Sound control device

Abstract

In the present invention, if an input waveform (Win) includes an excess portion (EX) in which the absolute value of a level (Lv) exceeds a limiter threshold value (Th), then an absolute value waveform generation unit (S03) generates an absolute value waveform (Wab) obtained by converting the level into the absolute value of the level in the input waveform. A peak retention waveform generation unit (S04) generates a peak retention waveform (Wp) on the basis of the absolute value waveform. A gain curve generation unit (S05) generates a gain curve (Wgn) indicating the relationship between a gain (Gn) obtained on the basis of the level in the peak retention waveform and an input waveform time (Tm). A smoothing processing unit (S06) obtains, by smoothing processing, a smooth gain curve (Wsgn) based on the gain curve. A sound production data generation unit (S07, S08) generates sound production data by multiplying a delay input waveform (Wind), in which the input waveform is shifted to the time plus side (Dtp), by the smooth gain curve.

Description

Cross - reference to related applications , ,

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[0001] This application is based on Japanese Patent Application No. 2023 - 44827 filed on March 21, 2023, the contents of which are incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to a pronunciation control device used to cause a sounding body to produce sound.

Background Art

[0003] For example, a vehicle approach notification device described in Patent Document 1 has been conventionally known. This vehicle approach notification device includes a function of generating pronunciation data for causing a sounding body such as a speaker to produce sound. The vehicle approach notification device described in this Patent Document 1 is mounted on an automobile such as a hybrid vehicle or an electric vehicle. For example, the vehicle approach notification device may mix an approach notification sound for notifying a pedestrian around the automobile that the automobile is approaching during low - speed driving and a back warning sound for notifying the back state in which the automobile is backing up, and cause them to be emitted from one sounding body simultaneously.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A pronunciation system (for example, the vehicle approach notification device of Patent Document 1) in which a sounding body produces sound based on pronunciation data includes a digital - to - analog converter and a power amplifier that process a sound signal input to the sounding body such as a speaker. Allowable input / outputs are set for each of these digital - to - analog converters and power amplifiers. Also, an allowable input / output is set for the sounding body. Therefore, in a sound generation system, the sound generation control device that generates sound generation data needs to keep the input and output signals of acoustic devices such as digital-to-analog converters, power amplifiers, and sound-producing elements below the allowable input and output limits, and to make effective use of those allowable input and output limits.

[0006] In response to this, one might consider limiting the input and output signals of an audio device to below the permissible input / output limits by simply restricting waveform peaks. However, such a simple restriction of waveform peaks results in harmonic distortion caused by waveform bending, leading to the generation of abnormal noise due to this harmonic distortion. The inventors found this to be the case after detailed investigation.

[0007] In view of the above, this disclosure aims to provide a sound generation control device that can limit the amplitude of the waveform in sound generation data while suppressing abnormal sounds such as harmonic distortion caused by the amplitude limitation of the waveform.

[0008] To achieve the above objective, according to one aspect of this disclosure, the sound control device is: A sound control device that generates sound data, which is included in a sound system in which a sound-producing body produces sound according to a sound signal based on sound data representing a sound waveform, An over-determination unit acquires an input waveform that is the basis of the sound generation data, which is a waveform showing the relationship between the level corresponding to the voltage of the sound generation signal and time, and determines whether or not the input waveform contains an excess portion in which the absolute value of the level exceeds a predetermined limiter threshold. If the excess detection unit determines that the input waveform contains an excess portion, the absolute value waveform generation unit generates an absolute value waveform obtained by converting the level in the input waveform to the absolute value of that level. A peak-holding waveform generation unit generates a peak-holding waveform that shows the relationship between the level and the input waveform time, which is the time in the input waveform, based on the absolute value waveform. A gain curve generation unit generates a gain curve that shows the relationship between the gain obtained based on the level in the peak-holding waveform and the input waveform time, A smoothing processing unit that obtains a smooth gain curve based on the gain curve by performing a smoothing process to smooth the gain curve, The system includes a sound generation data generation unit that generates sound generation data by multiplying a delayed input waveform, which is shifted by a predetermined waveform delay time toward the time-positive side (the side where the input waveform time has elapsed in the time axis direction), with a smooth gain curve. The peak-holding waveform is a waveform aggregate composed of an absolute value waveform, peak-holding sections provided at each maximum level point of the absolute value waveform, extending linearly from each maximum point to the time-positive side for a predetermined peak-holding time, showing the same level as the maximum point until reaching the absolute value waveform, and release sections provided at each peak-holding section that extends over the peak-holding time, extending from the time-positive end of the peak-holding section, moving towards the lower level side as time progresses, until reaching the absolute value waveform. The waveform shape is obtained by extracting the outer shape formed on the higher level side of this waveform aggregate. The gain of the gain curve is set to 1 in the time axis range where the level in the peak-holding waveform is below the limiter threshold, and in the time axis range where the level in the peak-holding waveform exceeds the limiter threshold, the gain is set to a value obtained from "Gn = Th / Lv", where the gain is Gn, the level is Lv, and the limiter threshold is Th. The smooth gain curve is designed so that, relative to the gain curve, the gain lag shifts in the positive time direction when comparing the peak portions where the gain is maximum or minimum. The waveform delay time is greater than or equal to the gain delay time, and the peak holding time is greater than or equal to the waveform delay time.

[0009] In this way, sound data is generated based on the input waveform. Simultaneously, by multiplying the delayed input waveform by the smoothing gain curve, it is possible to limit the amplitude of the waveform represented by the sound data to below the limiter threshold. Since the waveform of the amplitude-limited sound data is smoothly formed, it is possible to suppress abnormal noises such as harmonic distortion caused by amplitude limitation.

[0010] In addition, each element in the application documents may be given a reference numeral in parentheses. In this case, the reference numeral merely indicates one example of the correspondence between the element and the specific configuration described in the embodiments described later. Therefore, this disclosure is not limited in any way by the inclusion of such reference numerals. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the schematic configuration of the sound generation system in the first embodiment. [Figure 2] This is a flowchart showing the control process performed by the limiter unit included in the sound generation system of the first embodiment. [Figure 3] This figure shows the input waveform to the limiter section in (a), the absolute value waveform and peak-holding waveform in (b), and the gain curve in (c), with the time axes of each Cartesian coordinate system aligned with each other. [Figure 4] This diagram shows the waveform set and absolute value waveform that form the basis of the peak-holding waveform. [Figure 5] This figure shows the gain curves in (a) and the smoothed gain curve obtained by smoothing the gain curves while aligning the time axes of each Cartesian coordinate system. [Figure 6] This figure shows the smooth gain curve in (a), the delayed input waveform in (b), and the waveform represented by the sound generation data in (c), with the time axes of each Cartesian coordinate system aligned with each other. [Modes for carrying out the invention]

[0012] The embodiments will be described below with reference to the drawings. In the following embodiments, including other embodiments described later, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings.

[0013] (First Embodiment) In this embodiment, the pronunciation system 8 shown in FIG. 1 is a vehicle approach notification device mounted on, for example, a hybrid vehicle or an electric vehicle. For example, the pronunciation system 8 is electrically connected to a sounding body 80 such as a speaker or a buzzer. Then, the pronunciation system 8 outputs various alarm sounds such as a vehicle approach notification sound for notifying the surroundings that an automobile having the pronunciation system 8 is approaching and other notification sounds from the sounding body 80.

[0014] The pronunciation system 8 includes a microcomputer 10, a digital-to-analog converter 12, and a power amplifier 14. In the description of this embodiment, the digital-to-analog converter 12 is also referred to as DAC12, and the power amplifier 14 is also referred to as AMP14.

[0015] The microcomputer 10 outputs pronunciation data Dsd generated by the microcomputer 10 to the DAC12. The DAC12 converts the pronunciation data Dsd input from the microcomputer 10 into a pronunciation signal Ssa which is an analog signal, and outputs the pronunciation signal Ssa to the AMP14. Note that the pronunciation data Dsd, output waveform data DW, first synthesized waveform data D1m, and second synthesized waveform data D2m described later are digital data representing the waveform of sound (for example, a PCM waveform).

[0016] Based on the voltage application from a constant voltage source (not shown), the AMP14 causes a current corresponding to the pronunciation signal Ssa input from the DAC12 to the AMP14 to flow through the sounding body 80. The sounding body 80 sounds according to the supply of the current from the AMP14. That is, the sounding body 80 sounds according to the pronunciation signal Ssa based on the pronunciation data Dsd. In this embodiment, the circuit gain of the acoustic circuit between the microcomputer 10 and the sounding body 80, that is, the circuit gain of the acoustic circuit composed of the DAC12 and the AMP14 is, for example, constant.

[0017] The microcomputer 10, which is an electronic control unit in other words, is configured as an in-vehicle microcomputer including a CPU, a RAM, a ROM, a non-volatile rewritable memory, etc. not shown in the figures. That is, the microcomputer 10 reads and executes a computer program stored in a ROM or a non-volatile rewritable memory, which is a non-transitory tangible recording medium. When this computer program is executed, a method corresponding to the computer program is executed. That is, in the microcomputer 10, various control processes such as the control process shown in FIG. 2 executed by a limiter unit 26, which will be described later and is included in the microcomputer 10, are executed according to the computer program.

[0018] As shown in FIG. 1, the microcomputer 10 functionally includes a plurality of sound source control units 16, a mixing unit 22, an equalizer unit 24, and a limiter unit 26.

[0019] Each of the plurality of sound source control units 16 selects one or a plurality of sound source data from a plurality of sound source data prestored in a storage medium such as a ROM according to a vehicle state signal. Then, the sound source control unit 16 generates output waveform data DW based on each selected sound source data by performing pitch control and volume control on each selected sound source data, and outputs the output waveform data DW to the mixing unit 22. The vehicle state signal is a signal indicating the state of an automobile equipped with the sound generating system 8 (for example, the driving situation of the automobile, the remaining amount of fuel, the situation around the automobile, etc.), and is input to the microcomputer 10 from various sensors of the automobile, for example.

[0020] Among the plurality of sound source control units 16, for example, the sound source control unit 16 that selects the sound source data reproduced as a vehicle approach notification sound performs pitch control and volume control on the selected sound source data. On the other hand, among the sound source control units 16, for example, the sound source control unit 16 that selects the sound source data reproduced as other notification sounds that are not vehicle approach notification sounds performs volume control without performing pitch control on the selected sound source data.

[0021] The mixing unit 22 mixes multiple output waveform data DW input to the mixing unit 22 from multiple sound source control units 16. The mixing unit 22 then outputs the first combined waveform data D1m, which is the waveform data after mixing, to the equalizer unit 24. In other words, the mixing unit 22 outputs the first combined waveform data D1m, which is synthesized from multiple output waveform data DW, to the equalizer unit 24.

[0022] The equalizer unit 24 generates a second composite waveform data D2m based on the first composite waveform data D1m by correcting its acoustic characteristics, and outputs the second composite waveform data D2m to the limiter unit 26. For example, the filter characteristics of the equalizer unit 24 are determined by the filter type, center frequency, gain, and filter width. The degree of change of the second composite waveform data D2m relative to the first composite waveform data D1m varies greatly depending on the combination of the first composite waveform data D1m and the filter characteristics of the equalizer unit 24, making it difficult to predict the amplitude peak of the digital waveform represented by the second composite waveform data D2m.

[0023] The filter type described above is selected by, for example, a known technique. Examples of the types of filters that can be selected include low-pass filters, high-pass filters, band-pass filters, notch filters, low-shelf filters, high-shelf filters, and peaking filters.

[0024] The limiter unit 26 limits the amplitude of the digital waveform represented by the sound data Dsd to below a predetermined limiter threshold Th, and outputs the amplitude-limited sound data Dsd to the DAC12. The limiter threshold Th corresponds to the allowable input of the sound generator 80 and AMP14, and the full range of the DAC12. For example, the limiter threshold Th is experimentally set in advance to be as large as possible within a range that allows the input signal voltage of the sound generator 80 and AMP14 to be kept below the allowable input, and the waveform amplitude of the sound data Dsd input to the DAC12 to be kept below the full range of the DAC12.

[0025] In order to limit the amplitude of the sound data Dsd, the limiter unit 26, in order to output the sound data Dsd to the DAC 12, pre-reads the second synthesized waveform data D2m input from the equalizer unit 24 and executes the control process shown in Figure 2. This control process in Figure 2 is executed repeatedly, for example, when the second synthesized waveform data D2m is input to the limiter unit 26. The limiter unit 26 corresponds to the sound control device of this disclosure.

[0026] As shown in Figure 2, the limiter unit 26 first acquires the input waveform Win in step S01. This input waveform Win is a digital waveform represented by the second synthesized waveform data D2m input from the equalizer unit 24 to the limiter unit 26, and is the basis for the sound output data Dsd from the limiter unit 26 to the DAC 12. In addition to the input waveform Win, the waveforms and curves generated based on the input waveform Win in steps S03 to S09 described later are also digital waveforms.

[0027] Furthermore, as shown in Figure 3(a), the input waveform Win is a waveform that shows the relationship between level Lv and time Tm. The level Lv corresponds to the voltage of the analog signal Ssa, and the amplitude of level Lv corresponds to the voltage amplitude of the signal Ssa. In the description of this embodiment, the time Tm on the horizontal axis of the input waveform Win is sometimes referred to as the input waveform time Tm. After step S01 in Figure 2, the process proceeds to step S02.

[0028] In step S02, as shown in Figure 3(a), the limiter unit 26 determines whether the input waveform Win contains an excess portion EX where the absolute value of the level Lv exceeds the limiter threshold Th. The input waveform Win shown in Figure 3(a) contains three excess portions EX.

[0029] In step S02 of Figure 2, if it is determined that the input waveform Win contains the excess portion EX, the process proceeds to step S03. On the other hand, if it is determined that the input waveform Win does not contain the excess portion EX, the process proceeds to step S09.

[0030] In step S03, as shown in Figure 3(b), the limiter unit 26 generates an absolute value waveform Wab by converting the vertical axis level Lv of the input waveform Win into the absolute value of that level Lv. In other words, the absolute value waveform Wab is a waveform obtained by inverting the negative portion of the input waveform Win where the level Lv is a negative value towards the positive side of the level Lv, using the zero position of the level Lv as a reference, and combining it with the waveform of the positive portion of the input waveform Win where the level Lv is a positive value. After step S03 in Figure 2, the process proceeds to step S04.

[0031] In step S04, as shown in Figures 3(b) and 4, the limiter unit 26 generates a peak-holding waveform Wp, which shows the relationship between the level Lv and the input waveform time Tm, based on the absolute value waveform Wab.

[0032] In this embodiment, in a Cartesian coordinate system with the level Lv as the vertical axis and the input waveform time Tm as the horizontal axis, the side of the input waveform time Tm that is elapsed along the horizontal axis (time axis Dt) is referred to as the time-positive side Dtp, and the side of the input waveform time Tm that is regressing is referred to as the time-negative side Dtm. Furthermore, in the same Cartesian coordinate system, the side of the level Lv that is higher along the vertical axis (level axis DL) is referred to as the high-level side DLp, and the side of the level Lv that is lower is referred to as the low-level side DLm. Also, for confirmation, the absolute value waveform Wab shown in Figure 3(b) and the absolute value waveform Wab shown in Figure 4 are the same.

[0033] Specifically, in order to obtain a peak-holding waveform Wp, the limiter unit 26 first generates a waveform assembly 30 consisting of an absolute value waveform Wab, one or more peak-holding units 32, and one or more release units 33, as shown in Figure 4.

[0034] The peak holding sections 32 included in the waveform set 30 are provided at every 28 maximum level points Lv in the absolute value waveform Wab. In other words, the number of peak holding sections 32 is equal to the number of maximum level points Lv 28 in the absolute value waveform Wab.

[0035] The peak holding section 32 extends linearly from the maximum level point 28 to the time-positive side Dtp, parallel to the time axis Dt. More specifically, the peak holding section 32 extends linearly from the maximum level point 28, which is the starting point, to the time-positive side Dtp, for a predetermined peak holding time Ht, until it reaches the absolute value waveform Wab, while exhibiting the same level Lv as the maximum level point 28.

[0036] For example, if the peak holding section 32 extends from the maximum point 28 and reaches any point in the absolute value waveform Wab before reaching the length over the peak holding time Ht, the length of the peak holding section 32 will be less than the length over the peak holding time Ht. On the other hand, if the peak holding section 32 extends from the maximum point 28 and reaches the length over the peak holding time Ht without intersecting the absolute value waveform Wab, the length of the peak holding section 32 will be the length over the peak holding time Ht. The peak holding time Ht is, for example, a constant value and is preset to be as short as possible within the range that can limit the amplitude of the waveform represented by the sound generation data Dsd to below the limiter threshold Th.

[0037] The release section 33 included in the waveform assembly 30 is provided for each peak holding section 32 that extends over the peak holding time Ht. That is, the release section 33 is provided for peak holding sections 32 whose length in the time axis direction Dt reaches the length over the peak holding time Ht, but not for peak holding sections 32 whose length in the time axis direction Dt is less than the length over the peak holding time Ht. Therefore, the number of release sections 33 is equal to the number of peak holding sections 32 whose length in the time axis direction Dt reaches the length over the peak holding time Ht.

[0038] The release section 33 starts from the extended end 32a, which is the time-positive end Dtp of the peak holding section 32, which has a length over the peak holding time Ht, and extends from the extended end 32a toward the lower level DLm by the time-positive Dtp, until it reaches any point in the absolute value waveform Wab. The slope of the release section 33 in the orthogonal coordinate system of level Lv and input waveform time Tm may be constant, or it may become steeper as it moves away from the starting point, the extended end 32a. The slope of the release section 33 is set in advance to avoid the unnatural sound caused by limiting the amplitude of the waveform represented by the sound generation data Dsd to below the limiter threshold Th.

[0039] As shown in Figures 3(b) and 4, the limiter unit 26 extracts the high-level outer shape 301, which is the outer shape formed on the high-level side DLp of the waveform assembly 30 formed as described above, and uses the shape of the extracted high-level outer shape 301 as the waveform shape of the peak-holding waveform Wp. In other words, the limiter unit 26 determines the peak-holding waveform Wp so that its waveform shape is the same as the shape of the high-level outer shape 301 of the waveform assembly 30. In short, the peak-holding waveform Wp generated in step S04 is determined to have the same waveform shape as the high-level outer shape 301 of the waveform assembly 30. The time width occupied by the release portion 33 in the time axis direction Dt of the peak-holding waveform Wp is called the release time Rt. After step S04 in Figure 2, the process proceeds to step S05.

[0040] In step S05, as shown in Figure 3(c) and Figure 5(a), the limiter unit 26 generates a gain curve Wgn that shows the relationship between the gain Gn obtained based on the level Lv in the peak-holding waveform Wp and the input waveform time Tm.

[0041] In this embodiment, in a Cartesian coordinate system with gain Gn on the vertical axis and input waveform time Tm on the horizontal axis, the side of the gain axis Dgn (the vertical axis) where gain Gn is large is referred to as the high-gain side Dgnp, and the side where gain Gn is small is referred to as the low-gain side Dgnm. Furthermore, in the Cartesian coordinate system of gain Gn and input waveform time Tm, the direction of the time axis Dt is indicated by the time-positive side Dtp and the time-negative side Dtm, similar to the Cartesian coordinate system of level Lv and input waveform time Tm described above. In this embodiment, both the description and the figures may show the gain Gn as a value or as a percentage.

[0042] Specifically, the gain Gn of the gain curve Wgn is set to 1 in the time axis range R1t, R2t (i.e., within the threshold range R1t, R2t) where the level Lv in the peak-holding waveform Wp is less than or equal to the limiter threshold Th.

[0043] On the other hand, the gain Gn of the gain curve Wgn is set to the value obtained from the following equation F1 in the range R3t and R4t in the time axis direction Dt where the level Lv in the peak-holding waveform Wp exceeds the limiter threshold Th (i.e., the threshold-exceeding ranges R3t and R4t). The threshold-exceeding ranges R3t and R4t are the range obtained by subtracting the threshold-in-range ranges R1t and R2t from the width that the peak-holding waveform Wp occupies in the time axis direction Dt. In the following equation F1, Gn is the gain Gn of the gain curve Wgn, Th is the limiter threshold Th, and Lv is the level Lv in the peak-holding waveform Wp. After step S05 in Figure 2, proceed to step S06. Gn = Th / Lv ···(F1)

[0044] In step S06, as shown in Figures 5(a) and 5(b), the limiter unit 26 obtains a smoothed gain curve Wsgn based on the gain curve Wgn by performing a smoothing process to smooth the gain curve Wgn. For example, this smoothing process is performed by passing the gain curve Wgn through a double moving average filter, a Bessel filter, or a Thiran low-pass filter.

[0045] For confirmation, the gain curve Wgn shown in Figure 3(c) and the gain curve Wgn shown in Figure 5(a) are the same. Furthermore, the smooth gain curve Wsgn shown in Figure 6(a) and the smooth gain curve Wsgn shown in Figure 5(b) are the same.

[0046] More specifically, the smooth gain curve Wsgn obtained in step S06 is designed so that, relative to the gain curve Wgn, the gain delay time St is shifted to the time-positive side Dtp when comparing the peak portions 36a and 37a where the gain Gn is at its maximum or minimum. This gain delay time St is a constant value.

[0047] For example, in the time axis direction Dt, the center time T1 of one peak portion 36a included in the gain curve Wgn is compared with the center time T2 of the peak portion 37a in the smooth gain curve Wsgn that corresponds to the peak portion 36a of the gain curve Wgn. In this case, the center time T2 of the peak portion 37a of the smooth gain curve Wsgn is shifted by a gain delay time St toward the time-positive side Dtp relative to the center time T1 of the peak portion 36a of the gain curve Wgn. This is also true when other peak portions 36a and 37a are compared between the gain curve Wgn and the smooth gain curve Wsgn. After step S06 in Figure 2, the process proceeds to step S07.

[0048] In step S07, as shown in Figure 6(b), the limiter unit 26 generates a delayed input waveform Windd, which is the input waveform Win shifted by a predetermined waveform delay time D to the time-positive side Dtp in the time axis direction Dt. The waveform delay time D is, for example, a constant value. In other words, the delayed input waveform Windd is a waveform obtained by parallel shifting the input waveform Win to the time-positive side Dtp by a waveform delay time D.

[0049] The relative magnitudes of the gain delay time St, waveform delay time D, and peak holding time Ht are "St ≤ D ≤ Ht". For example, in this embodiment, the gain delay time St, waveform delay time D, and peak holding time Ht are "St = D = Ht = 1 msec". After step S07 in Figure 2, the process proceeds to step S08.

[0050] In step S08, as shown in Figures 6(a) to (c), the limiter unit 26 generates sound data Dsd by multiplying the delayed input waveform Wind and the smooth gain curve Wsgn. In other words, generating sound data Dsd by multiplying the delayed input waveform Wind and the smooth gain curve Wsgn means that the product of the level Lv of the delayed input waveform Wind and the gain Gn of the smooth gain curve Wsgn is calculated, and this calculated product is the level Lv of the waveform Wsd represented by the sound data Dsd. The limiter unit 26 outputs the sound data Dsd generated in step S08 to the DAC12.

[0051] By going through the processes described in steps S03 to S08 above, the limiter unit 26 can obtain sound-producing data Dsd with suppressed waveform distortion by continuously adjusting the gain Gn while keeping the amplitude of the waveform Wsd represented by the sound-producing data Dsd below the limiter threshold Th. However, the waveform Wsd represented by the sound-producing data Dsd output by the limiter unit 26 will have a time delay of waveform delay time D relative to the input waveform Win.

[0052] In step S09 of Figure 2, the limiter unit 26 outputs the sound-producing data Dsd at its original level Lv, without suppressing the level Lv of the waveform Wsd represented by the sound-producing data Dsd, relative to the level Lv of the input waveform Win acquired in step S01.

[0053] The processing in each step of Figure 2 described above constitutes a functional unit that realizes its respective function. Specifically, steps S01 and S02 correspond to the over-detection unit, step S03 corresponds to the absolute value waveform generation unit, step S04 corresponds to the peak-holding waveform generation unit, and step S05 corresponds to the gain curve generation unit. In addition, step S06 corresponds to the smoothing processing unit, steps S07 and S08 correspond to the sound generation data generation unit, and step S09 corresponds to the level de-suppression unit. The limiter unit 26 includes the over-detection unit, absolute value waveform generation unit, peak-holding waveform generation unit, gain curve generation unit, smoothing processing unit, sound generation data generation unit, and level de-suppression unit.

[0054] As described above, according to this embodiment, as shown in Figures 3 and 6, the limiter unit 26 generates sound output data Dsd by multiplying the delayed input waveform Wind and the smooth gain curve Wsgn when the input waveform Win includes an excess portion EX of level Lv.

[0055] Therefore, sound data Dsd is generated based on the input waveform Win. At the same time, by multiplying the delayed input waveform Wind by the smooth gain curve Wsgn, it is possible to limit the amplitude of the waveform Wsd (see Figure 6(c)) represented by the sound data Dsd to below the limiter threshold Th. As the waveform Wsd of the amplitude-limited sound data Dsd is formed smoothly, it is possible to suppress abnormal noises such as harmonic distortion caused by amplitude limitation.

[0056] In particular, the input waveform Win input to the limiter unit 26 is a waveform that has been synthesized in the mixing unit 22 in Figure 1 and its frequency characteristics corrected in the equalizer unit 24, so it is difficult to predict the excess portion EX (see Figure 3(a)) of the level Lv included in the input waveform Win. Even in such cases, the limiter unit 26 of this embodiment can generate sound output data Dsd that suppresses abnormal noises such as harmonic distortion while keeping the amplitude of the waveform Wsd below the limiter threshold Th, as described above.

[0057] Furthermore, in this embodiment, to address the decrease in sound pressure, the time for limiting the amplitude of the waveform Wsd of the sound generation data Dsd, that is, the sum of the gain delay time St, the peak holding time Ht, and the release time Rt, should be set to a value sufficiently smaller than the time corresponding to the human sensitivity to changes in volume, for example, the time constant of the Fast characteristic, which is 125 msec. For example, the sum of the gain delay time St, the peak holding time Ht, and the release time Rt should be set to 20 msec or less. In this case, the amplitude limiting will be short-term, only around the EX portion of the input waveform Win where the level Lv exceeds, thus preventing a perceived decrease in sound pressure, i.e., a decrease in perceptibility.

[0058] The configuration that executes the control processing shown in Figure 2 above makes it possible to provide a sound generation system 8 that combines freedom of simultaneous sound generation, freedom of correction, and suppression of product size and cost, without impairing the recognition of the notification sound.

[0059] Furthermore, according to this embodiment, if the input waveform Win does not include the portion EX that exceeds the level Lv, the limiter unit 26 outputs the sound-producing data Dsd without suppressing the level Lv of the waveform Wsd represented by the sound-producing data Dsd relative to the level Lv of the input waveform Win. Therefore, the amplitude of the waveform Wsd represented by the sound-producing data Dsd is not unnecessarily suppressed.

[0060] (Other embodiments) (1) In the above-described embodiment, the sound system 8 is, for example, a vehicle proximity warning device mounted on an automobile, but this is just one example. The sound system 8 does not have to be a vehicle proximity warning device, and various applications for the sound system 8 can be envisioned. Furthermore, the sound system 8 does not have to be mounted on an automobile.

[0061] (2) In the above embodiment, in step S04 of Figure 2, the limiter unit 26 generates the waveform aggregate 30 of Figure 4 and then generates the peak-holding waveform Wp, but this is just one example. As a result, it is sufficient that the peak-holding waveform Wp has the same waveform shape as the high-level outer shape 301 of the waveform aggregate 30 (see Figure 3(b)), and the limiter unit 26 does not need to generate the waveform aggregate 30.

[0062] (3) In the above-described embodiment, each process performed by the microcontroller 10, such as the processing of each step shown in the flowchart of Figure 2, is implemented by a computer program, but it may also be implemented by hardware.

[0063] (4) The present disclosure is not limited to the embodiments described above and can be implemented in various modified forms. Furthermore, it goes without saying that the elements constituting the embodiments in the above embodiments are not necessarily essential unless explicitly stated to be essential or considered to be essential in principle.

[0064] Furthermore, in the above embodiments, when numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiments are not limited to those specific numbers unless explicitly stated as particularly essential or when they are clearly limited to a specific number in principle. Also, in the above embodiments, when the material, shape, positional relationship, etc. of the components are mentioned, the embodiments are not limited to those material, shape, positional relationship, etc. unless explicitly stated or when they are clearly limited to a specific material, shape, positional relationship, etc. in principle.

Claims

1. A sound generation control device (26) is included in a sound generation system (8) in which a sound generation body (80) produces sound according to a sound generation signal (Ssa) based on sound generation data (Dsd) representing the waveform of sound, and the sound generation control device (26) generates the sound generation data, An over-determination unit (S01, S02) acquires an input waveform (Win) which is the basis of the sound generation data and shows a waveform representing the relationship between the level (Lv) corresponding to the voltage of the sound generation signal and time (Tm), and determines whether the input waveform contains an over-portion (EX) in which the absolute value of the level exceeds a predetermined limiter threshold (Th), If the excess determination unit determines that the input waveform includes the excess portion, the absolute value waveform generation unit (S03) generates an absolute value waveform (Wab) obtained by converting the level in the input waveform to the absolute value of that level, A peak-holding waveform generation unit (S04) generates a peak-holding waveform (Wp) that shows the relationship between the level and the input waveform time (Tm), which is the time in the input waveform, based on the absolute value waveform, A gain curve generation unit (S05) generates a gain curve (Wgn) that shows the relationship between the gain (Gn) obtained based on the level in the peak-holding waveform and the input waveform time, A smoothing processing unit (S06) obtains a smoothed gain curve (Wsgn) based on the gain curve by performing a smoothing process to smooth the gain curve, The system includes a sound generation data generation unit (S07, S08) that generates the sound generation data by multiplying the input waveform with the smooth gain curve a delayed input waveform (Wind) which is shifted by a predetermined waveform delay time (D) to the time-positive side (Dtp) in the time axis direction (Dt) where the input waveform time has elapsed, and the smooth gain curve. The peak-holding waveform is a waveform aggregate (30) composed of the absolute value waveform, a peak-holding section (32) provided at each maximum level point (28) of the absolute value waveform, extending linearly from the maximum level point to the absolute value waveform while showing the same level as the maximum level point for a predetermined peak-holding time (Ht), and a release section (33) provided at each peak-holding section that extends over the peak-holding time, extending from the time-positive end (32a) of the peak-holding section toward the lower level side (DLm) as time progresses toward the lower level side (DLm) until it reaches the absolute value waveform, and the waveform shape obtained by extracting the outer shape (301) formed on the higher level side (DLp) of the waveform aggregate (30). The gain of the gain curve is set to 1 in the time axis range (R1t, R2t) where the level in the peak-holding waveform is less than or equal to the limiter threshold, and in the time axis range (R3t, R4t) where the level in the peak-holding waveform exceeds the limiter threshold, the gain is set to a value obtained from "Gn = Th / Lv", where Gn is the gain, Lv is the level, and Th is the limiter threshold. The smooth gain curve is provided such that, when comparing the peak portions (36a, 37a) where the gain is maximum or minimum with respect to the gain curve, the gain delay time (St) is shifted to the positive side of the time. A sound generation control device wherein the waveform delay time is greater than or equal to the gain delay time, and the peak holding time is greater than or equal to the waveform delay time.

2. The sound control device according to claim 1, further comprising a level non-suppression unit (S09) that outputs the sound data without suppressing the level of the waveform represented by the sound data relative to the level of the input waveform when the excess determination unit determines that the input waveform does not contain the excess portion.

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