Acoustic processing apparatus and acoustic processing program

Abstract

To effectively suppress sound distortion while suppressing the load of signal processing.SOLUTION: An acoustic processing apparatus that controls the dynamic range of an audio signal, includes a division unit that divides a first band signal that does not include low-frequency components and includes at least mid-frequency components from the audio signal, an amplification unit that increases the gain of the first band signal, a setting unit that sets a gain control value for controlling the dynamic range on the basis of the greater signal level of the audio signal level and the amplified signal level obtained by increasing the gain of the first band signal in the amplification unit, and a multiplication unit that multiplies the audio signal by the set gain control value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an audio processing device and an audio processing program. [Background technology]

[0002] A dynamic range compressor (DRC) is known as a signal processing technique for suppressing sound distortion (see, for example, Patent Document 1).

[0003] There are two types of DRC: single-band DRC and multi-band DRC. In single-band DRC, the dynamic range of all frequency bands of an audio signal is compressed uniformly. In multi-band DRC, the dynamic range of multiple frequency bands (e.g. low, mid, high, etc.) is compressed separately. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2022-552456 Summary of the Invention [Problem to be solved by the invention]

[0005] Single-band DRC does not allow for detailed compression control for each frequency band. As a result, single-band DRC may not be able to effectively suppress sound distortion. On the other hand, multi-band DRC allows for detailed compression control for each frequency band. However, multi-band DRC imposes a heavier load on signal processing than single-band DRC.

[0006] In view of the above circumstances, an object of an embodiment of the present disclosure is to provide an audio processing device and an audio processing program that can effectively suppress sound distortion while reducing the load on signal processing. [Means for solving the problem]

[0007] An audio processing device according to one embodiment of the present disclosure is a device that controls the dynamic range of an audio signal, and includes a division unit that divides a first band signal that does not include low-frequency components and includes at least mid-frequency components from the audio signal, an amplification unit that increases the gain of the first band signal, a setting unit that sets a gain control value for controlling the dynamic range based on the greater of the level of the audio signal and the level of the amplified signal obtained by increasing the gain of the first band signal in the amplification unit, and a multiplication unit that multiplies the audio signal by the set gain control value. Effect of the Invention

[0008] According to an embodiment of the present disclosure, there is provided a sound processing device and a sound processing program capable of effectively suppressing sound distortion while reducing the load of signal processing. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of an audio system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a functional block diagram showing audio signal processing by a control unit according to an embodiment of the present disclosure. [Diagram 3] 1 is a diagram relating to filter characteristics of a High Pass filter (HPF) and a Low Pass filter (LPF) according to an embodiment of the present disclosure. [Figure 4A] 1A to 1C are diagrams illustrating amounts of change in frequency characteristics of an audio signal before and after DRC processing in an embodiment of the present disclosure. [Figure 4B] 1A to 1C are diagrams illustrating amounts of change in frequency characteristics of an audio signal before and after DRC processing in an embodiment of the present disclosure. [Figure 4C] 1A to 1C are diagrams illustrating amounts of change in frequency characteristics of an audio signal before and after DRC processing in an embodiment of the present disclosure. [Diagram 5] FIG. 4 is a flowchart showing an acoustic process executed by a control unit in an embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram showing a subroutine of the main DRC process (step S102) in FIG. 5. [Figure 7] FIG. 6 is a diagram showing a subroutine of the sub-DRC process (step S103) in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following description relates to a sound processing device and a sound processing program according to an embodiment of the present disclosure. Note that common or corresponding elements are denoted by the same or similar reference numerals, and duplicate descriptions will be appropriately simplified or omitted.

[0011] 1 is a block diagram showing a configuration of an audio system 1 according to an embodiment of the present disclosure. The audio system 1 is mounted on a vehicle such as a passenger car.

[0012] 1, the audio system 1 includes an audio processing device 2 and a speaker SP. The speaker SP is an in-vehicle speaker installed in the vehicle cabin. In this embodiment, four speakers SP are installed in the vehicle cabin and connected to the audio processing device 2 by wire or wirelessly.

[0013] The number of speakers SP connected to the sound processing device 2 is not limited to four. The sound processing device 2 may be connected to one, two, three, five or more speakers SP.

[0014] The sound processing device 2 is a device that controls the dynamic range of an audio signal, and is an example of a computer that executes a sound processing method and a sound processing program according to an embodiment of the present disclosure. The sound processing device 2 may be an audio device, or may be a device that is a part of a navigation device or an IVI (In-Vehicle Infotainment). The sound processing device 2 is not limited to an in-vehicle device. The sound processing device 2 may be a device in another form, such as a smartphone, a feature phone, a tablet terminal, a PC (Personal Computer), a PDA (Personal Digital Assistant), a PND (Portable Navigation Device), or a portable game machine.

[0015] In an audio listening environment inside a vehicle, sound may become distorted when played at high volume due to, for example, overflow in devices that process audio signals, such as DSPs (Digital Signal Processors), the performance of power amplifiers and speakers, the rigidity of the vehicle body, etc. As a countermeasure against this type of distortion, for example, DRC and dynamic filters (high-pass filters, notch filters, etc.) can be introduced. Sound distortion can be suppressed by using these measures to cut low frequencies, for example.

[0016] In order to improve sound quality and realism, dedicated acoustic tuning may be applied to a vehicle. In this acoustic tuning, for example, a specific frequency band is boosted using an equalizer. This type of acoustic tuning, together with the various factors mentioned above (overflow, various performances, vehicle body rigidity, etc.), affects the acoustic characteristics, so the susceptibility of sound distortion varies depending on the frequency band.

[0017] In order to individually address the susceptibility of sound to distortion in each frequency band, it is preferable to apply a multiband DRC that can individually compress and control the dynamic range for each frequency band. However, multiband DRC imposes a heavy load on signal processing and has a complex configuration. In some cases, it is difficult to apply multiband DRC due to factors such as the performance of the device in which the DRC is embedded and the cost that can be spent on the device.

[0018] Therefore, the sound processing device 2 according to this embodiment is based on single-band DRC and has a configuration that effectively suppresses sound distortion like multi-band DRC.

[0019] Here, with general sound sources (especially pop music, etc.), the recording level of low-frequency components is higher than that of mid- and high-frequency components due to the influence of human hearing characteristics (equal loudness curves). Also, due to the influence of bass drums, bass sounds, and sound reverberation, low-frequency components last longer than mid- and high-frequency components. Also, depending on the DRC level detection method (for example, a method that detects the effective value of a certain section rather than the peak value), the proportion of low-frequency components increases. Due to these factors, sound energy is generally concentrated in the low range.

[0020] DRC tends to respond to low frequencies where sound energy is concentrated. DRC is less responsive to mid-range frequencies where sound energy is less concentrated. Therefore, even if the audio listening environment inside a vehicle is one in which sound is prone to distortion in the mid-range, DRC may not operate properly and sound distortion in the mid-range may not be suppressed.

[0021] Therefore, the sound processing device 2 according to the present embodiment is configured to increase the level of the mid-range components when operating the DRC, thereby improving the operating sensitivity of the DRC for the mid-range. This makes it easier for the DRC to operate properly, for example, for music that is mainly composed of mid-range sounds, in an audio listening environment where sound is likely to be distorted in the mid-range. Therefore, in the sound processing device 2, sound distortion in the mid-range can be effectively suppressed, even though it has a configuration with a light signal processing load based on a single-band DRC.

[0022] As shown in FIG. 1, the sound processing device 2 includes a control unit 10, a player 11, a D / A converter 12, an amplifier 13, a display unit 14, an operation unit 15, and a flash memory 16.

[0023] The sound processing device 2 may have other configurations that are not shown in Fig. 1. That is, the sound processing device 2 has a degree of freedom in its configuration, and various design changes are possible.

[0024] The player 11 is connected to a sound source. The player 11 reproduces an audio signal input from the sound source and outputs the signal to the control unit 10.

[0025] Examples of audio sources include disk media such as CDs (Compact Discs) and SACDs (Super Audio CDs) that store digital audio data, storage media such as HDDs (Hard Disk Drives) and USBs (Universal Serial Buses), smartphones, tablet terminals, and servers that stream data via a network.

[0026] The control unit 10 is configured as, for example, a large scale integration (LSI) and includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a DSP, and the like.

[0027] The control unit 10 executes various programs deployed in a work area of ​​the RAM, thereby controlling the operation of the sound processing device 2.

[0028] The control unit 10 is, for example, a single processor or a multi-processor, and includes at least one processor. When the control unit 10 includes multiple processors, the control unit 10 may be packaged as a single device, or may be configured as multiple devices that are physically separated within the sound processing device 2.

[0029] The control unit 10 processes an audio signal input from a player 11 and outputs the processed signal to a D / A converter 12 .

[0030] The audio signal is converted to an analog signal by the D / A converter 12. This analog signal is amplified by the amplifier 13 and output to each speaker SP. As a result, for example, music recorded in a sound source is reproduced from each speaker SP inside the vehicle.

[0031] The display unit 14 is a device that displays various screens, and includes, for example, a display such as an LCD (Liquid Crystal Display), an organic EL (Electro Luminescence), etc. The display unit 14 may include a touch panel.

[0032] The operation unit 15 includes operators such as mechanical, capacitive non-contact, and membrane switches, buttons, knobs, and wheels. When the display unit 14 includes a touch panel, the touch panel also constitutes a part of the operation unit 15.

[0033] The flash memory 16 stores various programs and various data used by the control unit 10.

[0034] Fig. 2 is a functional block diagram showing audio signal processing by the control unit 10. As shown in Fig. 2, the control unit 10 includes, as functional blocks, a band division unit 110, a main DRC unit 120, a sub DRC unit 130, an addition unit 140, and a multiplication unit 150. Each functional block is realized by an acoustic processing program executed by the control unit 10 working in cooperation with hardware resources.

[0035] The band division unit 110, the main DRC unit 120, the sub-DRC unit 130, the addition unit 140, and the multiplication unit 150 are merely names given by dividing functional blocks of the control unit 10 for convenience. Furthermore, there is a degree of freedom in this division. For example, the addition unit 140 may be included in the sub-DRC unit 130. The multiplication unit 150 may be included in the main DRC unit 120.

[0036] As shown in FIG. 2, the band division unit 110 receives an audio signal S A In the functional block shown in FIG. 2, this audio signal S A is processed to produce an audio signal S A(DRC) The audio signal S A(DRC) The distortion of the sound is suppressed not only in the low range but also in the mid range.

[0037] Specifically, the band dividing section 110 includes an HPF (High Pass filter) 111, an LPF (Low Pass filter) 112, and an addition / subtraction section 113.

[0038] Fig. 3 is a diagram relating to the filter characteristics of the HPF 111 and the LPF 112. In Fig. 3, the vertical axis represents gain (unit: dB) and the horizontal axis represents frequency (unit: Hz).

[0039] In FIG. 3, “All” indicates the audio signal S A The frequency characteristics (amplitude characteristics) when is flat across the entire frequency band are shown.

[0040] As an example of the present disclosure, the low frequency range, the mid frequency range, and the high frequency range are respectively less than 200 Hz, between 200 Hz and less than 10 kHz, and 10 kHz or more. For example, when the audio signal reproduced by the player 11 is a song, the mid frequency range includes sound sources such as vocals and main instruments.

[0041] The HPF 111 and the LPF 112 pass the high-mid range and the low-mid range, respectively. That is, the combination of the HPF 111 and the LPF 112 constitutes a bandpass filter that passes mid-range component signals. The HPF 111 and the LPF 112 have filter orders and stages set so that the frequency characteristics of the passband are flat.

[0042] The audio signal S input to the band division unit 110 A By passing through the HPF 111 and the LPF 112, the audio signal S A The mid-range audio signal S with the low and high frequencies cut (attenuated) from M In FIG. 3, "Mid" is the audio signal S A When the audio signal S has a flat frequency response over the entire frequency range, M The frequency characteristics are shown below.

[0043] In this manner, the band splitting unit 110 splits the audio signal S A From the audio signal S M (an example of a first band signal that does not include low-frequency components and includes at least mid-frequency components).

[0044] It should be noted that any reference to an element using a designation such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations are used for convenience to distinguish between two or more elements. Thus, reference to a first and a second element does not imply, for example, that only two elements are employed, that the first element must precede the second element, etc.

[0045] The adder / subtracter 113 subtracts the audio signal S A Then, the audio signal S input from the LPF 112 M The adder / subtractor 113 subtracts the audio signal S (L&H) In Figure 3, "Low & High" indicates the audio signal S AWhen the audio signal S has a flat frequency response over the entire frequency range, (L&H) The frequency characteristics are shown below.

[0046] Thus, the audio signal S (L&H) The split part is the audio signal S A from audio signal S M It is a signal obtained by dividing the band components excluding (an example of a first band signal) and is an example of a second band signal.

[0047] That is, in this embodiment, the first band signal is a signal of mid-frequency components, and the second band signal is a signal of low-frequency components and high-frequency components.

[0048] Audio signal S (L&H) may be extracted by a filter instead of the addition / subtraction unit 113. That is, in another embodiment, the audio signal S A A filter is used to cut only the mid-frequency components from the audio signal S (L&H) may be extracted.

[0049] The main DRC unit 120 includes level detection units 121 and 122 , a multiplication / division unit 123 , an offset gain unit 124 , a comparison unit 125 , and a single band DRC 126 .

[0050] The main DRC unit 120 receives the audio signal S reproduced by the player 11. A is input, and the mid-frequency component audio signal S M The audio signal S A , S M are input to level detection units 121 and 122, respectively.

[0051] The level detectors 121 and 122 detect the audio signal S A , S M The level of the audio signal S detected by the level detection unit 121 is detected. A The signal level LV AThe audio signal S detected by the level detector 122 is written as M The signal level LV M " is written.

[0052] For example, the level detector 121 detects the audio signal S A By measuring the power, the signal level LV A The level detector 122 detects the level of the audio signal S M By measuring the power, the signal level LV M (Unit: dB).

[0053] Signal level LV A and L.V. M is input to the multiplication / division unit 123. The multiplication / division unit 123 calculates the signal level LV M The signal level LV A Dividing by LV gives the mid-range signal level ratio to the total frequency band. R Calculate the signal level ratio LV R takes a value between 0 and 1 inclusive.

[0054] That is, the main DRC unit 120 including the multiplication / division unit 123 calculates the signal level LV A (An example of the level of an audio signal, the signal level of all frequency components from low to high frequencies) M (which is an example of the level of the first band signal, and is the signal level of the mid-frequency component) ratio.

[0055] Signal level ratio LV R The closer to 1, the greater the audio signal S A In another respect, the signal level ratio LV R The closer to 1, the greater the audio signal S A Therefore, the audio signal S A Therefore, there is little need to cut low-frequency components.

[0056] In contrast, the signal level ratio LVR The closer to 0, the greater the audio signal S A The proportion of low-frequency components is high in the audio signal S. Therefore, sound distortion is likely to occur in the low-frequency range. A Therefore, there is a high need to cut low-frequency components.

[0057] Signal level LV A is input to the comparison unit 125. The signal level LV M is input to the comparison section 125 via the offset gain section 124.

[0058] The offset gain section 124 adjusts the input signal level LV M For example, the offset gain unit 124 increases the gain of the signal level LV M Increase the gain by 3 dB.

[0059] That is, the main DRC section 120 including the offset gain section 124 adjusts the signal level LV M The amplifier operates as an amplifier that increases the gain of the first band signal (in other words, the gain of the first band signal).

[0060] Signal level LV M By increasing the gain of the offset gain unit 124, it is possible to improve the operating sensitivity to the mid-range of the single-band DRC 126, which is less responsive to the mid-range where sound energy is less concentrated.

[0061] The comparator 125 detects the signal level LV input from the level detector 121. A and the signal level LV whose gain has been increased by the offset gain unit 124 M Compare and select the larger signal level LV MAX Output to single band DRC126.

[0062] The single-band DRC 126 detects the signal level LV MAX Based on the audio signal S AGain control value G for controlling the dynamic range of DRC Set.

[0063] Signal level LV MAX When is small, the audio signal S A In any of the low, mid, and high frequency bands, the dynamic range is not so large that the sound is distorted.

[0064] Therefore, the single-band DRC126 is a signal level LV MAX If is less than a predetermined threshold, the gain control value G DRC (an example of a gain control value) is set to 1. In this case, in the final stage of the functional block in FIG. 2, the gain control value G DRC The audio signal is multiplied by 1. In other words, no dynamic range compression is performed by DRC processing.

[0065] In contrast, the signal level LV MAX is large (more precisely, the signal level LV A When the signal level LV is high, the sound is easily distorted, mainly in the low frequency range where there is a lot of energy. MAX is large (more precisely, the signal level LV M is large), this is mainly because the proportion of mid-range frequencies in the song is high and the sound is prone to distortion in the mid-range.

[0066] Therefore, the single-band DRC126 is a signal level LV MAX If is greater than or equal to the predetermined threshold, the gain control value G DRC (an example of a gain control value) is set to a value less than 1. In this case, in the final stage of the functional block in FIG. 2, the gain control value G DRC The audio signal is multiplied by a value less than 1. In other words, the dynamic range is compressed by DRC processing.

[0067] Signal level LV MAXThe higher the signal level, the greater the dynamic range and the more likely the sound will be distorted. MAX The larger the gain control value G DRC Set to a smaller value.

[0068] In this manner, the main DRC section 120 including the single-band DRC 126 controls the signal level LV A (An example of the level of an audio signal, the signal level of all frequency components from low to high frequencies) and signal level LV M (An example of the level of the first band signal, the signal level of the mid-frequency component) is amplified in the amplifier, and the higher signal level LV MAX Based on the audio signal S A The gain control value G for controlling the dynamic range of DRC It operates as a setting unit that sets (an example of a gain control value).

[0069] In addition, the main DRC unit 120 acting as a setting unit sets the signal level LV MAX If is greater than or equal to the predetermined threshold, the gain control value G DRC (An example of a gain control value) is the signal level LV MAX In addition, the main DRC unit 120, which operates as a setting unit, sets the signal level LV MAX If is less than a predetermined threshold, the gain control value G DRC Set to 1.

[0070] The sub-DRC unit 130 includes an adder / subtractor unit 131 , multiplier units 132 , 133 and 134 , and an adder unit 135 .

[0071] The signal level ratio LV calculated by the multiplication / division unit 123 R and the gain control value G set by the single-band DRC126 DRC is input to the sub-DRC unit 130.

[0072] Signal level ratio LV Ris input to the addition / subtraction unit 131. A constant 1 is also input to the addition / subtraction unit 131. The addition / subtraction unit 131 calculates the signal level ratio LV from the constant 1. R (0≦LV R ≦1) is subtracted and the result is output to multiplication unit 134.

[0073] Signal level ratio LV R is also input to the multiplication unit 132. The multiplication unit 132 multiplies this signal level ratio LV R and the audio signal S input from the band division unit 110 (L&H) The multiplication unit 132 multiplies the audio signal S L&H(LVR) " is written.

[0074] Gain control value G DRC is input to the multiplication unit 133. The multiplication unit 133 multiplies the gain control value G DRC and the audio signal S input from the band division unit 110 (L&H) The audio signal output from the multiplication unit 133 is called the "audio signal S L&H(DRC) " is written.

[0075] That is, the multiplication unit 133 multiplies the gain control value G DRC The audio signal S (L&H) By multiplying this, the gain control value G DRC Depending on the audio signal S A The audio signal S with the low and high frequency components suppressed is L&H(DRC) get.

[0076] Generally, sound energy is not concentrated in high frequency components. Therefore, from the viewpoint of suppressing sound distortion, the gain control value G DRC However, if only the low-frequency component is suppressed, the balance between the low-frequency and high-frequency components will be lost. Therefore, in this embodiment, both the low-frequency component and the high-frequency component are suppressed according to the gain control value G DRC is suppressed accordingly.

[0077] The multiplication unit 134 multiplies the input value (constant 1 to signal level ratio LV R ) and the audio signal S L&H(DRC) The multiplication unit 134 multiplies the multiplied audio signal S L&H(DRC) ' to the addition unit 135.

[0078] The adder 135 multiplies the audio signal S L&H(LVR) and the audio signal S input from the multiplication unit 134 L&H(DRC) The adder 135 adds the audio signal S (L&H) ' to the addition unit 140.

[0079] As mentioned above, the signal level ratio LV R The closer to 1, the greater the audio signal S A Therefore, there is less need to cut low-frequency components. R The closer to 1, the greater the audio signal S L&H(LVR) As the proportion of increases, the audio signal S input from the multiplication unit 134 L&H(DRC) In other words, the signal level ratio LV R The closer to 1, the higher the gain control value G DRC The audio signal S is not suppressed according to (L&H) The proportion of increases, and the gain control value G DRC The audio signal S is suppressed according to L&H(DRC) The proportion of

[0080] That is, the signal level ratio LV R The closer to 1, the more likely the audio signal S A DRC processing for the low and high frequencies (here, the gain control value G DRC The effect of the multiplication process is weakened.

[0081] As mentioned above, the signal level ratio LV R The closer to 0, the greater the audio signal S ATherefore, it becomes necessary to cut low-frequency components from the signal level ratio LV R The closer to 0, the greater the audio signal S L&H(LVR) As the proportion of decreases, the audio signal S input from the multiplication unit 134 L&H(DRC) In other words, the signal level ratio LV R The closer to 0, the higher the gain control value G DRC The audio signal S is not suppressed according to (L&H) The proportion of decreases, and the gain control value G DRC The audio signal S is suppressed according to L&H(DRC) The proportion of will be higher.

[0082] That is, the signal level ratio LV R The closer to 0, the more likely the audio signal S A The effect of DRC processing on the low and high frequencies becomes stronger.

[0083] In this way, the sub-DRC unit 130 detects the signal level ratio LV R (An example of the ratio calculated by the calculation unit) and the gain control value G DRC (an example of a gain control value) based on the audio signal S (L&H) It operates as a level control section that controls the level of (an example of a second band signal).

[0084] The adder 140 receives the audio signal S M and the audio signal S input from the adder 140 (L&H) The adder 140 adds the audio signal S A ' to the multiplication unit 150.

[0085] In this way, the adder 140 outputs the level-controlled audio signal S (L&H) and audio signal S M (an example of a first band signal) and a synthesized signal (audio signal S A The signal generator 100 operates as a composite signal generator that generates a composite signal '.

[0086] The multiplication unit 150 multiplies the audio signal S A ' and the gain control value G input from the main DRC unit 120 DRC The multiplication unit 150 multiplies the gain control value G DRC After multiplication, the audio signal S A(DRC) is output to the D / A converter 12.

[0087] In this way, the multiplication unit 150 calculates the gain control value G DRC (An example of the gain control value set in the setting section) is A ' (an example of a composite signal) is multiplied.

[0088] Audio signal S A(DRC) is converted to an analog signal by the D / A converter 12, amplified by the amplifier 13, and output to each speaker SP. As a result, music with reduced distortion in the low and mid ranges is reproduced in the vehicle cabin from each speaker SP.

[0089] 4A to 4C show typical gain control values ​​G DRC and signal level ratio LV R Under the condition, the audio signal S A 1 shows examples of gain or frequency response changes applied to the audio signal S. These examples show the relative amounts of change. A or S A(DRC) 4A to 4C, the vertical axis represents gain (unit: dB), and the horizontal axis represents frequency (unit: Hz).

[0090] FIG. 4A shows the gain control value G DRC is 1 and the signal level ratio LV R 4 shows an example of the change in gain or frequency characteristic when is 0.5.

[0091] G DRC = 1 is the audio signal S AThis shows that the dynamic range is not large in any of the low, mid, or high frequency bands, so sound distortion is unlikely to occur. In this case, the signal level ratio LV R Regardless of the ratio of mid-frequency components to the entire frequency band, the dynamic range is not compressed by DRC. Therefore, the amount of change is 0 dB across the entire frequency band, as shown in FIG. 4A.

[0092] FIG. 4B shows the gain control value G DRC is 0.5 and the signal level ratio LV R The following shows an example of the change in gain or frequency characteristic when is 1.

[0093] In the example of FIG. 4B, substantially only the mid-frequency components are included in the audio signal S A Also, because the dynamic range in the midrange is large, the sound is easily distorted in the midrange. DRC is 0.5 and the signal level ratio LV R Since is 1, the input signal, audio signal S A The audio signal S is a signal with the entire frequency range suppressed by approximately 6 dB. A(DRC) will be output.

[0094] In the example of FIG. 4B, the audio signal S A The gain of the mid-frequency component included in the gain control value G DRC Therefore, even though the sound processing device 2 has a configuration based on a single-band DRC and has a light signal processing load, sound distortion of the mid-range components can be effectively suppressed.

[0095] In the example of Figure 4C, the dynamic range is large in the low and mid ranges, so the sound is easily distorted in the low and mid ranges. DRC is 0.5 and the signal level ratio LV R Since is 0.5, the input signal, audio signal S AThe audio signal S is an audio signal that suppresses the entire frequency range of the A(DRC) will be output.

[0096] In the example of FIG. 4C, sound distortion can be suppressed by appropriately compressing and controlling the dynamic range not only in the mid-range but also in the low-range, where sound energy tends to concentrate.

[0097] FIG. 5 shows a flowchart of the acoustic processing executed by the control unit 10 in this embodiment.

[0098] Note that the order of the steps in the flowcharts shown in the present embodiment may be changed without any inconsistency. For example, although the present disclosure presents the processing of various steps using an exemplary order, the present disclosure is not limited to the order presented.

[0099] Furthermore, the steps of the flowchart shown in this embodiment may be executed in parallel or in parallel to the extent that there is no contradiction. As an example, the main DRC process (step S102) and the sub-DRC process (step S103) may be executed in parallel or in parallel.

[0100] However, the sub-DRC process (step S103) is executed based on the signal level ratio LV obtained in the main DRC process (step S102). R and the gain control value G DRC Immediately after the start of the main DRC process (step S102) and the sub-DRC process (step S103), the signal level ratio LV R and the gain control value G DRC has not been obtained.

[0101] Therefore, the signal level ratio LV R and the gain control value G DRC The initial value (e.g., the signal level ratio LV R , Gain control value G DRC However, the sub-DRC process (step S103) may be performed using either 1).

[0102] As shown in FIG. 5, the control unit 10 receives an audio signal S A is divided (step S101).

[0103] Specifically, the control unit 10 divides the audio signal S input from the player 11 into A The mid-frequency audio signal S M and the low and high frequency audio signal S (L&H) and, divided into.

[0104] The control unit 10 executes the main DRC process (step S102).

[0105] FIG. 6 shows a subroutine of the main DRC process (step S102).

[0106] The control unit 10 converts the audio signal S input from the player 11 into a A The level detector 121 detects the level of the audio signal S input from the band splitter 110. M The level of the signal is detected by the level detector 122 (step S102a).

[0107] The control unit 10 multiplies and divides the signal level LV detected by the level detection unit 122 in the multiplication / division unit 123. M The signal level LV detected by the level detection unit 121 A Divide by this to get the signal level ratio LV R to the sub-DRC unit 130 (step S102b).

[0108] The control unit 10 performs gain offset (step S102c). M The gain of the input signal is increased by the offset gain unit 124.

[0109] The control unit 10 detects the signal level LV Aand the signal level LV whose gain has been increased by the offset gain unit 124 M and are compared in a comparison unit 125 to obtain a signal level LV MAX (Step S102d).

[0110] The control unit 10 compares the signal level LV acquired by the comparison unit 125 with MAX is input to the single-band DRC126 to obtain the gain control value G DRC and outputs it to the sub-DRC unit 130 and the multiplication unit 150 (step S102e).

[0111] The control unit 10 executes the sub-DRC process (step S103).

[0112] FIG. 7 shows a subroutine of the sub-DRC process (step S103).

[0113] The control unit 10 performs a sub-DRC process on the audio signal S input from the band division unit 110. (L&H) The signal level ratio LV R By multiplying the audio signal S L&H(LVR) (Step S103a).

[0114] The control unit 10 performs a sub-DRC process on the audio signal S input from the band division unit 110. (L&H) The gain control value G DRC By multiplying the audio signal S L&H(DRC) The control unit 10 obtains the input value from the addition / subtraction unit 131 (a value obtained by subtracting the signal level ratio LVR from the constant 1) and the audio signal S L&H(DRC) Multiplying and produces an audio signal S L&H(DRC) ' is obtained (step S103b).

[0115] The control unit 10 receives the audio signal S L&H(LVR) and audio signal S L&H(DRC) 'Based on the audio signal S (L&H)' and outputs it to the adding unit 140 (step S103c).

[0116] The control unit 10 adds the audio signal S M and the audio signal S input from the sub DRC unit 130 (L&H) The result is added to the multiplication unit 150 (step S104).

[0117] The control unit 10 multiplies the audio signal S input from the addition unit 140 in the multiplication unit 150. A ', the gain control value G input from the main DRC unit 120 DRC (Step S105).

[0118] The control unit 10 multiplies the audio signal S A(DRC) to the D / A converter 12 (step S106).

[0119] DRC processed audio signal S A(DRC) is output from each speaker SP via the D / A converter 12 and the amplifier 13, so that music with reduced distortion in the low and mid-range is played inside the vehicle cabin.

[0120] The above is a description of exemplary embodiments of the present disclosure. The embodiments of the present disclosure are not limited to those described above, and various modifications are possible within the scope of the technical idea of ​​the present disclosure. For example, the embodiments of the present application also include appropriate combinations of embodiments, etc., which are exemplified in the specification, or obvious embodiments, etc.

[0121] In the above embodiment, the band splitting unit 110 splits the audio signal S A The mid-frequency audio signal S M and the low and high frequency audio signal S (L&H) As a result, in the subsequent functional block, the high-frequency component is divided into the gain control value G DRCTherefore, it is possible to prevent the balance between low and high frequencies from being lost due to DRC processing.

[0122] The embodiment of the present disclosure is not limited to this. A may be divided into an audio signal of mid-high frequency components and an audio signal of low frequency components. In this case, the gain of the mid-high frequency components is increased by the offset gain unit 124 in the main DRC unit 120. Therefore, in this case too, it is possible to improve the operating sensitivity to the mid-frequency range of the single band DRC 126, which is less responsive to the mid-frequency range where sound energy is less concentrated. Therefore, for example, the DRC operates appropriately even for music that is mainly composed of mid-frequency ranges. [Explanation of symbols]

[0123] 1: Sound system 2: Sound processing device 10: Control section 11: Player 12: D / A converter 13: Amplifier 14:Display section 15:Operation section 16: Flash memory 110: Band division section 111:HPF 112:LPF 113: Addition and subtraction section 120: Main DRC section 121: Level detection section 122: Level detection section 123: Multiplication / division section 124: Offset gain section 125: Comparison section 126: Single band DRC 130: Sub DRC section 131: Addition and subtraction section 132: Multiplication section 133: Multiplication section 134: Multiplication section 135: Addition section 140: Addition section 150: Multiplication section

Claims

1. 1. A sound processing device for controlling a dynamic range of an audio signal, comprising: a division unit that divides the audio signal into a first band signal that does not include low-frequency components and includes at least mid-frequency components; an amplifier that increases a gain of the first band signal; a setting unit that sets a gain control value for controlling the dynamic range based on a higher signal level of a level of the audio signal and a level of an amplified signal obtained by increasing the gain of the first band signal by the amplifier unit; a multiplication unit that multiplies the audio signal by the set gain control value; Equipped with Sound processing equipment.

2. The setting unit is If the larger signal level is equal to or greater than a predetermined threshold, the gain control value is set to a value less than 1 in response to the larger signal level; if the greater signal level is less than the predetermined threshold, then set the gain control value to 1; The sound processing device according to claim 1 .

3. a calculation unit that calculates a ratio of a level of the first band signal to a level of the audio signal; a level control unit that controls a level of a second band signal based on the calculated ratio and the gain control value; a composite signal generating unit configured to generate a composite signal of the second band signal and the first band signal, the level of which is controlled; the second band signal is a signal obtained by dividing the audio signal into band components excluding the first band signal by the dividing unit, The multiplication unit multiplies the composite signal by the gain control value. The sound processing device according to claim 1 .

4. the first band signal is a mid-frequency component signal, the second band signal is a signal of the low frequency component and the high frequency component, The high-frequency component is a component having a higher frequency than the mid-frequency component. The sound processing device according to claim 3 .

5. An audio processing program for controlling a dynamic range of an audio signal, comprising: A first band signal is divided from the audio signal, the first band signal including no low-frequency components and at least a mid-frequency component; increasing a gain of the first band signal; setting a gain control value for controlling the dynamic range based on a higher signal level of the level of the audio signal and the level of the amplified signal obtained by increasing the gain of the first band signal; multiplying the audio signal by the set gain control value; The process is executed by a computer. Sound processing program.

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