CN109104672B - Sound noise reduction circuit and microphone - Google Patents
Sound noise reduction circuit and microphone Download PDFInfo
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- CN109104672B CN109104672B CN201810980811.0A CN201810980811A CN109104672B CN 109104672 B CN109104672 B CN 109104672B CN 201810980811 A CN201810980811 A CN 201810980811A CN 109104672 B CN109104672 B CN 109104672B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2410/00—Microphones
- H04R2410/01—Noise reduction using microphones having different directional characteristics
Abstract
The invention relates to the technical field of audio noise reduction, and provides a sound noise reduction circuit and a microphone, wherein the sound noise reduction circuit comprises an input circuit, a gain adjustment circuit and a subtraction circuit which are sequentially and electrically connected; the input circuit comprises a first adding unit and an input amplifying unit, and the first adding unit and the input amplifying unit are both electrically connected with the gain adjusting circuit; the first adding unit is used for receiving the sound signals and adding the sound signals to generate a first audio signal; the input amplification unit is used for receiving the sound signal and amplifying the sound signal to generate a second audio signal; the gain adjusting circuit is used for adjusting the gain to enable the gain of the first audio signal to be equal to the gain of the second audio signal and outputting a first sound adjusting signal and a second sound adjusting signal; the subtracting circuit is used for subtracting the first sound adjusting signal and the second sound adjusting signal and amplifying the first sound adjusting signal and the second sound adjusting signal to obtain a third audio signal subjected to noise reduction. The sound noise reduction circuit and the microphone provided by the invention solve the problem of poor noise reduction effect of a side direction sound source in the prior art.
Description
Technical Field
The invention relates to the technical field of audio noise reduction, in particular to a sound noise reduction circuit and a microphone.
Background
The microphone not only picks up the voice signal but also picks up surrounding environmental noise, and the environmental noise is too large, so that people can receive the voice signal, and the voice is invalid.
In the prior art, a double-microphone technology is generally adopted for sound pickup, and picked double-microphone signals are subtracted in a circuit, so that the scheme has a good noise elimination effect on the front part of a microphone, but for the side direction of the microphone, because the sound wave of a sound source reaches the two microphones, the intensity difference and the phase difference are generated, and the noise elimination effect on the side direction sound source is poor.
Disclosure of Invention
The present invention provides a sound noise reduction circuit and a microphone to solve the problem of poor noise reduction effect.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
the invention provides a sound noise reduction circuit, which is applied to a microphone and used for carrying out noise reduction processing on sound signals, wherein the sound noise reduction circuit comprises an input circuit, a gain adjustment circuit and a subtraction circuit which are sequentially and electrically connected; the input circuit comprises a first adding unit and an input amplifying unit, and the first adding unit and the input amplifying unit are both electrically connected with the gain adjusting circuit; the first adding unit is used for receiving the sound signals and adding the sound signals to generate a first audio signal; the input amplification unit is used for receiving the sound signal and amplifying the sound signal to generate a second audio signal; the gain adjusting circuit is used for adjusting the gain of the second audio signal according to the gain of the first audio signal so as to enable the gain of the first audio signal to be equal to the gain of the second audio signal and outputting a first sound adjusting signal and a second sound adjusting signal; the subtraction circuit is used for subtracting the first sound adjustment signal and the second sound adjustment signal and amplifying the two sound adjustment signals to obtain a third audio signal subjected to noise reduction.
Further, the first adding unit includes a plurality of sub microphones each electrically connected to the first adder, and a first adder electrically connected to the gain adjusting circuit.
Further, the input amplification unit comprises a main microphone and an inverting amplifier, the main microphone and the inverting amplifier are electrically connected, and the inverting amplifier is electrically connected with the gain adjustment circuit.
Furthermore, the plurality of auxiliary microphones are symmetrically distributed along the center of the main microphone, and the plurality of auxiliary microphones and the main microphone are all on the same plane.
Further, the input amplifying unit includes a plurality of main microphones and a second adder, the plurality of main microphones are all electrically connected to the second adder, and the second adder is electrically connected to the gain adjusting circuit.
Furthermore, the plurality of secondary microphones are distributed along the central points of the plurality of main microphones in a central symmetry manner, and the plurality of secondary microphones and the plurality of main microphones are all on the same plane.
Further, the sound noise reduction circuit further includes a band limiting circuit electrically connected to the subtracting circuit, the band limiting circuit configured to limit a passband of the third audio signal within a preset frequency range and output a fourth audio signal.
Further, the sound noise reduction circuit further includes an output circuit, the output circuit is electrically connected to the band limiting circuit, and the output circuit is configured to perform impedance transformation on the fourth audio signal to obtain a noise reduction output signal.
Further, the gain adjusting circuit comprises a voltage dividing circuit, a first voltage follower, a potentiometer and a second voltage follower; the voltage division circuit is electrically connected between the first adding unit and the first voltage follower, the potentiometer is electrically connected between the input amplifying unit and the second voltage follower, and the first voltage follower and the second voltage follower are both electrically connected with the subtraction circuit.
A microphone comprises the sound noise reduction circuit, wherein the sound noise reduction circuit comprises an input circuit, a gain adjustment circuit and a subtraction circuit which are sequentially and electrically connected; the input circuit comprises a first adding unit and an input amplifying unit, and the first adding unit and the input amplifying unit are both electrically connected with the gain adjusting circuit; the first adding unit is used for receiving the sound signals and adding the sound signals to generate a first audio signal; the input amplification unit is used for receiving the sound signal and amplifying the sound signal to generate a second audio signal; the gain adjusting circuit is used for adjusting the gain of the second audio signal according to the gain of the first audio signal so as to enable the gain of the first audio signal to be equal to the gain of the second audio signal and outputting a first sound adjusting signal and a second sound adjusting signal; the subtraction circuit is used for subtracting the first sound adjustment signal and the second sound adjustment signal and amplifying the two sound adjustment signals to obtain a third audio signal subjected to noise reduction.
Compared with the prior art, the invention has the following beneficial effects: the sound noise reduction circuit comprises an input circuit, a gain adjustment circuit and a subtraction circuit which are sequentially and electrically connected, wherein the input circuit comprises a first adding unit and an input amplifying unit, the first adding unit adds received sound signals to generate a first audio signal, and the input amplifying unit amplifies the received sound signals to generate a second audio signal.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 shows a block schematic diagram of an acoustic noise reduction circuit provided by an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of an acoustic noise reduction circuit according to an embodiment of the present invention.
Fig. 3 shows a first structural schematic diagram of an input circuit provided by the embodiment of the invention.
Fig. 4 shows a first position distribution diagram of a main microphone and a sub-microphone provided by an embodiment of the invention.
Fig. 5 shows a second position distribution diagram of the main microphone and the sub-microphone provided by the embodiment of the invention.
Fig. 6 shows a second schematic diagram of an input circuit according to an embodiment of the present invention.
Fig. 7 shows a third position distribution diagram of the main microphone and the sub-microphone provided by the embodiment of the invention.
Fig. 8 is a schematic structural diagram of a gain adjustment circuit according to an embodiment of the present invention.
Fig. 9 shows a schematic diagram of sound source distribution provided by an embodiment of the present invention.
Fig. 10 shows a schematic receiving diagram of sound sources varying along different angles and keeping distances equal according to an embodiment of the present invention.
Fig. 11 shows a vector map of mode 2 provided by an embodiment of the present invention.
Fig. 12 shows a first vector map of mode 3 provided by an embodiment of the present invention.
Fig. 13 shows a second vector map of mode 3 provided by an embodiment of the present invention.
Fig. 14 shows a schematic structural diagram of a microphone provided in an embodiment of the present invention.
Icon: 10-a microphone; 100-a sound noise reduction circuit; 110-an input circuit; 111-a first addition unit; 1111-secondary microphone; 1112-a first adder; 1113-first current limiting resistor; 1114 — a first feedback resistance; 1115 — a first operational amplifier; 112-an input amplification unit; 1121-primary microphone; 1122-inverting amplifier; 1123 — a first resistance; 1124-second resistance; 1125-a second operational amplifier; 1132 — a second adder; 1133 — a second current limiting resistor; 1134 — a second feedback resistance; 1135 — a third operational amplifier; 120-a gain adjustment circuit; 121-a voltage divider circuit; 1211 — a first dividing resistor; 1212-second voltage dividing resistor; 122 — first voltage follower; 123-a potentiometer; 124-a second voltage follower; 130-a subtraction circuit; 131-a third resistor; 132-a fourth resistance; 133-fifth resistance; 134-sixth resistance; 135-a fourth operational amplifier; 140-band limiting circuit; 141-a first capacitance; 142-a seventh resistance; 143-a fifth operational amplifier; 144-eighth resistance; 145-a second capacitance; 150-output circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
First embodiment
Referring to fig. 1, an embodiment of the present invention provides an acoustic noise reduction circuit 100, where the acoustic noise reduction circuit 100 is applied to a microphone 10 and is used for performing noise reduction processing on an acoustic signal, the acoustic noise reduction circuit 100 includes an input circuit 110, a gain adjustment circuit 120, a subtraction circuit 130, a band limiting circuit 140, and an output circuit 150, and the input circuit 110, the gain adjustment circuit 120, the subtraction circuit 130, the band limiting circuit 140, and the output circuit 150 are electrically connected in sequence.
Referring to fig. 2 and fig. 3, the input circuit 110 includes a first adding unit 111 and an input amplifying unit 112, and both the first adding unit 111 and the input amplifying unit 112 are electrically connected to the gain adjusting circuit 120.
In an embodiment of the present invention, the first adding unit 111 is configured to receive sound signals and add them to generate a first audio signal. The first adding unit 111 includes a first adder 1112 and a plurality of sub-microphones 1111, each of the plurality of sub-microphones 1111 is electrically connected to the first adder 1112, the first adder 1112 is electrically connected to the gain adjusting circuit 120, and the sub-microphones 1111 may be, but not limited to, a moving coil microphone, an aluminum ribbon microphone, a condenser microphone, and an electret microphone. A plurality of sub microphones 1111 are electrically connected to the first adder 1112, and each sub microphone 1111 is configured to convert a received sound signal into an electrical signal and transmit the electrical signal to the first adder 1112. The first adder 1112 includes a plurality of first current limiting resistors 1113, a first feedback resistor 1114, and a first operational amplifier 1115 electrically connected to the plurality of sub-microphones 1111 in a one-to-one correspondence, wherein the first operational amplifier 1115 includes a first non-inverting input terminal, a first inverting input terminal, and a first output terminal. Each of the first current limiting resistors 1113 is electrically connected between the sub-microphone 1111 and the first inverting input terminal of the first operational amplifier 1115, the first non-inverting input terminal of the first operational amplifier 1115 is grounded, the first feedback resistor 1114 is electrically connected between the first inverting input terminal and the first output terminal of the first operational amplifier 1115, and the resistance value (e.g., 10K Ω) of each of the first current limiting resistors 1113 is equal to the resistance value (e.g., 10K Ω) of the first feedback resistor 1114. The sound signal is passed through a first addition unit 111 to generate a first audio signal.
In the embodiment of the present invention, the input amplifying unit 112 is configured to receive the sound signal and amplify the sound signal to generate the second audio signal. The input amplifying unit 112 includes a main microphone 1121 and an inverting amplifier 1122, the main microphone 1121 is electrically connected to the inverting amplifier 1122, and the inverting amplifier 1122 is electrically connected to the gain adjusting circuit 120. The primary microphone 1121 may be, but is not limited to, a moving coil microphone, an aluminum ribbon microphone, a condenser microphone, and an electret microphone. The inverting amplifier 1122 includes a first resistor 1123, a second resistor 1124, and a second operational amplifier 1125. The second operational amplifier 1125 includes a second non-inverting input terminal, a second inverting input terminal, and a second output terminal. Optionally, the first resistor 1123 is electrically connected between the main microphone 1121 and the second inverting input terminal of the second operational amplifier 1125, the second resistor 1124 is electrically connected between the second inverting input terminal and the second output terminal of the second operational amplifier 1125, the second inverting input terminal of the second operational amplifier 1125 is grounded, and the second output terminal of the second operational amplifier 1125 is electrically connected to the gain adjustment circuit 120. The sound signal passes through the input amplification unit 112 to generate a second audio signal and is output through a second output terminal.
It should be noted that the amplification factor of the inverting amplifier 1122 is related to the resistance value of the first resistor 1123 and the resistance value of the second resistor 1124, and the amplification factor of the inverting amplifier 1122 is related to the total number of the sub-microphones 1111 and the total number of the main microphones 1121, and the relationship therebetween is: the amplification factor is equal to the second resistance/the first resistance is equal to the total number of the auxiliary microphones/the total number of the main microphones. For example, 2 sub microphones and 1 main microphone are provided in the input circuit 110, and then the amplification factor is 2 in the second resistor/first resistor 2/1, that is, the amplification factor is 2, and the resistance value of the second resistor 1124 needs to be set to 2 times that of the first resistor 1123.
It should be noted that the plurality of sub microphones 1111 and the main microphone 1121 are all in the same plane, and the distances from the plurality of sub microphones 1111 to the main microphone 1121 are equal. Referring to fig. 4, when there are 2 sub-microphones 1111 and 1 main microphone 1121, the distances from the 2 sub-microphones 1111 to the main microphone 1121 are equal, and the 2 sub-microphones 1111 and the main microphone 1121 are on the same straight line; referring to fig. 5, when the number of the sub-microphones 1111 is greater than 2, every 2 sub-microphones 1111 are symmetrically distributed along the center of the main microphone 1121, and all the sub-microphones 1111 and the main microphone 1121 are on the same plane.
In another embodiment of the present invention, referring to fig. 6, the input amplifying unit 112 includes a second adder 1132 and a plurality of main microphones 1121, each of the main microphones 1121 is electrically connected to the second adder 1132, and each of the main microphones 1121 is configured to convert a received sound signal into an electrical signal and send the electrical signal to the second adder 1132. Optionally, the second adder 1132 includes a plurality of second current limiting resistors 1133, a second feedback resistor 1134, and a third operational amplifier 1135 electrically connected to the plurality of main microphones 1121 in a one-to-one correspondence, and the third operational amplifier 1135 includes a third non-inverting input terminal, a third inverting input terminal, and a third output terminal. Each of the second current limiting resistors 1133 is electrically connected between one of the main microphones 1121 and the third inverting output terminal of the third operational amplifier 1135, the third non-inverting input terminal of the third operational amplifier 1135 is grounded, the second feedback resistor 1134 is electrically connected between the third inverting input terminal and the third output terminal of the third operational amplifier 1135, and the third output terminal of the third operational amplifier 1135 is electrically connected to the gain adjusting circuit 120. The sound signal passes through the input amplification unit 112 to generate a second audio signal and is output through a second output terminal.
It should be noted that the first adder 1112 and the second adder 1132 are not limited to the adder circuits described in the embodiments of the present invention, and only a circuit capable of adding two signals and outputting a signal may be implemented, and the circuit form is not limited to the above-described circuit form.
It should be noted that the plurality of sub microphones 1111 are distributed along the central point of the plurality of main microphones 1121 in a central symmetry manner, and the plurality of sub microphones 1111 and the plurality of main microphones 1121 are all on the same plane. Referring to fig. 7, when there are 4 sub-microphones 1111 and 4 main microphones 1121, the 4 main microphones 1121 and 4 sub-microphones 1111 are all on the same plane, and the 4 sub-microphones are distributed along the center points of the 4 main microphones in a central symmetry manner.
In the embodiment of the present invention, the gain adjustment circuit 120 is provided due to the inconsistency of the sensitivity of the microphones and the errors of the circuit elements. The gain adjusting circuit 120 is electrically connected between the input circuit 110 and the subtracting circuit 130, and is configured to adjust the gain of the second audio signal according to the gain of the first audio signal so that the gain of the first audio signal is equal to the gain of the second audio signal, and output a first sound adjusting signal and a second sound adjusting signal. Referring to fig. 8, the gain adjustment circuit 120 includes a voltage divider 121, a first voltage follower 122, a potentiometer 123 and a second voltage follower 124, the voltage divider 121 is electrically connected between the first adding unit 111 and the first voltage follower 122, the potentiometer 123 is electrically connected between the input amplifying unit 112 and the second voltage follower 124, and both the first voltage follower 122 and the second voltage follower 124 are electrically connected to the subtracting circuit 130. The voltage dividing circuit 121 is configured to divide the first audio signal to determine a gain of the first audio signal, the voltage dividing circuit 121 includes a first voltage dividing resistor 1211 and a second voltage dividing resistor 1212, one end of the first voltage dividing resistor 1211 is electrically connected to the first output terminal of the first adding unit 111, the other end of the first voltage dividing resistor 1211 is electrically connected to one end of the second voltage dividing resistor 1212, and the other end of the second voltage dividing resistor 1212 is grounded; the first voltage follower 122 is electrically connected between the voltage divider circuit 121 and the subtraction circuit 130, optionally, the first voltage follower 122 includes a fourth non-inverting input terminal, a fourth inverting input terminal, and a fourth output terminal, and the fourth output terminal of the first voltage follower 122 outputs the first audio adjustment signal. The first audio signal passes through the voltage divider circuit 121 and the first voltage follower 122 to obtain a first audio adjustment signal. The potentiometer 123 is used for adjusting the voltage of the second audio signal, the potentiometer 123 includes a first fixed end, a second fixed end and an adjustable end, the first fixed end is electrically connected with the second output end, the second fixed end is grounded, the adjustable end is connected with the second voltage follower 124, and the movement of the adjustable end can change the voltage of the second audio signal to adjust the gain of the second audio signal, so that the gain of the second audio signal is equal to the gain of the first audio signal. The second voltage follower 124 is electrically connected between the potentiometer 123 and the subtraction circuit 130, and optionally, the second voltage follower 124 includes a fifth non-inverting input terminal, a fifth inverting input terminal, and a fifth output terminal, where the fifth output terminal outputs a second audio adjustment signal, and the second audio adjustment signal is obtained by the second audio signal passing through the potentiometer 123 and the second voltage follower 124.
In other embodiments of the present invention, the positions of the voltage divider 121 and the potentiometer 123 may be changed, and the gain of the first audio signal may also be adjusted according to the gain of the second audio signal, so that the gain of the first audio signal is equal to the gain of the second audio signal.
In the embodiment of the present invention, the subtracting circuit 130 is electrically connected between the gain adjusting circuit 120 and the band limiting circuit 140, and the subtracting circuit 130 is configured to subtract the first sound adjusting signal and the second sound adjusting signal and amplify the subtracted signals to obtain a third audio signal after noise reduction. The subtracting circuit 130 includes a third resistor 131, a fourth resistor 132, a fifth resistor 133, a sixth resistor 134 and a fourth operational amplifier 135, wherein the fourth operational amplifier 135 includes a sixth non-inverting input terminal, a sixth inverting input terminal and a sixth output terminal, one end of the third resistor 131 is electrically connected to the fourth output terminal of the first voltage follower 122, the other end of the third resistor 131 is electrically connected to the non-inverting input terminal of the fourth operational amplifier 135, one end of the fourth resistor 132 is electrically connected to the non-inverting input terminal of the fourth operational amplifier 135, the other end of the fourth resistor 132 is grounded, one end of the fifth resistor 133 is electrically connected to the fifth output terminal of the second voltage follower 124, the other end of the fifth resistor 133 is electrically connected to the sixth inverting input terminal of the fourth operational amplifier 135, one end of the sixth resistor 134 is electrically connected to the sixth inverting input terminal of the fourth operational amplifier 135, and the other end of the sixth resistor 134 is electrically connected to the sixth output terminal of the fourth operational amplifier 135. The first audio adjustment signal and the second audio adjustment signal pass through the subtraction circuit 130 to obtain a third audio signal.
It should be noted that the resistances of the third resistor 131, the fourth resistor 132, the fifth resistor 133 and the sixth resistor 134 are required to satisfy the fourth resistor/the third resistor, the sixth resistor/the fifth resistor, and the third audio signal, the fourth resistor/the third resistor x (the first audio adjusting signal — the second audio adjusting signal).
The subtracting circuit is not limited to the subtracting circuit described in the embodiment of the present invention, and only a circuit that subtracts two signals and outputs a signal may be implemented, and the circuit is not limited to the above circuit form.
In the following, 2 sub microphones and 1 main microphone are taken as an example for reasoning.
Referring to fig. 9, for convenience of description, the two sub microphones are respectively A, C, and the main microphone is B. The two secondary microphones A, C are equidistant from the primary microphone B, and the three microphones are in a straight line, S1 is a far sound source, and S2 is a near sound source. When the near sound source S2 is closer to the primary microphone, the primary microphone B receives a sound wave with a much greater intensity than the secondary microphone A, C and a phase leading the primary microphone A, C because the sound intensity is inversely proportional to the distance from the sound source. There is still a large output when the sound signal received by the primary microphone B is multiplied by twice and subtracted by the sum of the two secondary microphones A, C. When the distant sound source S1 is far from the main microphone B, the sound signal relationship is intensity a > B > C and phase a > B > C because of the distance S1A < S1B < S1C, where > indicates an advance. Since the sound signal received by the main microphone B in the sound noise reduction circuit 100 is multiplied by twice and then the sum of the two sub-microphones A, C is subtracted, the phase of one of the 2 sub-microphones A, C is leading the main microphone B and the other is smaller than the lagging main microphone B, so that the sum of the 2 sub-microphones A, C is close to the main microphone B, and this effect is more significant as the distance from the sound source to the sub-microphone A, C and the main microphone B is longer. The output is therefore small, i.e., the sound receiving capacity for the remote sound source S1 is small. For the phase relationship, the sub-microphone a receives the sound signal with a phase leading the main microphone B and the sub-microphone C receives the sound signal with a phase lagging the main microphone B, and the phases of the sub-microphone a and the sub-microphone C are added to obtain an average value. This value is very close to the phase value of the primary microphone B. Therefore, when the sound signal received by the main microphone B is multiplied by 2 times minus the sub microphone a and the sub microphone C, no output is made because the phase difference is small (assuming that the intensities are equal, the foregoing indicates that the intensity difference is small). This effect is more pronounced as the original sound source S1 is farther from the primary microphone B and the secondary microphone A, C. Therefore, the sound noise reduction circuit 100 has a small sound wave receiving capability to the distant sound source S1 in terms of phase, thereby improving the noise reduction effect to the distant sound source.
Theoretical calculations of noise immunity are performed below.
Referring to fig. 10, A, B, C can be considered as 3 sound source receiving points. AB. Distances between BC are all 2cm, a circle is drawn at a distance of 20cm from a B receiving point to show that the distance from a sound source S to the B receiving point is 20cm, and an output value of B, an output value of B-A (the same as an output value of A-B and the opposite phase of A-B) and a value of B- (A + C)/2 are calculated to obtain comparison of anti-noise effects. Where the output of B is received by one main microphone, i.e. mode 1, B-a is output by one sub microphone and one main microphone in a different manner, i.e. mode 2, and B- (a + C)/2 is the receiving scheme of two sub microphones and one main microphone in the embodiment of the present invention, i.e. mode 3. A, B, C all receive the signal when the sound source S sends out the signal, the output voltage signal amplitude is proportional to the sound pressure. Let the output of B be reference ratio 1 and the signal phase be 0. Since the sound pressure is inversely proportional to the distance, the output of B (i.e., the sound pressure at point B) is set to UBZ/SB, where Z is a constant related to temperature, elastic modulus of air, density, temperature, etc. U shapeA＝Z/SA，UCZ/SC, then UA/UB＝(Z/SA)/(Z/SB)＝SB/SA，UA＝(SB/SA)*UBDue to the arrangement of UBIs 1, then UAU for SB/SACSB/SC. The angle between the horizontal line connecting the sound source S and the sound source B is 30 DEG, and U is calculatedB，UA-UB，UB-(UA+UC) And/2, a comparison of the results is obtained. Then, the same method was used to calculate 0 °, 15 °, 45 °, 60 °, 75 °, and 90 °, and the output changes at the respective angles were obtained.
Referring to fig. 11 and fig. 12 in combination, as SB is 20, BA is 2, and the angle α between SB and the horizontal is 30 °, then the angle SBA is 60 °. From the cosine theorem, known SA2＝SB2+AB2-2 × SB × COS (60 °), substituting SB ═ 20 and AB ═ 2, yielding SA ═ 19.07878. By UASubstituting for SB/SA to obtain UA20/19.07878-1.04828. Due to SA<SB, and hence the arrival time of the source signal S at A is advanced relative to B by an amount related to the difference between SA and SB and the signal frequency. Assuming that the signal frequency is 1KHz and the sound speed is 340m/s, the signal wavelength λ is 0.34m and 34cm, C/f is 340/1000. The ratio of the distance difference between SA and SB to 34cm is UAThe phase value of the lead. This gave ((SB-SA)/34) × 360 ° ((20-19.07878)/34) × 360 ° (+ 9.75409 °). To obtain UAThe signal of (3) is 1.04828 & lt +9.75409 DEG, and SC & lt 21.0713 is obtained by applying the cosine theorem again to obtain UCSB/SC 20/21.07131 0.94916 with a phase of-11.34326 °. Thus obtaining UC0.94916 < 11.34326 deg. The output from mode 2 is UA-UBDrawing vector diagram, known as UALength 1.04828, UBIs 1, UAAnd UBThe included angle is 9.75409 degrees, and U is obtained by the cosine lawA-UB0.18066. Since it is only necessary to obtain the amplitude of the output, U is not calculatedA-UBThe phase angle of (c). Referring to FIG. 13, mode 3 is to subtract half of the sum of A and C from the output of B, so we first calculate the sum output of A and C. Drawing vector diagram, solving U by cosine theoremA+UCThe value of (b) is 1.96377-0.26512 degrees. Finally, calculate UB-(UA+UC) A result of 0.01864 was obtained,/2. Only amplitude is required and phase angle is not calculated. After the above values are obtained, the ability to attenuate distant source signals is summarized. Output U in mode 1BFor the reference, the suppression ratios were obtained by dividing the output of the method 2 and the output of the method 3, respectively, and were 5.53 and 53.64, respectively. The result obtained was 1/5.5 of the case where the caseMode 3 is 1/53.64 in mode 1. The suppression capability of the mode 3 for a distant sound source is larger than that of the mode 2, and is close to 10 times in a state of being 30 degrees and 20cm distant. In the same way, data analogies for other angles are obtained, see table 1 below. It can be seen that the suppression capabilities of both mode 2 and mode 3 begin to decrease as the angular offset increases, but mode 3 is significantly better than mode 2, about 5-10 times the suppression capability of mode 2, and 14-60 times the suppression capability of mode 1, improving the side direction sound source noise cancellation effect.
Table 1 parameter table for different receiving angles
In the embodiment of the present invention, the band limiting circuit 140 is electrically connected between the subtracting circuit 130 and the output circuit 150, and is configured to limit the passband of the third audio signal within the preset frequency range and output the fourth audio signal. The band limiting circuit 140 may be a band pass filter for filtering out high frequency components and low frequency components of the third audio signal outside a preset frequency, and optionally, the preset frequency range may be 100Hz to 5000 Hz. For example, the band limiting circuit 140 includes a first capacitor 141, a seventh resistor 142, a fifth operational amplifier 143, an eighth resistor 144, and a second capacitor 145, the fifth operational amplifier 143 includes an eighth non-inverting input terminal, an eighth inverting input terminal, and an eighth output terminal, one end of the first capacitor 141 is connected to the sixth output terminal, the other end of the first capacitor 141 is connected to the eighth non-inverting input terminal of the fifth operational amplifier 143, one end of the seventh resistor 142 is connected to the eighth non-inverting input terminal of the fifth operational amplifier 143, and the other end of the seventh resistor 142 is grounded. The circuit formed by the first capacitor 141 and the seventh resistor 142 is used for filtering low-frequency components, that is, in the embodiment, a signal lower than 100Hz in the third audio signal, an eighth inverting input terminal of the fifth operational amplifier 143 is electrically connected to an eighth output terminal, one end of the eighth resistor 144 is electrically connected to the eighth output terminal of the fifth operational amplifier 143, the other end of the eighth resistor 144 is electrically connected to the output circuit 150, the other end of the eighth resistor 144 is also electrically connected to one end of the second capacitor 145, and the other end of the second capacitor 145 is grounded. The circuit formed by the eighth resistor 144 and the second capacitor 145 is used to filter out high frequency components, that is, signals higher than 5000Hz in the third audio signal in this embodiment, and the fourth audio signal is obtained through the band limiting circuit 140.
In the embodiment of the present invention, the output circuit 150 is electrically connected to the band limiting circuit 140, and is configured to perform impedance transformation on the four audio signals. The output circuit 150 includes a third voltage follower, the third voltage follower includes an eighth non-inverting input terminal, an eighth inverting input terminal, and an eighth output terminal, the eighth non-inverting input terminal of the third voltage follower is electrically connected to the band limiting circuit 140, the eighth inverting input terminal of the third voltage follower is electrically connected to the eighth output terminal, and the third voltage follower performs impedance transformation on the fourth audio signal to obtain the noise reduction output signal.
The working principle provided by the embodiment of the invention is as follows: in the sound noise reduction circuit 100, the input circuit 110 includes a first adding unit 111 and an input amplifying unit 112, the first adding unit 111 is used for receiving sound signals and adding to generate a first audio signal; the input amplifying unit 112 is used for receiving the sound signal and amplifying the sound signal to generate a second audio signal; the gain adjustment circuit 120 is configured to adjust the gain of the second audio signal according to the gain of the first audio signal so that the gain of the first audio signal is equal to the gain of the second audio signal, and output a first sound adjustment signal and a second sound adjustment signal; the subtraction circuit 130 is configured to subtract the first sound adjustment signal from the second sound adjustment signal and amplify the subtracted signal to obtain a noise-reduced third audio signal, and the band limiting circuit 140 is configured to limit a passband of the third audio signal within a preset frequency range and output a fourth audio signal; the output circuit 150 is configured to perform impedance transformation on the fourth audio signal to obtain a noise reduction output signal.
Second embodiment
Referring to fig. 14, a microphone 10 according to an embodiment of the present invention includes the acoustic noise reduction circuit 100 according to the first embodiment of the present invention, and the acoustic noise reduction circuit 100 may be disposed inside the microphone 10 for acoustic noise reduction.
In summary, the input circuit includes a first adding unit and an input amplifying unit, the first adding unit adds the sound signals received by the first sensors to generate a first audio signal, the input amplifying unit amplifies the received sound signals to generate a second audio signal, and the gain adjusting circuit is configured to adjust the gain to make the gain of the first audio signal equal to the gain of the second audio signal and output a first sound adjusting signal and a second sound adjusting signal; the subtraction circuit is used for subtracting the first sound adjusting signal and the second sound adjusting signal and amplifying the subtracted signals to obtain a third audio signal subjected to noise reduction, so that the noise reduction effect of the sound source in the opposite side direction is improved, and the noise reduction effect of the sound source in a far distance can also be improved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
Claims (8)
1. A kind of sound noise reduction circuit, characterized by, apply to the microphone, is used for carrying on the noise reduction processing to the voice signal, the said sound noise reduction circuit includes input circuit, gain adjustment circuit and subtraction circuit that connect electrically sequentially;
the input circuit comprises a first adding unit and an input amplifying unit, and the first adding unit and the input amplifying unit are both electrically connected with the gain adjusting circuit; the first adding unit comprises a plurality of auxiliary microphones and a first adder, and the auxiliary microphones are all electrically connected with the first adder; the input amplifying unit comprises a main microphone and an inverting amplifier, the main microphone is electrically connected with the inverting amplifier, and the first adder and the inverting amplifier are both electrically connected with the gain adjusting circuit; the amplification factor of the inverting amplifier is obtained by dividing the total number of the auxiliary microphones by the total number of the main microphones;
the first adding unit is used for receiving the sound signals and adding the sound signals to generate a first audio signal;
the input amplification unit is used for receiving the sound signal and amplifying the sound signal to generate a second audio signal;
the gain adjusting circuit is used for adjusting the gain of the second audio signal according to the gain of the first audio signal so as to enable the gain of the first audio signal to be equal to the gain of the second audio signal and outputting a first sound adjusting signal and a second sound adjusting signal;
the subtraction circuit is used for subtracting the first sound adjustment signal and the second sound adjustment signal and amplifying the two sound adjustment signals to obtain a third audio signal subjected to noise reduction.
2. The acoustic noise reduction circuit of claim 1, wherein the plurality of secondary microphones are symmetrically distributed about the center of the primary microphone, and wherein the plurality of secondary microphones and the primary microphone are all in the same plane.
3. The acoustic noise reduction circuit of claim 1, wherein the input amplification unit includes a plurality of primary microphones and a second summer, the plurality of primary microphones each being electrically connected to the second summer, and the second summer being electrically connected to the gain adjustment circuit.
4. The acoustic noise reduction circuit of claim 3, wherein the plurality of secondary microphones are symmetrically distributed about a center point of the plurality of primary microphones, and wherein the plurality of secondary microphones and the plurality of primary microphones are all coplanar.
5. The acoustic noise reduction circuit of claim 1, further comprising a band limiting circuit electrically coupled to the subtraction circuit, the band limiting circuit configured to limit a passband of the third audio signal to a preset frequency range and output a fourth audio signal.
6. The acoustic noise reduction circuit of claim 5, further comprising an output circuit electrically coupled to the band limiting circuit, the output circuit configured to impedance transform the fourth audio signal to a noise reduced output signal.
7. The acoustic noise reduction circuit of claim 1, wherein the gain adjustment circuit comprises a voltage divider circuit, a first voltage follower, a potentiometer, and a second voltage follower;
the voltage division circuit is electrically connected between the first adding unit and the first voltage follower, the potentiometer is electrically connected between the input amplifying unit and the second voltage follower, and the first voltage follower and the second voltage follower are both electrically connected with the subtraction circuit.
8. A microphone, characterized in that the microphone comprises the acoustic noise reduction circuit of any one of claims 1 to 7.
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| WO1997023068A2 (en) * | 1995-12-15 | 1997-06-26 | Philips Electronic N.V. | An adaptive noise cancelling arrangement, a noise reduction system and a transceiver |
| JP2002171591A (en) * | 2000-12-04 | 2002-06-14 | Sony Corp | Stereophonic microphone system, noise reduction processing method and system |
| JP4196162B2 (en) * | 2002-08-20 | 2008-12-17 | ソニー株式会社 | Automatic wind noise reduction circuit and automatic wind noise reduction method |
| CN1209889C (en) * | 2003-04-21 | 2005-07-06 | 徐忠义 | Phoneme background noise inhibitor |
| CN2694649Y (en) * | 2004-04-05 | 2005-04-20 | 辅升电子科技(深圳)有限公司 | Microphone input circuit capable removing noises |
| CN104768104B (en) * | 2015-02-09 | 2017-11-24 | 江苏海湾电气科技有限公司 | Environment resistant noise peculiar to vessel and anti-microphone circuit of uttering long and high-pitched sounds |
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