JP2006262181A - Audio signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an audio signal processor capable of substantially eliminating the distortion of a sound output caused by an excessive input by eliminating a silent state at the time of starting even though an audio signal to be inputted is at any level. <P>SOLUTION: The audio signal processor 10 inputs an audio signal AS inputted to a speaker 3, performs various audio processing of the audio signal and connects the audio signal to the speaker 3. The audio signal processor 10 is provided with an attenuator 20 for reducing the level of the audio signal AS as much as a prescribed attenuation amount and outputting the audio signal and a switch 21 for selectively switching an output from a functional block 15 for performing various audio processing and an output from the attenuator 20 and connecting the output to the speaker 3 side. The switch 21 connects the output of the attenuator 20 to the speaker 3 side by switching control from a control part 11 at the time of starting the processor 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an audio signal processing apparatus, and more particularly to an audio signal processing apparatus that inputs an audio signal to be input to a speaker, performs various audio processing on the audio signal, and connects the audio signal to the speaker.

  A general audio-related device, whether for home use or on-vehicle use, is provided with an audio signal output unit for taking an audio signal from a source such as an AM / FM tuner or a CD player and connecting it to a speaker. For example, when the audio signal output unit is used in a vehicle, a head unit (HU) incorporated in a console panel in front of the front seat in the vehicle interior in order to operate each vehicle-mounted electronic device (including an audio source). ) Is built in. Such a head unit is a genuine product originally mounted on a vehicle together with a speaker. Therefore, the audio signal output from the head unit to the speaker should be set to an appropriate level in advance so that the output is not distorted. It is common.

  A unit for adding various audio processing between the audio signal output unit (HU) and the speaker (in order to obtain a sound quality according to the user's preference for such an existing audio system) (Hereinafter referred to as “audio signal processing device”) may be newly provided. FIG. 4 shows an example of the configuration in that case.

  In the example shown in FIG. 4, the audio signal processing device 30 is based on the detected level, the control unit 31 that controls the entire device, the level detection unit 32 that detects the level of the audio signal output from the HU 2, and the detected level. An attenuator 33 whose attenuation is controlled by the control unit 31, a source selector 34 for selecting the audio source 1 that outputs the audio signal, and various audio processes for the input audio signal based on the control from the control unit 31 And an audio processing unit 35 having a mute function for reducing the level of the audio signal to be output to zero (0) level as necessary, and an output signal of the audio processing unit 35 is amplified to an external speaker. 3 based on control from the control unit 31 and an operation unit 37 having various operation keys. And a display unit 38 for displaying information on the screen.

  As described above, when a speaker is directly connected to a genuine HU (audio signal output unit), the output of the HU is adjusted to an appropriate level in advance so as not to be distorted, but as shown in FIG. When the audio signal processing device 30 is interposed between the two, it is necessary to prevent the output of the device 30 (input of the speaker 3) from being distorted.

  In the prior art, whether or not the input level (HU2 output level) of the audio signal processing device 30 matches the appropriate level is displayed on the screen of the display unit 38, and the audio signal processing is performed while the user confirms this screen. The volume was adjusted appropriately on the HU 2 side so that the output of the device 30 (input of the speaker 3) was not distorted.

As a technique related to the above prior art, for example, as described in Patent Document 1, in a media playback apparatus, an audio signal is selected according to a playback method such as selection of an output signal system, the type of playback media, and the number of playback signal channels There is a technology that performs relative presetting of levels.
Japanese Patent Laid-Open No. 10-284960

  As described above, in the conventional technique (see FIG. 4), when the audio signal processing device 30 is interposed between the speaker 3 and the unit (HU2) that outputs the audio signal to be input to the speaker 3, the output is In order to prevent distortion, level adjustment based on operation (volume adjustment) on the HU 2 side has been performed so that the input level (output level of HU 2) matches an appropriate level.

  However, the audio source that is the target of level adjustment is usually an actual music signal, and the level and frequency characteristics of the signal vary depending on the type of source such as radio or CD, Even for the same source, it differs depending on the type of sound (for example, a difference in genres such as pops, jazz, and classics, a difference in frequency bands such as high, middle, and low frequencies). For this reason, even when the level is adjusted so as to match the appropriate level for an audio signal of an arbitrary source, when the level is changed to another source, the appropriate level is set for the audio signal of the other source. Even if the level is adjusted in this way, there may occur a case where the output distortion cannot be completely absorbed by the attenuator 33 (FIG. 4). That is, when the audio source is changed, the output (input of the speaker 3) may be distorted depending on the case.

  Further, when the audio signal processing device 30 is activated (when the power is turned “ON” or reset is started), an excessive level signal is input to the speaker 3, so that the audio output is distorted due to the excessive input, and in some cases. Inconveniences such as burning of the coil of the speaker 3 may occur.

  For this reason, in the current technology, the audio output to be supplied to the speaker 3 is “muted” until the level adjustment is completed (the audio processing unit 35 in FIG. 4). Therefore, during this period, the output of the speaker 3 is in a “silent state”, and there is a problem that music cannot be listened to.

  The present invention was created in view of the problems of the prior art. When the audio signal is inserted between a unit that outputs an audio signal to be input to a speaker and the speaker, the audio signal is at any level. It is another object of the present invention to provide an audio signal processing apparatus that can eliminate a silent state at the time of startup and can substantially eliminate distortion of sound output due to excessive input.

  In order to solve the above-described problems of the prior art, according to the present invention, in an audio signal processing apparatus that inputs an audio signal to be input to a speaker, performs various audio processing on the audio signal, and connects the audio signal to the speaker. An attenuator for reducing the level of the audio signal by a predetermined amount of attenuation, and an output from the functional block performing the various audio processing and an output of the attenuator are selectively switched and electrically connected to the speaker. An audio signal processing apparatus is provided, comprising: a switch; and a control unit that controls the switch at start-up to switch-connect the output of the attenuator to the speaker.

  According to the audio signal processing device of the present invention, the output of the attenuator (the signal in which the level of the input audio signal is reduced by a predetermined attenuation amount) is connected to the speaker by the switch based on the control from the control unit at the time of activation. As a result, the silent state at the time of activation as seen in the prior art can be eliminated regardless of the level of the input audio signal. Therefore, since the audio signal (level-reduced signal) is output from the speaker during this period, music can be listened to.

  In addition, during this period, the audio signal with a reduced level is input to the speaker, so that it is possible to substantially eliminate the distortion of the audio output caused by the excessive input at the start-up as seen in the prior art. This contributes to prevention of burning of the speaker coil.

  Embodiments of an audio signal processing device according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a configuration when an audio signal processing apparatus according to an embodiment of the present invention is applied to an in-vehicle audio system. The audio signal processing apparatus 10 according to the present embodiment is intended to be used by being inserted between a speaker (audio signal output unit 2) that outputs an audio signal AS to be input to the speaker 3 and the speaker 3. An audio signal output unit 2 (an amplifier 2a provided at the output stage) from an on-vehicle audio source 1 (for example, various sources such as a CD player, an MD player, a DVD player, an AM / FM tuner, a cassette tape deck, etc.) The audio signal AS output via the signal is subjected to various audio processing and output to the speaker 3. The audio signal output unit 2 is built in a head unit (HU) for operating other in-vehicle devices together with the audio source 1, and is incorporated in a console panel in front of the front seat in the vehicle interior.

  As shown in FIG. 1, the audio signal processing apparatus 10 according to the present embodiment includes a control unit 11, a level detection unit 12, a main attenuator 13, a source selector 14, and a microcomputer (microcomputer). An audio processing unit 15, an amplifier 16, an operation unit 17, a display unit 18, a sub attenuator 20, and an amplifier input changeover switch 21 are provided. In addition, although not particularly illustrated, the apparatus 10 is supplied with a power supply voltage from an in-vehicle battery, and a predetermined power supply voltage is appropriately supplied to necessary functional blocks.

  The control unit 11 controls the operation and input / output of each functional block other than the amplifier 16, and as processing related to the present invention, controls the switching of the amplifier input changeover switch 21 as described later, The sub-attenuator 20a (FIG. 3) is controlled to change the amount of attenuation. The control unit 11 is provided with a memory 11a. In the memory 11a, as information relating to the present invention, an analog audio signal (audio signal AS output from the HU 2) to be input to the speaker 3 is stored. A table representing a relationship between a plurality of level values and a plurality of attenuation values set in advance corresponding to each of the plurality of level values is stored. This table is referred to when the attenuation amount of the sub attenuator 20a (FIG. 3) is changed as will be described later.

  The level detector 12 detects the level of the analog audio signal AS output from the HU 2, converts the detected value into a digital signal (A / D conversion), and outputs the digital signal to the controller 11. The main attenuator 13 adjusts the attenuation amount within a predetermined level range for the analog audio signal AS output from the HU 2 based on the control from the control unit 11. That is, the control unit 11 samples the level (digital value) of the audio signal AS detected by the level detection unit 12 for a predetermined time, obtains an average value of peak values during that time, and obtains an appropriate value corresponding to the average value. The attenuator value is calculated, and the main attenuator 13 is set to the attenuator value. The main attenuator 13 reduces the level of the input audio signal AS by the set attenuator value (attenuation amount) and outputs it.

  The audio signal whose level is appropriately reduced through the main attenuator 13 is input to the source selector 14. The source selector 14 is for selecting an audio source 1 (various sources such as a CD player and an AM / FM tuner) that outputs an audio signal AS to be input to the apparatus 10, and this selection is made by the user. This is performed by the control unit 11 based on an input instruction from the operation unit 17. The audio signal selected and output through the source selector 14 is input to the audio processing unit 15.

  The audio processing unit 15 is a functional block for performing various types of audio processing such as volume adjustment and sound quality adjustment on the input audio signal based on the control from the control unit 11, although not particularly illustrated, an A / D converter , An electronic variable resistor (electronic volume), a digital signal processor (DSP), a digital filter, a D / A converter, and the like. For example, the audio signal digitized through the A / D converter is subjected to level adjustment (graphic equalizing adjustment) for each frequency band by the electronic volume based on the control from the control unit 11, and each signal is adjusted by the DSP. Frequency characteristic adjustment (parametric equalizing adjustment) is performed for each frequency band. The digital audio signal that has been equalized and adjusted in this way is converted into an analog audio signal through a digital filter and further through a D / A converter, and then input to the switch 21.

  Although not particularly shown, the operation unit 17 is disposed on the front surface of a housing that accommodates the apparatus 10 and is configured integrally with the display unit 18 in the form of an operation panel. The operation unit 17 is provided with various operation keys necessary for operating the apparatus 10, for example, a switch for turning on / off the power, a key for adjusting the volume, a bus (low Keys for adjusting sound quality such as (sound range) and treble (high range), keys for selecting audio source 1, keys for setting levels, etc., keys for setting / selecting frequency bands, etc. are provided. It has been.

  The display unit 18 is configured by an LCD panel, an organic EL panel, or the like, and the screen displays an operation state of the audio source 1 and various operations input via the operation unit 17 based on control from the control unit 11. Related information, information processed by the control unit 11, and the like are displayed. For example, when a CD is being played, a song title, artist name, track number, performance time, etc. are displayed, and when a radio is being received, a broadcast station name, reception frequency, etc. are displayed. As information related to the present invention, information indicating the level of an audio signal AS (an audio signal that should be input to the speaker 3 originally) detected by the level detection unit 12 is displayed as described later.

  The sub attenuator 20 is one of functional blocks that characterize the present invention, and the level of the analog audio signal AS output from the HU 2 is set to a predetermined attenuation amount based on the control from the control unit 11 as will be described later. The output is reduced. In the present embodiment, this predetermined attenuation amount (attenuation value) is selected to be “−26 dB”. The reason for selecting “−26 dB” is that the amplifier 2 a (corresponding to the amplifier 16 of the apparatus 10) provided in the output stage of the HU 2 (audio signal output unit) connected to the front stage of the apparatus 10 is integrated into an IC. This is because it is a standard product and its gain is often set to 26 dB. Of course, the gain of the amplifier 2a at the output stage may be set to a value other than 26 dB depending on the type or function of the HU 2, and in this case, the attenuation value of the sub attenuator 20 is appropriately set according to the gain value. It is desirable to select.

  The amplifier input change-over switch 21 is one of functional blocks that characterize the present invention together with the sub-attenuator 20, and the output of the sub-attenuator 20 (input audio signal AS is controlled by switching control from the control unit 11 as described later). ) Is selectively switched between an output of the audio processing unit 15 (a signal obtained by performing various audio processes on the audio signal AS) and output. The audio signal selected and output via the amplifier input changeover switch 21 is amplified by the amplifier 16 and then supplied to the external speaker 3 to be output as audio.

  Next, operations related to the present invention performed in the audio signal processing apparatus 10 according to the present embodiment will be described with reference to FIG. FIG. 2 shows a state of amplifier input switching control performed by the control unit 11 in the audio signal processing apparatus 10.

  First, as shown in FIG. 2A, when the apparatus 10 is started up (when the power is turned on or reset is started), the control unit 11 switches the amplifier input changeover switch 21 to the sub-attenuator 20 side. Then, the output of the sub attenuator 20 (a signal obtained by reducing the level of the audio signal AS output from the HU 2 by −26 dB) is input to the amplifier 16. At this time, although the level is reduced, the audio signal AS is output from the speaker 3 through the amplifier 16 as sound.

  Further, the level detection unit 12 detects the level of the audio signal AS, and the detected level (digital value) is monitored by the control unit 11 and is controlled by the display unit 18 based on the control from the control unit 11. Information indicating the level is displayed on the screen. This level detection and display of level information based thereon are continued for a predetermined time by the control unit 11.

  During this period (predetermined time), the user confirms the level information on the screen and operates to prevent distortion of the output of the apparatus 10 (input of the speaker 3), that is, the input audio signal AS. Therefore, volume adjustment (level adjustment) can be performed on the HU 2 side so as to match the appropriate level.

  On the other hand, the control unit 11 performs level detection during this period (predetermined time), obtains an average value of peak values during the period, calculates an appropriate attenuator value corresponding to the average value, and outputs a main attenuator 13. Is set to its attenuator value. In the main attenuator 13, the level of the input audio signal AS is reduced by the set attenuator value (attenuation amount) and output, and the audio signal whose level has been reduced is sent to the audio processing unit 15 via the source selector 14. Entered.

  When a predetermined time has elapsed, as shown in FIG. 2B, the control unit 11 switches and connects the amplifier input changeover switch 21 to the audio processing unit 15 side, and the output of the audio processing unit 15 is amplified. 16 At this time, a signal obtained by performing various audio processes on the audio signal AS whose level is reduced by an appropriate attenuation amount is output as audio from the speaker 3 through the amplifier 16.

  As described above, according to the audio signal processing apparatus 10 according to the present embodiment, when the apparatus 10 is activated, the control unit 11 switches and controls the amplifier input changeover switch 21 to output the sub attenuator 20 (HU2 Is connected to the amplifier 16 (speaker 3), so that the audio signal AS is at any level in the prior art. It is possible to eliminate the mute state at the time of startup. Accordingly, the audio signal AS is output from the speaker 3 during this period (until the level adjustment by the user is completed), so that music can be listened to.

  Further, during this period (predetermined time), the audio signal AS having a reduced level is inputted to the speaker 3, so that the distortion of the audio output due to the excessive input at the start-up as seen in the prior art Can be substantially eliminated. This can also prevent the coil of the speaker 3 from being burned out.

  In the above-described embodiment, when the source 1 of the audio signal AS input to the apparatus 10 is changed, the audio type (for example, genre such as pop, jazz, classic, etc., high frequency, middle frequency, The output of the device 10 (that is, the input of the speaker 3) may be distorted, depending on the frequency band such as a low frequency. For example, when a radio (AM / FM tuner) is selected as the audio source 1, the volume of the audio signal of the radio is adjusted (level adjustment) so as to match the appropriate level, and the source 1 is set to CD. When the player is changed to a player, the signal level (amplitude) of the CD is generally higher than that of the radio. Therefore, even if the volume adjustment (level adjustment) is performed so as to match the appropriate level with respect to the CD audio signal, the output is not necessarily output. In some cases, the sub-attenuator 20 cannot completely absorb the distortion. This is because the attenuation amount of the sub attenuator 20 is fixed to −26 dB.

  Therefore, in order to cope with such inconvenience, it is conceivable to make the attenuation amount of the attenuator variable. FIG. 3 shows an example of the configuration in that case.

  In the configuration example shown in FIG. 3, the sub-attenuator 20a includes four resistors R0, R1, R2, and R3 connected in series, and two NPN transistors Q1 and Q2 connected in series. ing. One end (R0 side) of the resistor string (R0 to R4) is connected to HU2, the other end (R2 side) is connected to the ground, and the connection point between the resistor R0 and the resistor R1 is connected to the switch 21. Yes. The collector of the transistor Q1 is connected to the connection point between the resistors R1 and R2, the emitter of the transistor Q1 (the collector of the transistor Q2) is connected to the connection point between the resistors R2 and R3, and the emitter of the transistor Q2 is connected to the ground. A control signal having a predetermined voltage is applied from the control unit 11 to the bases of the transistors Q1 and Q2.

  In the illustrated example, when the transistors Q1 and Q2 are in the “OFF” state, the attenuation amount of the attenuator 20a is R0 / (R0 + R1 + R2 + R3). When only the transistor Q1 is turned “ON”, both ends of the resistor R2 are short-circuited, so that the attenuation amount of the attenuator 20a is R0 / (R0 + R1 + R3). Similarly, when the transistor Q2 is turned “ON”, both ends of the resistor R3 are short-circuited and the emitter of the transistor Q1 is lowered to the ground level, so that the transistor Q1 is also turned “ON” and both ends of the resistor R2 are also short-circuited. Therefore, the attenuation amount of the attenuator 20a is R0 / (R0 + R1).

  As described above, according to the configuration of the sub-attenuator 20a according to the embodiment of FIG. 3, the amount of attenuation can be changed in three stages according to the predetermined control signal supplied from the control unit 11. At this time, the control unit 11 refers to the table stored in the memory 11a and generates ON / OFF control signals for the transistors Q1 and Q2 according to the level of the audio signal AS detected by the level detection unit 12. .

  As described above, according to the embodiment shown in FIG. 3, even when the source 1 of the audio signal AS input to the apparatus 10 is changed, the HU 2 is adjusted so as to match an appropriate level with respect to the changed source audio signal. When adjusting the volume on the side, select the appropriate attenuation according to the detection level of the audio signal from the multiple attenuations set in the sub-attenuator 20a (in the example shown, 3 levels of attenuation) can do. As a result, it is possible to substantially eliminate distortion of the output of the apparatus 10 (input of the speaker 3).

  In the embodiment shown in FIG. 3, the case where the attenuation amount of the sub-attenuator 20a is changed in three stages has been described as an example. However, the number of stages for making the attenuation amount variable is not limited to three stages.

  In the above-described embodiment, the case where the audio signal processing device according to the present invention is applied to a vehicle is described as an example. However, the present invention is not limited to a vehicle as apparent from the gist thereof. And is widely applicable to general audio-related equipment.

It is a block diagram which shows the structure at the time of applying the audio signal processing apparatus which concerns on one Embodiment of this invention to a vehicle-mounted audio system. It is explanatory drawing of the amplifier input switching control which a control part performs in the apparatus of FIG. It is a circuit diagram which shows the example of 1 structure of the sub attenuator in other embodiment of this invention. It is a block diagram which shows the structure of the audio signal processing apparatus which concerns on an example of a prior art.

Explanation of symbols

1 ... Audio source,
2. Head unit (HU / audio signal output unit),
3 ... Speaker,
10: Audio signal processing device,
11 ... control unit,
11a ... memory,
12 ... Level detector,
13 ... Main attenuator,
14 ... Source selector,
15 ... Audio processing unit (functional block for performing various audio processing),
16 ... Amplifier,
17 ... operation part,
18 ... display part,
20, 20a ... sub-attenuator,
21 ... Amplifier input selector switch,
AS ... Audio signal (to be input to the speaker).

Claims (7)

In an audio signal processing apparatus that inputs an audio signal to be input to a speaker, performs various audio processing on the audio signal, and connects to the speaker.
An attenuator for reducing and outputting the level of the audio signal by a predetermined attenuation amount;
A switch for selectively switching the output from the functional block for performing the various audio processes and the output of the attenuator and electrically connecting to the speaker;
An audio signal processing apparatus comprising: a control unit that controls the switch at the time of start-up to switch and connect the output of the attenuator to the speaker. A level detection unit for detecting the level of the audio signal; and a display unit for providing information through a screen;
The control unit displays information indicating the level of the audio signal detected by the level detection unit on the screen of the display unit when the output of the attenuator is switched and connected to the speaker by controlling the switch. The audio signal processing apparatus according to claim 1, wherein the audio signal processing apparatus is displayed. In place of the attenuator for reducing the level of the audio signal by a predetermined attenuation and outputting it, an attenuator for reducing and outputting the level of the audio signal by a variable attenuation is provided,
The audio signal processing apparatus according to claim 2, wherein the control unit changes the attenuation amount of the attenuator according to the level of the audio signal detected by the level detection unit. A memory storing a table representing a relationship between a plurality of level values of an audio signal to be input to the speaker and a plurality of attenuation values set in advance corresponding to each of the plurality of level values;
The audio signal processing apparatus according to claim 3, wherein the control unit changes an attenuation amount of the attenuator with reference to a table stored in the memory.   The control unit controls the switch to display the information indicating the level of the audio signal detected by the level detection unit on the screen of the display unit for a predetermined time to control the switch from the function block. 4. The audio signal processing apparatus according to claim 2, wherein an output is switched and connected to the speaker.   2. The predetermined attenuation amount in the attenuator is selected in accordance with a gain value of an amplifier provided in an output stage of an audio signal output unit connected to a front stage of the audio signal processing device. The audio signal processing device according to 1.   The audio signal processing apparatus according to claim 1, wherein the audio signal processing apparatus is mounted on a vehicle.

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