JP2005333429A - Voice signal characteristic adjuster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voice signal characteristic adjuster capable of effectively preventing the occurrence of howling in an acoustic space in spite of its simple constitution and simple operation. <P>SOLUTION: The voice signal characteristic adjuster is provided with an input for inputting a voice signal, an output for outputting the voice signal, and a signal processor. The signal processor imparts a gain to the voice signal inputted by the input, and transmits the voice signal to the output after removing a frequency component higher than a cut-off frequency. The gain of the signal processor can be adjusted. The gain and the cut-off frequency are interlocked. The more the gain, the lower the cut-off frequency becomes. By this, the following problem can be solved, namely: (1) an operator conventionally adjusts acoustic equipment in the following manner so as to prevent the occurrence of howling in the acoustic space where microphones and speakers coexist; (2) the gain of an amplifier is increased to a level so that a loud-speaking sound with a sufficient sound volume can be provided to the acoustic space, however, the adjustment of the amplifier and that of a low-pass filter must be simultaneously executed, and therefore, adjustment work is complicated, especially, the adjustment work is difficult for an unskilled person. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an audio signal characteristic adjusting device, and more particularly to an audio signal characteristic adjusting device that can effectively remove howling in an acoustic space.

  In order to prevent listeners from being uncomfortable in various acoustic spaces where microphones and speakers coexist (for example, concert halls and conference halls) and to prevent damage to electroacoustic equipment, It is necessary to prevent howling as much as possible.

  There are usually a plurality of howling frequencies in a certain acoustic space, and the howling margin at each howling frequency is also different. There are many howling frequencies especially in a high frequency band.

  Therefore, in an acoustic space where a microphone and a speaker coexist, an operator of the electroacoustic system adjusts the system as follows.

  Usually, in such an electroacoustic system, an amplifier and a frequency characteristic adjuster are arranged in series between a microphone and a speaker. This amplifier is a type of amplifier whose gain can be arbitrarily set within a predetermined range. The frequency characteristic adjuster here refers to an adjuster that can adjust the amplitude frequency characteristic, such as an equalizer or a low-pass filter. In order to facilitate understanding, here, consider a case where a low-pass filter is used as a frequency characteristic adjuster. This low-pass filter is a type of low-pass filter that can arbitrarily set the cutoff frequency within a predetermined frequency range.

  The operator adjusts the electroacoustic system so that howling does not occur in the acoustic space in which the microphone and the speaker are arranged, and so that a loud sound with a sufficient volume can be provided to the acoustic space. For that purpose, for example, the adjustment is performed in the following procedure.

  First, at the initial stage, the gain of the amplifier is made sufficiently small, and the cutoff frequency of the low-pass filter is set to a sufficiently high frequency. The reason why the cut-off frequency is set to a sufficiently high frequency is to enable audio reproduction with a frequency bandwidth as wide as possible. At this time, howling does not occur because the gain of the amplifier is sufficiently small.

  Next, the gain of the amplifier is gradually increased. When the gain is increased to some extent, howling occurs at the howling frequency (first howling frequency) having the lowest howling margin. The operator then adjusts the low pass filter to lower its cutoff frequency. When the cutoff frequency becomes lower than the howling frequency (first howling frequency), howling disappears.

  If the amplifier gain is still too small to provide a loud sound with sufficient volume in the acoustic space, the amplifier gain is further increased. Then, howling occurs at a howling frequency (second howling frequency) lower than the cutoff frequency of the low-pass filter. The operator adjusts the low pass filter again to lower its cut-off frequency. When the cutoff frequency becomes lower than the howling frequency (second howling frequency), howling disappears.

  In this way, the operator increases the gain of the amplifier while adjusting the cutoff frequency of the low-pass filter. This work continues until the amplifier gain can provide a loud sound of sufficient volume in the acoustic space.

  However, in the above method, adjustment of the amplifier and adjustment of the low-pass filter must be performed simultaneously. For this reason, the adjustment work is complicated, and it is difficult for the unskilled person in particular. In addition, in order to enable the gain adjustment of the amplifier and the frequency characteristic adjustment of the low-pass filter independently, the device circuit may be increased in scale and complexity.

Note that there is an attempt to remove howling using a detection device that detects a howling frequency and a band elimination filter (for example, Patent Document 1), but for that purpose, a device having a complicated configuration is required.
JP-A-11-127296

  An object of the present invention is to provide an audio signal characteristic adjusting apparatus that can effectively prevent howling in an acoustic space despite its simple configuration and simple operation.

  In order to solve the above-described problems, an audio signal characteristic adjusting device according to the present invention includes an input unit that inputs an audio signal, an output unit that outputs an audio signal, and a signal processing unit, and the signal processing unit includes the input unit. The gain is given to the audio signal input by the unit, and the frequency component equal to or higher than the cut-off frequency is removed, and then the audio signal is sent to the output unit to adjust the gain of the signal processing unit. Yes, the gain of the signal processing unit and the cut-off frequency are linked, and the cut-off frequency is lowered as the gain is increased.

  Empirically speaking, in the acoustic space, there are many howling frequencies at relatively high frequencies. If the cut-off frequency is lowered as the gain of the audio signal characteristic adjusting device is increased, howling does not occur even if the gain is increased. Further, when the gain is reduced, it is possible to perform sound expansion in a wide frequency band. Moreover, the operator need only concentrate on gain adjustment. That is, it is not necessary to adjust the filter characteristics separately.

  According to the audio signal characteristic adjusting apparatus of the present application, the apparatus configuration can be simplified and the operation can be simplified. Moreover, howling in the acoustic space can be effectively prevented.

  In the audio signal characteristic adjusting device of the present application, the signal processing unit may have any device configuration. For example, the signal processing unit includes an operational amplifier and a feedback circuit. A variable resistance type resistance unit and a capacitor connected in parallel between the inverting input terminal and the output terminal of the operational amplifier, and by changing the resistance value of the resistance unit, the gain of the signal processing unit Can be configured to change.

  In addition, the resistance portion may be a resistance portion whose resistance value can be changed continuously or stepwise.

  In addition, howling that occurs between the microphone and the speaker when the input unit inputs an output signal of the microphone and is connected to the microphone or the speaker so that the speaker is driven by the audio signal output from the output unit. Can be prevented.

  Further, the microphone and the speaker may be provided in an acoustic space.

  In addition, the audio signal characteristic adjusting device can be incorporated into any type of electroacoustic system for providing a loud sound in an acoustic space. However, the audio signal characteristic adjusting device is incorporated into a conference electroacoustic system. It may be.

  Hereinafter, an audio signal characteristic adjusting apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  First, an electroacoustic system E1 in which an audio signal characteristic adjusting device D is incorporated will be described with reference to FIG.

  This electroacoustic system E1 is installed in a certain acoustic space A1. This acoustic space A1 is an acoustic space in the room, and is a space surrounded by a side wall on the side, a ceiling on the upper side, and a floor surface on the lower side.

  The electroacoustic system E1 is mainly configured by a microphone M, a microphone amplifier 11, an audio signal characteristic adjusting device D, a power amplifier 12, and a speaker S.

  A speaker's voice is input to the microphone M, and an audio signal is output from the microphone M. This audio signal is input to the audio signal characteristic adjusting device D via the microphone amplifier 11. In the audio signal characteristic adjusting device D, gain adjustment and amplitude frequency characteristic adjustment are performed on the audio signal input here. The sound signal adjusted in this way is sent to the power amplifier 12 as an output signal of the sound signal characteristic adjusting device D. The speaker S is driven by the output from the power amplifier 12.

  FIG. 2 is a diagram illustrating an example of a circuit diagram of the audio signal characteristic adjusting device D.

  The audio signal characteristic adjusting device D includes an input terminal (input unit) 25, a resistance element 21, an operational amplifier 23, an output terminal (output unit) 26, and a feedback circuit F. The resistance element 21, the operational amplifier 23, and the feedback circuit F constitute a signal processing unit. The resistance element 21 is interposed between the input terminal 25 and the inverting input terminal of the operational amplifier 23. The operational amplifier 23 and the feedback circuit F are connected in parallel. The non-inverting input terminal of the operational amplifier 23 is connected to the ground, and the output terminal of the operational amplifier 23 is connected to the output terminal (output unit) 26.

  The feedback circuit F is configured by connecting a capacitor 31 and a volume 32 in parallel. The volume 32 functions as a resistance unit that can continuously change its resistance value.

  This audio signal characteristic adjusting device D constitutes a low-pass filter, and its gain and cut-off frequency are adjusted by adjusting the volume 32.

  Here, if the resistance value of the resistance element 21 is R1, the resistance value of the volume 32 is VR1, and the capacitance of the capacitor 31 is C1, the gain (G) and the cut-off frequency (fc) of the audio signal characteristic adjusting device D are Can be represented by the following equation.

G = VR1 / R1
fc = 1 / (2π · C1 · VR1)
From the above equation, it can be seen that when the resistance value of the volume 32 is increased, the gain (G) is increased and the cutoff frequency (fc) is decreased.

  Since the resistance value of the volume 32 can be continuously changed, the gain (G) and the cut-off frequency (fc) can be continuously changed by adjusting the volume 32. Gain and cut-off frequency are linked.

  FIG. 3 is a diagram schematically showing the amplitude frequency characteristic of the audio signal characteristic adjusting device D. As shown in FIG. The amplitude frequency characteristics of the audio signal characteristic adjusting device D when the resistance value of the volume 32 is set to Ra, Rb, and Rc are characteristics indicated by a solid line a, a solid line b, and a solid line c, respectively. Here, there is a relationship of (Ra <Rb <Rc).

  The gain of the amplitude frequency characteristic indicated by the solid line a is Ga, and the cutoff frequency is fca. The gain of the amplitude frequency characteristic indicated by the solid line b is Gb, and the cutoff frequency is fcb. The gain of the amplitude frequency characteristic indicated by the solid line c is Gc, and the cutoff frequency is fcc.

  In the figure, fh1 and fh2 are howling frequencies, respectively.

  Empirically, the howling margin of the howling frequency at a high frequency is small (that is, howling is easy), and the howling margin of the howling frequency at a relatively low frequency is large (that is, it is difficult to perform howling). In the acoustic space A1 of FIG. 1, howling occurs at a frequency fh1 when a gain greater than a predetermined gain that exceeds Ga and does not exceed Gb is set, and exceeds a predetermined gain that exceeds Gb and does not exceed Gc. It is assumed that howling occurs at the frequency fh2 when the gain is set.

  Next, the operation procedure of the audio signal characteristic adjusting device D will be described with reference to FIG.

  First, the operator adjusts the volume 32 so that its resistance value becomes Ra. That is, the audio signal characteristic adjusting device D is adjusted so that the gain of the audio signal characteristic adjusting device D is sufficiently small and the cutoff frequency fc is sufficiently high.

  The howling frequencies fh1 and fh2 are both lower than the cut-off frequency fca. That is, at this time, the howling frequency fh1 and the howling frequency fh2 are included in the reproducible frequency range of the audio signal characteristic adjusting device D. However, howling does not occur because the gain is sufficiently small.

  Next, the operator operates the volume 32 and gradually increases its resistance value. When the resistance value of the volume 32 is Rb, the gain of the audio signal characteristic adjusting device D is Gb, and the cutoff frequency is fcb.

  When the gain Gb is set at the frequency fh1, howling occurs. However, since the signal component having a frequency higher than the cutoff frequency fcb is removed by the audio signal characteristic adjusting device D, howling at the frequency fh1 is performed. Does not occur.

  Further, the operator operates the volume 32 and gradually increases its resistance value. When the resistance value of the volume 32 is Rc, the gain of the audio signal characteristic adjusting device D is Gc, and the cutoff frequency is fcc.

  When the gain Gc is set at the frequency fh2, howling occurs. However, since the signal component having a frequency higher than the cutoff frequency fcc is removed by the audio signal characteristic adjusting device D, howling at the frequency fh2 is performed. Does not occur.

  Since the gain Gc can provide a loud sound with a sufficient volume in the acoustic space A1, the operator stops the operation of the volume 32.

  In this way, the operator can set the audio signal characteristic adjusting device D to a desired gain while simply operating the volume 32 while avoiding the howling frequency.

  In the audio signal characteristic adjusting apparatus D, a mechanical volume can be used as the volume 32, and an electronic volume can also be used.

  The audio signal characteristic adjusting device D has a low-pass filter characteristic, but the amplitude frequency characteristic of the audio signal characteristic adjusting device D does not necessarily have to be a low-pass filter characteristic. For example, an amplitude frequency characteristic such as a band-pass filter having a cutoff frequency of about 20 Hz on the low frequency side and a variable cutoff frequency on the high frequency side may be used.

  Preferred settings for the audio signal characteristic adjusting device D are as follows. That is, when the volume 32 is set to a substantially median value in the resistance value variable range, the loud sound from the speaker S has a volume that can withstand normal use for the use of the acoustic space A1. The electroacoustic system E1 is adjusted. What is necessary is just to determine the capacity | capacitance of the capacitor | condenser 31 of the audio | voice signal characteristic adjustment apparatus D so that howling does not generate | occur | produce in the acoustic space A1, even if the speaker S loudly at such a volume.

  Then, when the speaker utters a voice smaller than normally assumed toward the microphone, the gain of the audio signal characteristic adjusting device D is increased by operating the volume 32. Since the cut-off frequency is lowered as the gain is increased, howling does not occur even if the gain is increased.

  Further, when an output signal of a sound source device that outputs a level higher than that of the microphone amplifier 11, for example, a CD player, is input to the audio signal characteristic adjusting device D, the volume 32 is operated to operate the audio signal characteristic adjusting device D. Reduce gain. Since the level of the input signal to the audio signal characteristic adjusting device D is large, even if the gain of the audio signal characteristic adjusting device D is reduced, a loud sound with a sufficient volume is provided to the acoustic space A1. Further, since the cut-off frequency increases as the gain of the audio signal characteristic adjusting device D decreases, reproduction in a wide frequency band is possible.

  As described above, the audio signal characteristic adjusting device D has a lower cutoff frequency as its gain increases. However, it is not necessary to configure the cut-off frequency to change in conjunction with the gain change in the entire adjustable gain range. The cut-off frequency may be changed in conjunction with the gain change only within a predetermined range of the entire adjustable gain range. For example, in the range not less than the minimum gain that can be set by the audio signal characteristic adjusting device D and not more than the predetermined gain, the cut-off frequency does not change even if the gain is changed, and the gain exceeding the predetermined gain does not change. Only in the range, the cutoff frequency may be lowered as the gain increases.

  This audio signal characteristic adjusting device D can be incorporated into various electroacoustic systems installed in an acoustic space where it is necessary to prevent howling. For example, it can also be incorporated in an electroacoustic system installed in an acoustic space open to the sky such as a baseball field. This is because howling may occur even in an acoustic space partially open to the external space. Of course, it can be incorporated into an electroacoustic system installed in an acoustic space surrounded by walls or the like, such as a gymnasium, or it can be incorporated into an electroacoustic system installed in the internal space of various rooms. .

  FIG. 4 is a schematic configuration diagram showing an example in which the audio signal characteristic adjusting device D is incorporated into the conference electroacoustic system E2 installed in the conference hall (acoustic space) A2.

  The conference electroacoustic system E2 includes a plurality of microphones M for a plurality of participants participating in the conference. The output signals from these microphones M are synthesized by the mixing device 13, and the synthesized audio signal is amplified from the speaker S. The audio signal characteristic adjusting device D is disposed between the mixing device 13 and the speaker S.

  Participant's remarks should be heard by the listener as well as other participants in the conference. Therefore, a relatively loud sound is emitted from the speaker S. For this reason, the loud sound from the speaker S tends to enter the microphone M, which causes howling. Therefore, incorporating the audio signal characteristic adjusting device D into the conference electroacoustic system E2 is effective from the viewpoint of howling prevention.

  Although not shown, a small speaker may be provided for individually providing the synthesized audio signal (the audio signal synthesized by the mixing device 13) to each participant in the conference. Good.

  Next, an audio signal characteristic adjusting device according to another embodiment of the present invention will be described with reference to the drawings.

  FIG. 5 is a diagram showing another example of the circuit diagram of the audio signal characteristic adjusting device D. As shown in FIG.

  The audio signal characteristic adjusting device D includes an input terminal 25, an operational amplifier 23, an output terminal 26, and a feedback circuit F. The input terminal 25 is connected to the non-inverting input terminal of the operational amplifier 23. The operational amplifier 23 and the feedback circuit F are connected in parallel.

  The feedback circuit F is configured by connecting a capacitor 31 and a volume 32 in parallel, and further interposing a resistance element 22 between the inverting input terminal of the operational amplifier 23 and the ground.

  Such an audio signal characteristic adjusting device D can also be used as the audio signal characteristic adjusting device of the electroacoustic system E1 of FIG. 1 or as the audio signal characteristic adjusting device of the electroacoustic system E2 of FIG.

  The audio signal characteristic adjusting device D in FIG. 5 also constitutes a low-pass filter, but by adjusting the volume 32, the gain and the cut-off frequency are adjusted.

  Here, if the resistance value of the resistance element 22 is R2, the resistance value of the volume 32 is VR1, and the capacitance of the capacitor 31 is C1, the gain (G) and the cut-off frequency (fc) of the audio signal characteristic adjusting device D are Can be expressed as:

G = 1 + (VR1 / R2)
fc = 1 / (2π · C1 · VR1)
From the above equation, it can be seen that as the resistance value of the volume 32 is increased, the gain (G) increases and the cut-off frequency (fc) decreases.

  Since the resistance value of the volume 32 can be continuously changed, the gain (G) and the cut-off frequency (fc) in the above equation can also be continuously changed.

  Even when this audio signal characteristic adjusting device D is used, the operator can set the audio signal characteristic adjusting device D to a desired gain while simply operating the volume 32 while avoiding the howling frequency.

  Next, an audio signal characteristic adjusting device according to still another embodiment of the present invention will be described with reference to the drawings.

  FIG. 6 is a diagram illustrating another example of the circuit diagram of the audio signal characteristic adjusting device D.

  The audio signal characteristic adjusting device D includes an input terminal 25, a resistance element 21, an operational amplifier 23, an output terminal 26, and a feedback circuit F. The resistance element 21 is interposed between the input terminal 25 and the inverting input terminal of the operational amplifier 23. The operational amplifier 23 and the feedback circuit F are connected in parallel.

  The feedback circuit F includes a capacitor 31, a plurality of resistance elements 40a to 40f having different resistance values, and a plurality of switching elements 41a to 41f interposed between the resistance elements 40a to 40f and the output terminal of the operational amplifier 23. It is configured.

  Resistor elements 40a to 40f and switch elements 41a to 41f constitute a variable resistance type resistance portion T. The resistance portion T can change its resistance value stepwise depending on which of the plurality of switch elements 41a to 41f is turned on.

  That is, it is possible to select which of the resistance elements 40a to 40f is connected to the output terminal of the operational amplifier 23 by operating the switch elements 41a to 41f. With this selection, the gain of the audio signal characteristic adjusting device D can be selected. A cutoff frequency can be selected. At this time, changes in the gain and the cut-off frequency of the audio signal characteristic adjusting device D are stepwise. Gain and cut-off frequency are linked.

  Also in the audio signal characteristic adjusting device D, the cutoff frequency becomes lower as the gain is increased. The operator can set the audio signal characteristic adjusting device D to a desired gain while avoiding the howling frequency simply by selectively operating the switch elements 41a to 41f.

  Next, an audio signal characteristic adjusting device according to still another embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a diagram showing another example of the circuit diagram of the audio signal characteristic adjusting device D. As shown in FIG.

  The audio signal characteristic adjusting device D includes an input terminal 25, a resistance element 21, an operational amplifier 23, an output terminal 26, and a feedback circuit F. The resistance element 21 is interposed between the input terminal 25 and the inverting input terminal of the operational amplifier 23. The operational amplifier 23 and the feedback circuit F are connected in parallel.

  The feedback circuit F includes a capacitor 31, a volume 32, and a resistance element 22. Both ends of the capacitor 31 are connected to the inverting input terminal and the output terminal of the operational amplifier 23. The moving terminal of the volume 32 is connected to the inverting input terminal of the operational amplifier. One of the fixed terminals of the volume 32 is connected to the output terminal of the operational amplifier 23. The other fixed terminal of the volume 32 is connected to the ground via the resistance element 22.

  Such an audio signal characteristic adjusting device D can also be used as the audio signal characteristic adjusting device of the electroacoustic system E1 of FIG. 1 or as the audio signal characteristic adjusting device of the electroacoustic system E2 of FIG.

  The audio signal characteristic adjusting device D in FIG. 7 also constitutes a low-pass filter, but by adjusting the volume 32, the gain and the cut-off frequency are adjusted.

  Also in the audio signal characteristic adjusting device D, when the resistance value of the volume 32 is increased, the gain is increased and the cut-off frequency is decreased. Further, since the resistance value of the volume 32 can be continuously changed, the gain and the cutoff frequency can also be continuously changed.

  The operator can set the audio signal characteristic adjusting device D to a desired gain while simply operating the volume 32 while avoiding the howling frequency.

  Next, an audio signal characteristic adjusting device D according to still another embodiment of the present invention will be described with reference to the drawings.

  FIG. 8 is a diagram illustrating another example of the circuit diagram of the audio signal characteristic adjusting device D.

  The audio signal characteristic adjusting device D includes an input terminal 25, a resistance element 21, an operational amplifier 23, an output terminal 26, and a feedback circuit F. The resistance element 21 is interposed between the input terminal 25 and the inverting input terminal of the operational amplifier 23. The operational amplifier 23 and the feedback circuit F are connected in parallel.

  The feedback circuit F includes a capacitor 31, a plurality of resistance elements 50a to 50f, 22 connected in series, and a plurality of switch elements 41a to 41f. One end of the resistance elements connected in series is connected to the output terminal of the operational amplifier 23, and the other end is connected to the ground. Each of the switch elements 41 a to 41 f is interposed between a connection point of two adjacent resistance elements among the plurality of resistance elements connected in series and the inverting input terminal of the operational amplifier 23.

  The resistance elements 50a to 50f and the switch elements 41a to 41f constitute a resistance value variable resistance portion T. The resistor T can change the value of the resistor in parallel with the capacitor 31 in a stepwise manner depending on which of the plurality of switch elements 41a to 41f is turned on.

  The operator can select the gain and cut-off frequency of the audio signal characteristic adjusting device D depending on which switch is turned on. At this time, the gain and cut-off frequency of the audio signal characteristic adjusting device D change stepwise.

  Also in the audio signal characteristic adjusting device D, the cutoff frequency becomes lower as the gain is increased. The operator can set the audio signal characteristic adjusting device D to a desired gain while avoiding the howling frequency simply by selectively operating the switch elements 41a to 41f.

  Next, an audio signal characteristic adjusting device D according to still another embodiment of the present invention will be described with reference to the drawings.

  FIG. 9 is a diagram showing another example of the circuit diagram of the audio signal characteristic adjusting device D. As shown in FIG.

  The audio signal characteristic adjusting device D includes an input terminal 25, an A / D converter 60, a gain adjusting unit 61, a low-pass filter unit 62, a D / A converter 63, an output terminal 26, and a control unit 64. And an operation unit 65. The gain adjustment unit 61, the low-pass filter unit 62, the control unit 64, and the operation unit 65 constitute a signal processing unit. The gain adjustment unit 61 and the low-pass filter unit 62 perform signal processing on the digital audio signal. The audio signal input to the input terminal 25 is A / D converted by the A / D converter 60 and then sent to the gain adjusting unit 61. The gain adjusting unit 61 inputs a digital audio signal, gives a gain to the signal, and outputs it. The low-pass filter unit 62 receives the digital audio signal output from the gain adjustment unit 61 and outputs the signal after removing a frequency component equal to or higher than the cutoff frequency from the signal. The signal output from the low-pass filter unit 62 is D / A converted by the D / A converter 63 and then sent to the output terminal 26.

  The operation unit 65 is a member that can be manually operated by an operator, such as a rotary encoder. In response to the signal from the operation unit 65, the control unit 64 controls the gain of the gain adjustment unit 61 and the cutoff frequency of the low-pass filter unit 62. The control unit 64 controls the gain adjustment unit 61 and the low-pass filter unit 62 so that the cutoff frequency of the low-pass filter unit 62 decreases as the gain of the gain adjustment unit 61 increases.

  Also in the audio signal characteristic adjusting device D, the cutoff frequency becomes lower as the gain is increased. The operator can set the audio signal characteristic adjusting device D to a desired gain only by operating the operation unit 65 while avoiding the howling frequency.

  Since the howling can be effectively removed by a simple operation by using the audio signal characteristic adjusting device of the present application, it can be used in the technical field of electroacoustics.

It is a schematic block diagram of the electroacoustic system in which the audio | voice signal characteristic adjustment apparatus according to this invention was integrated. It is a figure which shows an example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus. It is a figure which shows typically the amplitude frequency characteristic of an audio | voice signal characteristic adjustment apparatus. It is a schematic block diagram of the electroacoustic system for meetings in which the audio signal characteristic adjusting device is incorporated. It is a figure which shows the other example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus. It is a figure which shows the other example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus. It is a figure which shows the other example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus. It is a figure which shows the other example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus. It is a figure which shows the other example of the circuit diagram of an audio | voice signal characteristic adjustment apparatus.

Explanation of symbols

A1 Acoustic space A2 Conference hall D Audio signal characteristic adjustment device E1, E2 Electroacoustic system F Feedback circuit M Microphone S Speaker T Resistor 11 Microphone amplifier 12 Power amplifier 13 Mixing device 21, 22 Resistive element 23 Operational amplifier 25 Input terminal 26 Output Terminal 31 Capacitor 32 Volume 40a-40f, 50a-50f Resistive element 41a-41f Switch element 60 A / D converter 61 Gain adjustment part 62 Low pass filter part 63 D / A converter 64 Control part 65 Operation part

Claims (6)

An input unit for inputting an audio signal, an output unit for outputting an audio signal, and a signal processing unit;
The signal processing unit gives a gain to the audio signal input by the input unit and removes a frequency component equal to or higher than a cutoff frequency, and then sends the audio signal to the output unit.
The gain of the signal processor is adjustable;
The gain of the signal processing unit and the cutoff frequency are linked,
An audio signal characteristic adjusting device in which the cut-off frequency decreases as the gain increases. The signal processing unit includes an operational amplifier and a feedback circuit,
The feedback circuit has a resistance value variable type resistance unit and a capacitor connected in parallel between the inverting input terminal and the output terminal of the operational amplifier,
The audio signal characteristic adjusting device according to claim 1, wherein the gain of the signal processing unit is changed by changing a resistance value of the resistance unit.   The audio signal characteristic adjusting device according to claim 2, wherein the resistance portion is a resistance portion whose resistance value can be changed continuously or stepwise. The input unit inputs a microphone output signal,
The audio signal characteristic adjusting apparatus according to any one of claims 1 to 3, wherein the speaker is driven by the audio signal output from the output unit.   The audio signal characteristic adjusting device according to claim 4, wherein the microphone and the speaker are provided in an acoustic space. Built into a conference electroacoustic system,
6. The audio signal characteristic adjusting device according to claim 5, wherein the acoustic space is a conference hall.

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