, as a mid-band division filter, fc = 200 Hz, a second Linkwitz-Riley filter 72 in which a second-order HPF (High pass filter) is cascade-connected, and fc = 2 kHz, a second-order LPF is cascaded in two stages. A connected third Linkwitz-Riley filter 73 is used. Further, a fourth Linkwitz-Riley filter 74 in which fc = 2 kHz and second-order HPFs are cascade-connected is used as a high-frequency division filter.

  Thus, by using the Linkwitz-Riley filter, the frequency amplitude characteristic becomes flat when the frequency band is divided and then synthesized by the adder 63. That is, the frequency amplitude characteristic of the output signal synthesized by the adding unit 63 matches the frequency amplitude characteristic of the input signal input to the audio signal processing unit 12.

  Moreover, each reduction area determination part 60a, 60b, 60c functions similarly to the reduction area determination part 20 of 1st Embodiment, and determines a reduction area with respect to each division band. Each calculation management unit 62a, 62b, and 62c functions in the same manner as the calculation management unit 22 of the first embodiment, and calculates an integrated value ratio for each divided band. Each amplitude control unit 61a, 61b, 61c functions in the same manner as the amplitude control unit 21 of the first embodiment, and calculates the attenuation coefficient by feeding back the calculated integrated value ratio of each divided band. Amplitude reduction control is performed based on the attenuation coefficient. Further, the adder 63 synthesizes the audio signal after the amplitude reduction control by the amplitude controllers 61a, 61b, 61c.

  As described above, the acoustic device 1 according to the present embodiment performs determination of a reduction section, calculation of an integrated value ratio, calculation of an attenuation coefficient, and amplitude reduction control after frequency band division. As a result, the reduction interval is different for each divided band, and the amplitude reduction effect is distributed on the time axis, so that the auditory influence by the amplitude reduction control can be further reduced.

  In the second embodiment described above, the band is divided into three bands, a low band, a middle band, and a high band. However, the number of divisions and the division frequency are arbitrarily determined, such as dividing each divided band into a plurality of bands. It can be set. Further, the number of divisions and the division frequency may be set and changed by the user, or may be variably set according to the analysis result of the audio signal.

  As mentioned above, although two embodiment and various modifications were shown, it is possible to provide each component of acoustic device 1 shown in each embodiment and each modification as a program. Further, the program can be provided by being stored in various recording media (CD-ROM, flash memory, etc.). That is, a program for causing a computer to function as each component of the audio device 1 and a recording medium on which the program is recorded are also included in the scope of rights of the present invention.

  In the above-described embodiment, the case where the audio signal processing unit 12 is applied to the acoustic device 1 is exemplified. However, the audio signal processing unit 12 may be applied to various electronic musical instruments, computers (PC applications), cloud computing, and the like. Other modifications can be made as appropriate without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Acoustic apparatus 11 ... Input terminal 12 ... Audio | voice signal processing part 13 ... Power amplifier part 14 ... Power supply part 15 ... Speaker 20 ... Reduction area determination part 21 ... Amplitude control part 22 ... Calculation management part 31 ... Amplitude detection part 32 ... Maximum Detection unit 33 ... Reduction interval start determination unit 34 ... Reduction interval end determination unit 41 ... Attenuation coefficient calculation unit 42 ... Amplitude reduction control unit 43 ... Maximum detection unit 45 ... Pre-control integration value calculation unit 46 ... Post-control integration value calculation unit 47 ... Integral value ratio calculation unit 51 ... Amplitude detection unit 52 ... Power consumption calculation unit 53 ... Amplitude detection unit 54 ... Power consumption calculation unit 60a-60c ... Reduction section determination unit 61a-61c ... Amplitude control unit 62a-62c ... Calculation management unit 63 ... Adding unit 70 ... Band division unit 71-74 ... Linkwitz-Riley filter W ... Amplitude waveform

Claims (9)

An amplitude controller that reduces the amplitude of the audio signal;
A calculation unit that calculates a ratio or difference between the power consumption integrated value before amplitude control by the amplitude control unit and the power consumption integrated value after amplitude control;
The amplitude control unit feeds back a calculation result of the calculation unit, and performs amplitude reduction control based on the fed back value.   The audio signal processing apparatus according to claim 1, wherein the amplitude control unit performs amplitude reduction control so that a calculation result of the calculation unit becomes a constant value. A reduction interval determination unit that determines a reduction interval for reducing the amplitude of the audio signal based on the maximum point of the amplitude envelope of the audio signal;
The audio signal processing apparatus according to claim 1, wherein the amplitude control unit performs amplitude reduction control on the reduction interval determined by the reduction interval determination unit.   The audio signal processing apparatus according to claim 3, wherein the amplitude control unit varies an amplitude attenuation coefficient of the reduction section according to a calculation result of the calculation unit as the amplitude reduction control. The reduction section starts when the amplitude value of the amplitude envelope falls from the amplitude value at the local maximum point to a value equal to or lower than a first predetermined value, and is equal to or lower than the second predetermined value from the amplitude value at the local maximum point. It is an interval that ends after the return time constant elapses from the time when the value rises to
4. The amplitude control unit according to claim 3, wherein the amplitude control unit varies at least one of the first predetermined value and the second predetermined value according to a calculation result of the calculation unit as the amplitude reduction control. Audio signal processing device. Further comprising a band dividing unit for dividing the audio signal into frequency bands,
The reduction interval determination unit, the calculation unit, and the amplitude control unit determine the reduction interval and calculate the ratio or difference of the power consumption integrated values before and after the amplitude control for each frequency band divided by the band dividing unit. The audio signal processing apparatus according to claim 3, wherein amplitude reduction control is performed. Each unit in the audio signal processing device according to any one of claims 1 to 6,
An acoustic device comprising: an amplification unit that amplifies an audio signal after amplitude reduction by the amplitude control unit. An amplitude control step for reducing the amplitude of the audio signal;
Performing a calculation step of calculating a ratio or difference between the power consumption integrated value before amplitude control by the amplitude control step and the power consumption integrated value after amplitude control;
The method of controlling an audio signal processing device, wherein the amplitude control step feeds back a calculation result of the calculation step and performs amplitude reduction control based on the fed back value.   The program for making a computer perform each step in the control method of the audio | voice signal processing apparatus of Claim 8.

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