CN114024560B - Echo suppression and howling prevention voice intercom system based on program-controlled electronic attenuator - Google Patents
Echo suppression and howling prevention voice intercom system based on program-controlled electronic attenuator Download PDFInfo
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- CN114024560B CN114024560B CN202111532562.7A CN202111532562A CN114024560B CN 114024560 B CN114024560 B CN 114024560B CN 202111532562 A CN202111532562 A CN 202111532562A CN 114024560 B CN114024560 B CN 114024560B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B1/0475—Circuits with means for limiting noise, interference or distortion
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/3827—Portable transceivers
- H04B1/3833—Hand-held transceivers
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
- G10L2021/02082—Noise filtering the noise being echo, reverberation of the speech
Abstract
The invention discloses an echo suppression and howling prevention voice intercom system based on a program-controlled electronic attenuator, which comprises a signal processing module consisting of a preamplifier A, an attenuator A, a power amplifier A, a preamplifier B, an attenuator B, a power amplifier B and a singlechip, wherein howling suppression and echo suppression can be realized by acquiring a voice amplification signal A output by the preamplifier A and a voice amplification signal B output by the preamplifier B, comparing the voice amplification signals A and B with a normal range of voice signals and judging whether howling exists or not, and carrying out logic control on the attenuator A and the attenuator B when the howling exists; the method has the advantages of strong environmental adaptability, capability of realizing full-duplex communication, no need of mastering a complex digital filter algorithm, lower application threshold, lower computation amount, no need of DSP (digital signal processor) processing, capability of processing by a simple single chip microcomputer and scheme cost reduction.
Description
Technical Field
The invention relates to an echo suppression and howling prevention voice intercom system, in particular to an echo suppression and howling prevention voice intercom system based on a program-controlled electronic attenuator.
Background
The voice intercom system is used for bidirectional voice communication between two rooms and mainly comprises two electro-acoustic conversion modules and a signal processing module, wherein each electro-acoustic conversion module comprises a microphone and a loudspeaker, and the two electro-acoustic conversion modules are arranged in the two rooms in a one-to-one correspondence mode. The two rooms are respectively called a room A and a room B, and the two electroacoustic conversion modules are respectively called an electroacoustic conversion module A and an electroacoustic conversion module B, wherein the electroacoustic conversion module A comprises a microphone A and a loudspeaker A, and the electroacoustic conversion module B comprises a microphone B and a loudspeaker B. The microphone a and the speaker a are disposed in the a room, and the microphone B and the speaker B are disposed in the B room. When the A room is communicated with the B room, sound collected by a microphone A positioned in the A room is transmitted to a loudspeaker B positioned in the B room for playing after being processed by a signal processing module; the same principle is applied to the reverse direction communication. Because the microphone and the loudspeaker in the same room cannot be isolated acoustically, the following problems occur in the voice intercom system: (1) echo: the sound received by the microphone A is processed by the signal processing module and then transmitted to the loudspeaker B for playing, the sound is received by the microphone B and then returned to the loudspeaker A for playing by the signal processing module, and the signal loops back to generate echo; the same principle is applied to the reverse direction communication. (2) howling: the howling is caused by the following two factors: (1) when the two-way communication is carried out, the microphone A and the loudspeaker A are close to each other, or the microphone B and the loudspeaker B are close to each other, the sound played by the loudspeaker A is received by the microphone A, the sound played by the loudspeaker B is received by the microphone B (sound isolation is difficult to realize in the same room), and the sound forms a closed loop through the system, so that the loudspeakers A and B generate howling; (2) when the telephone is in one-way communication, the two rooms are close to each other or the doors of the rooms are open, the sound of the loudspeaker A is received by the microphone B, the sound of the loudspeaker B is received by the microphone A (no sound isolation exists between the rooms), the sound can loop back through the air, and the sound is transmitted through the air to form a closed loop, so that the loudspeaker A or B generates howling.
There are currently two main solutions to the above-mentioned echo and howling problems. In the first scheme, the signal processing module is implemented based on a dedicated chip, and in the second scheme, the signal processing module is implemented based on a Digital Signal Processor (DSP). The first solution has low cost, high chip integration level and simple application, but has the following disadvantages: 1. only half duplex, that is, when one direction is talking, the other direction is prevented from talking; 2. the system can not work normally and abnormal phenomena such as sound interruption and the like occur in a noisy environment or when a sound source is far away from a microphone; 3. parameters of the resistance-capacitance device on the periphery of the special chip need to be matched according to an application scene, and debugging and optimization difficulty is high. The second scheme utilizes an audio signal processing algorithm to suppress spectral components which may generate howling and echo, so as to realize full-duplex communication, and software automatically identifies the distance between a sound source and a microphone, and automatically controls gain, so that the environment adaptability is strong, but the second scheme has the following disadvantages: 1. the cost for the CPU is large and the cost is high; 2. the software algorithm has high complexity and high application threshold.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an echo suppression and howling prevention voice intercom system based on a program-controlled electronic attenuator, which has low cost and low application threshold, can realize full-duplex communication and has strong environmental adaptability.
The technical scheme adopted by the invention for solving the technical problems is as follows: a voice intercom system for suppressing echo and preventing howling based on a program-controlled electronic attenuator comprises two electroacoustic conversion modules and a signal processing module, wherein the two electroacoustic conversion modules are respectively called an electroacoustic conversion module A and an electroacoustic conversion module B, the electroacoustic conversion module A comprises a microphone A and a loudspeaker A, the electroacoustic conversion module B comprises a microphone B and a loudspeaker B, the signal processing module comprises a preamplifier A, an attenuator A, a power amplifier A, a preamplifier B, an attenuator B, a power amplifier B and a single chip microcomputer, the output end of the microphone A is connected with the input end of the preamplifier A, the output end of the preamplifier A is respectively connected with the input end of the attenuator A and the single chip microcomputer, the output end of the attenuator A is connected with the input end of the power amplifier A, the output end of the power amplifier A is connected with the input end of the loudspeaker B, the output end of the microphone B is connected with the input end of the preamplifier B, the output end of the preamplifier B is respectively connected with the input end of the attenuator B and the input end of the single chip microcomputer, the output end of the attenuator B is connected with the output end of the power amplifier B, and the input end of the loudspeaker A are connected with the input end of the attenuator B;
in operation, the microphone A and the loudspeaker A are arranged in a room A, and the microphone B and the loudspeaker B are arranged in a room B; the microphone A is used for collecting voice signals in a room A and sending the voice signals to the preamplifier A, the preamplifier A is used for amplifying the received voice signals to obtain voice amplified signals A which are output at the output end of the preamplifier A, the microphone B is used for collecting the voice signals in the room B and sending the voice amplified signals A to the preamplifier B, the preamplifier B is used for amplifying the received voice signals to obtain voice amplified signals B which are output at the output end of the preamplifier B, a 12-bit multichannel ADC is arranged in the single chip microcomputer and is used for collecting the voice amplified signals A at the output end of the preamplifier A and the voice amplified signals B at the output end of the preamplifier B, an environmental background noise level threshold value, a loudspeaker voice level threshold value and a direct human voice level threshold value are prestored in the single chip microcomputer, the environmental background noise level threshold value is smaller than the loudspeaker voice level threshold value, the loudspeaker voice level threshold value is smaller than the direct human voice level threshold value, and the voice amplified signals A and the voice amplified signals B at the output end of the preamplifier B are periodically collected from the output end of the preamplifier A and the preamplifier B;
when the voice amplification signal A acquired by the preamplifier A and the voice amplification signal B acquired by the preamplifier B are both smaller than or equal to the background noise level threshold of the environment by the singlechip, it indicates that no conversation is carried out between the room A and the room B, and the singlechip controls the attenuator A and the attenuator B to be switched off and stop working;
when the single chip microcomputer is used for acquiring a voice amplification signal A from the preamplifier A, wherein the voice amplification signal A is larger than a loudspeaker sound level threshold value, and the voice amplification signal B acquired from the preamplifier B is larger than an environmental background noise level threshold value and is smaller than or equal to the loudspeaker sound level threshold value, the single chip microcomputer indicates that one-way call from a room A to the room B is currently carried out, the single chip microcomputer controls the attenuator A to enable the voice amplification signal A to be attenuated through the attenuator A and generate a corresponding voice attenuation signal A to be output to the power amplifier A, the power amplifier A is used for carrying out power amplification on the voice attenuation signal A and then playing voice through the loudspeaker B, in the one-way call process from the room A to the room B, the single chip microcomputer controls the attenuator B to be always in a turn-off state, a reverse call path is cut off, echo is prevented, the single chip microcomputer monitors whether howling occurs in real time, when the single chip microcomputer monitors that the voice amplification signal B is larger than a direct human sound level threshold value, the single chip microcomputer judges that howling occurs, and when the howling occurs, the single chip microcomputer controls the following steps: the single chip microcomputer controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplification signal B monitored by the single chip microcomputer is greater than an environmental background noise level threshold and less than or equal to a loudspeaker sound level threshold, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A to reduce the sound played by the loudspeaker B again if howling occurs again in the sound increasing process of the loudspeaker B until a balance state is reached and the howling is released;
when the voice amplification signal B acquired by the singlechip from the preamplifier B is greater than a speaker sound level threshold value, and the voice amplification signal A acquired by the preamplifier A is greater than an environment background noise level threshold value and is less than or equal to the speaker sound level threshold value, it is indicated that one-way call from the room B to the room A is currently performed, the singlechip controls the attenuator B to enable the voice amplification signal B to be attenuated by the attenuator B and generate a corresponding voice attenuation signal B to be output to the power amplifier B, the power amplifier B performs power amplification on the voice attenuation signal B and then broadcasts voice through the speaker A, in the one-way call process from the room B to the room A, the singlechip controls the attenuator A to be always in an off state, a reverse direction call path is cut off, echo is prevented, the singlechip monitors whether howling occurs in real time, when the singlechip monitors that the voice amplification signal A is greater than a direct human sound level threshold value, the singlechip judges that howling occurs, and when the howling occurs, the singlechip controls the singlechip as follows: the single chip microcomputer controls the attenuator B to reduce the sound played by the loudspeaker A for squeal suppression until the voice amplification signal A monitored by the single chip microcomputer is larger than an environmental background noise level threshold and smaller than or equal to a loudspeaker sound level threshold, then controls the attenuator B to gradually increase the sound played by the loudspeaker A, and controls the attenuator B to reduce the sound played by the loudspeaker A again if squeal occurs again in the sound increasing process played by the loudspeaker A until a balanced state is reached and the squeal is removed;
when the single-chip microcomputer monitors that the voice amplification signal B is greater than the direct voice level threshold value, the voice amplification signal B is judged to be a howling sound control signal, and the howling sound control signal is as follows: the single chip microcomputer controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplification signal B monitored by the single chip microcomputer is greater than an environmental background noise level threshold and less than or equal to a loudspeaker sound level threshold, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A to reduce the sound played by the loudspeaker B again if howling occurs again in the sound increasing process played by the loudspeaker B, and the process is repeated until a balance state is reached within preset howling adjustment time, the howling is released or the balance state is not reached within the preset howling adjustment time; when the singlechip monitors that the voice amplification signal A is larger than the direct human voice level threshold value, the singlechip judges that howling occurs, and at the moment, the singlechip controls the following steps: the singlechip controls the attenuator B to reduce the sound played by the loudspeaker A for squealing inhibition until the voice amplification signal A monitored by the singlechip is larger than an environmental background noise level threshold and is smaller than or equal to a loudspeaker sound level threshold, then controls the attenuator B to gradually improve the sound played by the loudspeaker A, and controls the attenuator B to reduce the sound played by the loudspeaker A again if squealing occurs again in the sound improvement process played by the loudspeaker A, and the process is repeated until the balance state is reached within the preset squealing adjustment time, the squealing is released or the balance state is not reached within the preset squealing adjustment time; when the balance state is not reached within the preset howling adjustment time, the single chip microcomputer controls the attenuator A and the attenuator B to periodically and alternately turn off and normally work to realize bidirectional communication, wherein one of the attenuator A and the attenuator B is turned off and the other one of the attenuator A and the attenuator B normally works at the same time, and the period time is 30ms-100ms.
The attenuator A is provided with 5 attenuation steps, the attenuation coefficients of the 5 attenuation steps are respectively 100%, 75%, 50%, 25% and 0%, when the attenuation coefficient is 100%, the attenuator A directly outputs the volume of the voice amplification signal A connected to the input end of the attenuator A as the voice attenuation signal A at the output end of the attenuator A, when the attenuation coefficient is 75%, the attenuator A reduces the volume of the voice amplification signal A connected to the input end of the attenuator A to 75% and outputs the voice amplification signal A at the output end of the attenuator A, when the attenuation coefficient is 50%, the attenuator A reduces the volume of the voice amplification signal A connected to the input end of the attenuator A to 50% and outputs the voice amplification signal A at the output end of the attenuator A, when the attenuation coefficient is 25%, the attenuator A reduces the volume of the voice amplification signal A connected to the input end of the attenuator A to 25% and outputs the voice amplification signal A as the voice attenuation signal A at the output end of the attenuator A, when the attenuation coefficient is 0%, the attenuator A reduces the volume of the voice amplification signal A connected to 0% and outputs the attenuation signal A at the output end of the attenuator A, namely, and the attenuator A is in an off state; the attenuator A comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, a second switch, a third switch, a fourth switch and a fifth switch, wherein the first resistor, the second resistor, the third resistor and the fourth resistor have the same resistance value, one end of the first resistor is connected with one end of the first switch, the connection end of the first resistor is the input end of the attenuator A, the other end of the first resistor, one end of the second resistor and one end of the second switch are connected, the other end of the second resistor, one end of the third resistor and one end of the third switch are connected, the other end of the third resistor, one end of the fourth resistor and one end of the fourth switch are connected, the other end of the fourth resistor and one end of the fifth switch are all grounded, the other end of the first switch, the other end of the second switch, the other end of the third switch, the other end of the fourth switch and one end of the fifth switch are connected, when the attenuation coefficient of the attenuator A is turned on, the attenuation coefficient of the attenuator A is 0, and the attenuation coefficient of the attenuator A is controlled by the first switch, the second switch, the attenuator A and the singlechip, the attenuator A is turned on, and the attenuation of the singlechip, when the attenuator is turned on; when the fifth switch is turned off, any two of the first switch, the second switch, the third switch and the fourth switch cannot be turned on simultaneously, at this time, when any one of the first switch, the second switch, the third switch and the fourth switch is turned on, the attenuator A enters a working state, when the first switch is turned on, the attenuation coefficient of the attenuator A is 100%, when the second switch is turned on, the attenuation coefficient of the attenuator A is 75%, when the third switch is turned on, the attenuation coefficient of the attenuator A is 50%, and when the fourth switch is turned on, the attenuation coefficient of the attenuator A is 25%; the attenuator B is identical to the attenuator A.
Compared with the prior art, the voice signal processing method has the advantages that the signal processing module is formed by the preamplifier A, the attenuator A, the power amplifier A, the preamplifier B, the attenuator B, the power amplifier B and the single chip microcomputer, the voice amplification signal A output by the preamplifier A and the voice amplification signal B output by the preamplifier B are collected and then compared with the normal range of the voice signal to judge whether howling exists, when the howling exists, the howling suppression and echo suppression can be realized by logically controlling the attenuator A and the attenuator B, the environmental adaptability is strong, full-duplex communication can be realized, a complex digital filter algorithm does not need to be mastered, the application threshold is low, the operation amount is low, the DSP processing is not needed, the simple single chip microcomputer can process the voice signal processing method, and the scheme cost is reduced.
Drawings
FIG. 1 is a block diagram of an echo suppression and howling prevention voice intercom system based on a programmable electronic attenuator according to the present invention;
fig. 2 is a circuit diagram of an attenuator a of the echo suppression and howling prevention voice intercom system based on the programmable electronic attenuator.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Example (b): as shown in fig. 1, an echo suppression and howling prevention voice intercom system based on a program-controlled electronic attenuator comprises two electroacoustic conversion modules and a signal processing module, wherein the two electroacoustic conversion modules are respectively called an electroacoustic conversion module a and an electroacoustic conversion module B, the electroacoustic conversion module a comprises a microphone a and a loudspeaker a, and the electroacoustic conversion module B comprises a microphone B and a loudspeaker B, and is characterized in that the signal processing module comprises a preamplifier a, an attenuator a, a power amplifier a, a preamplifier B, an attenuator B, a power amplifier B and a single chip microcomputer; in operation, the microphone A and the loudspeaker A are arranged in the room A, and the microphone B and the loudspeaker B are arranged in the room B; the microphone A is used for collecting voice signals in a room A and sending the voice signals to the preamplifier A, the preamplifier A is used for amplifying the received voice signals to obtain voice amplified signals A which are output at the output end of the preamplifier A, the microphone B is used for collecting the voice signals in the room B and sending the voice amplified signals to the preamplifier B, the preamplifier B is used for amplifying the received voice signals to obtain voice amplified signals B which are output at the output end of the preamplifier B, a 12-bit multichannel ADC is arranged in the single chip microcomputer and is used for collecting the voice amplified signals A at the output end of the preamplifier A and the voice amplified signals B at the output end of the preamplifier B, an environment background noise level threshold value, a loudspeaker voice level threshold value and a direct human voice level threshold value are prestored in the single chip microcomputer, the environment background noise level threshold value is smaller than the loudspeaker voice level threshold value, the loudspeaker voice level threshold value is smaller than the direct human voice level threshold value, and the single chip microcomputer periodically collects the voice amplified signals A from the output end of the preamplifier A and collects the voice amplified signals B at the output end of the preamplifier B;
when the voice amplification signal A collected by the preamplifier A and the voice amplification signal B collected by the preamplifier B by the singlechip are both smaller than or equal to the background noise level threshold of the environment, the fact that no communication is carried out between the room A and the room B is indicated, and the singlechip controls the attenuator A and the attenuator B to be turned off and stop working; when the single chip microcomputer monitors whether howling occurs or not in real time, when the single chip microcomputer monitors that the voice amplification signal B is greater than a direct human sound level threshold value, the single chip microcomputer judges that howling occurs, and when the howling occurs, the single chip microcomputer controls the following control steps: the singlechip controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplified signal B monitored by the singlechip is greater than the background noise level threshold of the environment and less than or equal to the sound level threshold of the loudspeaker, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A again to reduce the sound played by the loudspeaker B in the process of increasing the sound played by the loudspeaker B if howling occurs again until the balance state is reached, and the howling is removed; when the single chip microcomputer detects that the voice amplification signal A is greater than the direct human sound level threshold value, the single chip microcomputer judges that howling occurs, and when the howling occurs, the single chip microcomputer controls the following steps: the singlechip controls the attenuator B to reduce the sound played by the loudspeaker A for howling suppression until the voice amplified signal A monitored by the singlechip is greater than the background noise level threshold of the environment and less than or equal to the sound level threshold of the loudspeaker, then controls the attenuator B to gradually increase the sound played by the loudspeaker A, and controls the attenuator B again to reduce the sound played by the loudspeaker A in the process of increasing the sound played by the loudspeaker A if howling occurs again until the balance state is reached and the howling is removed; when the single chip microcomputer detects that the voice amplification signal B is greater than the voice level threshold value of a loudspeaker, the single chip microcomputer controls the attenuator A to enable the voice amplification signal A to be attenuated through the attenuator A and then generate a corresponding voice attenuation signal A to be output to the power amplifier A, the power amplifier A performs power amplification on the voice attenuation signal A and then broadcasts voice through the loudspeaker B, the single chip microcomputer controls the attenuator B to enable the voice amplification signal B to be attenuated through the attenuator B and then generate a corresponding voice attenuation signal B to be output to the power amplifier B, the power amplifier B performs power amplification on the voice attenuation signal B and then broadcasts voice through the loudspeaker A, the single chip microcomputer monitors whether howling occurs in real time in the two-way call process of the room A and the room B, when the single chip microcomputer detects that the voice amplification signal B is greater than the direct human voice level threshold value, the single chip microcomputer judges that the howling occurs, and controls the following steps: the singlechip controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplified signal B monitored by the singlechip is greater than the background noise level threshold of the environment and less than or equal to the sound level threshold of the loudspeaker, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A to reduce the sound played by the loudspeaker B again if the howling occurs again in the sound increasing process played by the loudspeaker B, and the steps are repeated until the balance state is reached within the preset howling adjustment time, the howling is released or the balance state is not reached within the preset howling adjustment time; when the singlechip monitors that the voice amplification signal A is greater than the direct human voice level threshold value, the singlechip judges that howling occurs, and the singlechip performs the following control: the singlechip controls the attenuator B to reduce the sound played by the loudspeaker A for howling suppression until the voice amplified signal A monitored by the singlechip is larger than the background noise level threshold of the environment and smaller than or equal to the sound level threshold of the loudspeaker, then controls the attenuator B to gradually increase the sound played by the loudspeaker A, and controls the attenuator B again to reduce the sound played by the loudspeaker A if howling occurs again in the sound increasing process played by the loudspeaker A, and the steps are repeated until the balance state is reached within the preset howling adjustment time, the howling is released or the balance state is not reached within the preset howling adjustment time; when the balance state is not reached within the preset howling adjustment time, the single chip microcomputer controls the attenuator A and the attenuator B to be periodically and alternately turned off and normally work to realize bidirectional communication, wherein one of the attenuator A and the attenuator B is turned off and the other one of the attenuator A and the attenuator B normally works at the same time, and the period time is 30-100 ms.
As shown in fig. 2, in the present embodiment, the attenuator a has 5 attenuation steps, the attenuation coefficients of the 5 attenuation steps are 100%, 75%, 50%, 25% and 0%, when the attenuation coefficient is 100%, the attenuator a directly outputs the sound volume of the voice amplified signal a received at the input terminal thereof as the voice attenuated signal a at the output terminal thereof, when the attenuation coefficient is 75%, the attenuator a reduces the sound volume of the voice amplified signal a received at the input terminal thereof to 75% and outputs the voice amplified signal a at the output terminal thereof, when the attenuation coefficient is 50%, the attenuator a reduces the sound volume of the voice amplified signal a received at the input terminal thereof to 50% and outputs the voice attenuated signal a at the output terminal thereof, when the attenuation coefficient is 25%, the attenuator a reduces the sound volume of the voice amplified signal a received at the input terminal thereof to 25% and outputs the voice attenuated signal a at the output terminal thereof, when the attenuation coefficient is 0%, the attenuator a reduces the sound volume of the voice amplified signal a received at the input terminal thereof to 0% and outputs the voice amplified signal a as the attenuated signal a at the output terminal thereof, that is in an off state; the attenuator A comprises a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4 and a fifth switch K5, wherein the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 have the same resistance value, one end of the first resistor R1 is connected with one end of the first switch K1, the connection end of the first resistor R1 is the input end of the attenuator A, the other end of the first resistor R1, one end of the second resistor R2 and one end of the second switch K2 are connected, the other end of the second resistor R2, one end of the third resistor R3 and one end of the third switch K3 are connected, the other end of the third resistor R3, one end of the fourth resistor R4 and one end of the fourth switch K4 are connected, the other end of the fourth resistor R4 and one end of the fifth switch K5 are both grounded, the other end of the first switch K1, the other end of the second switch K2, the other end of the third switch K3, the other end of the fourth switch K4 and the other end of the fifth switch K5 are connected, the connecting end of the first switch K1, the other end of the second switch K2, the other end of the third switch K3 and the other end of the fourth switch K4 are connected, the connecting end of the first switch K1, the second switch K2, the third switch K3, the fourth switch K4 and the fifth switch K5 is the output end of the attenuator A, the single chip microcomputer controls the attenuation gear of the attenuator A by controlling the conducting and disconnecting states of the first switch K1, the second switch K2, the third switch K3, the fourth switch K4 and the fifth switch K5, when the fifth switch K5 is conducted, the attenuator A is turned off, and the attenuation coefficient of the attenuator A is 0; when the fifth switch K5 is turned off, any two of the first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 cannot be turned on simultaneously, at this time, when any one of the first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 is turned on, the attenuator a enters a working state, when the first switch K1 is turned on, the attenuation coefficient of the attenuator a is 100%, when the second switch K2 is turned on, the attenuation coefficient of the attenuator a is 75%, when the third switch K3 is turned on, the attenuation coefficient of the attenuator a is 50%, and when the fourth switch K4 is turned on, the attenuation coefficient of the attenuator a is 25%; attenuator B is identical to attenuator A.
Claims (2)
1. A voice intercom system for suppressing echo and preventing howling based on a program-controlled electronic attenuator comprises two electroacoustic conversion modules and a signal processing module, wherein the two electroacoustic conversion modules are respectively called an electroacoustic conversion module A and an electroacoustic conversion module B, the electroacoustic conversion module A comprises a microphone A and a loudspeaker A, and the electroacoustic conversion module B comprises a microphone B and a loudspeaker B, and the voice intercom system is characterized in that the signal processing module comprises a preamplifier A, an attenuator A, a power amplifier A, a preamplifier B, an attenuator B, a power amplifier B and a singlechip, the output end of the microphone A is connected with the input end of the preamplifier A, the output end of the preamplifier A is respectively connected with the input end of the attenuator A and the singlechip, the output end of the attenuator A is connected with the input end of the power amplifier A, the output end of the power amplifier A is connected with the input end of the loudspeaker B, the output end of the microphone B is connected with the input end of the preamplifier B, the output end of the preamplifier B is respectively connected with the input end of the attenuator B and the input end of the loudspeaker B;
in operation, the microphone A and the loudspeaker A are arranged in a room A, and the microphone B and the loudspeaker B are arranged in a room B; the microphone A is used for collecting voice signals in a room A and sending the voice signals to the preamplifier A, the preamplifier A is used for amplifying the received voice signals to obtain voice amplified signals A which are output at the output end of the preamplifier A, the microphone B is used for collecting the voice signals in the room B and sending the voice amplified signals A to the preamplifier B, the preamplifier B is used for amplifying the received voice signals to obtain voice amplified signals B which are output at the output end of the preamplifier B, a 12-bit multichannel ADC is arranged in the single chip microcomputer and is used for collecting the voice amplified signals A at the output end of the preamplifier A and the voice amplified signals B at the output end of the preamplifier B, an environmental background noise level threshold value, a loudspeaker voice level threshold value and a direct human voice level threshold value are prestored in the single chip microcomputer, the environmental background noise level threshold value is smaller than the loudspeaker voice level threshold value, the loudspeaker voice level threshold value is smaller than the direct human voice level threshold value, and the voice amplified signals A and the voice amplified signals B at the output end of the preamplifier B are periodically collected from the output end of the preamplifier A and the preamplifier B;
when the voice amplification signal A acquired by the preamplifier A and the voice amplification signal B acquired by the preamplifier B are both smaller than or equal to the background noise level threshold of the environment by the singlechip, it indicates that no conversation is carried out between the room A and the room B, and the singlechip controls the attenuator A and the attenuator B to be switched off and stop working;
when the single chip microcomputer acquires a voice amplification signal A from the preamplifier A, which is greater than a speaker sound level threshold value, and a voice amplification signal B acquired from the preamplifier B, which is greater than an environmental background noise level threshold value and less than or equal to a speaker sound level threshold value, which indicates that a one-way call from the room A to the room B is currently performed, the single chip microcomputer controls the attenuator A to enable the voice amplification signal A to be attenuated by the attenuator A and generate a corresponding voice attenuation signal A to be output to the power amplifier A, the power amplifier A performs power amplification on the voice attenuation signal A and then broadcasts voice by the speaker B, the single chip microcomputer controls the attenuator B to be always in an off state in the one-way call process from the room A to the room B, a reverse direction call path is cut off to prevent echo, and the single chip microcomputer monitors whether howling occurs in real time, when the single chip microcomputer monitors that the voice amplification signal B is greater than a direct human sound level threshold value, the single chip microcomputer judges that the howling occurs, and when the howling occurs, the single chip microcomputer performs the following control: the single chip microcomputer controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplification signal B monitored by the single chip microcomputer is greater than an environmental background noise level threshold and less than or equal to a loudspeaker sound level threshold, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A to reduce the sound played by the loudspeaker B again if howling occurs again in the sound increasing process of the loudspeaker B until a balance state is reached and the howling is removed;
when the voice amplification signal B acquired by the singlechip from the preamplifier B is greater than a speaker sound level threshold value, and the voice amplification signal A acquired by the preamplifier A is greater than an environment background noise level threshold value and is less than or equal to the speaker sound level threshold value, it is indicated that one-way call from the room B to the room A is currently performed, the singlechip controls the attenuator B to enable the voice amplification signal B to be attenuated by the attenuator B and generate a corresponding voice attenuation signal B to be output to the power amplifier B, the power amplifier B performs power amplification on the voice attenuation signal B and then broadcasts voice through the speaker A, in the one-way call process from the room B to the room A, the singlechip controls the attenuator A to be always in an off state, a reverse direction call path is cut off, echo is prevented, the singlechip monitors whether howling occurs in real time, when the singlechip monitors that the voice amplification signal A is greater than a direct human sound level threshold value, the singlechip judges that howling occurs, and when the howling occurs, the singlechip controls the singlechip as follows: the single chip microcomputer controls the attenuator B to reduce the sound played by the loudspeaker A for squeal suppression until the voice amplification signal A monitored by the single chip microcomputer is larger than an environmental background noise level threshold and smaller than or equal to a loudspeaker sound level threshold, then controls the attenuator B to gradually increase the sound played by the loudspeaker A, and controls the attenuator B to reduce the sound played by the loudspeaker A again if squeal occurs again in the sound increasing process played by the loudspeaker A until a balanced state is reached and the squeal is removed;
when the single chip microcomputer monitors whether whistling occurs or not in the bidirectional call process between the room A and the room B, the single chip microcomputer judges that whistling occurs and controls the following steps: the single chip microcomputer controls the attenuator A to reduce the sound played by the loudspeaker B for howling suppression until the voice amplification signal B monitored by the single chip microcomputer is greater than an environmental background noise level threshold and less than or equal to a loudspeaker sound level threshold, then controls the attenuator A to gradually increase the sound played by the loudspeaker B, and controls the attenuator A to reduce the sound played by the loudspeaker B again if howling occurs again in the sound increasing process played by the loudspeaker B, and the process is repeated until a balance state is reached within preset howling adjustment time, the howling is released or the balance state is not reached within the preset howling adjustment time; when the singlechip monitors that the voice amplification signal A is larger than the direct human voice level threshold value, the singlechip judges that howling occurs, and at the moment, the singlechip controls the following steps: the singlechip controls the attenuator B to reduce the sound played by the loudspeaker A for squealing inhibition until the voice amplification signal A monitored by the singlechip is larger than an environmental background noise level threshold and is smaller than or equal to a loudspeaker sound level threshold, then controls the attenuator B to gradually improve the sound played by the loudspeaker A, and controls the attenuator B to reduce the sound played by the loudspeaker A again if squealing occurs again in the sound improvement process played by the loudspeaker A, and the process is repeated until the balance state is reached within the preset squealing adjustment time, the squealing is released or the balance state is not reached within the preset squealing adjustment time; when the balance state is not reached within the preset howling adjustment time, the single chip microcomputer controls the attenuator A and the attenuator B to periodically and alternately turn off and normally work to realize bidirectional communication, wherein one of the attenuator A and the attenuator B is turned off and the other one of the attenuator A and the attenuator B normally works at the same time, and the period time is 30ms-100ms.
2. The echo suppression and howling prevention voice intercom system based on a programmable electronic attenuator according to claim 1, characterized in that the attenuator A has 5 attenuation steps, the attenuation coefficients of the 5 attenuation steps are respectively 100%, 75%, 50%, 25% and 0%, when the attenuation coefficient is 100%, the attenuator A keeps the volume of the voice amplification signal A connected to the input end unchanged and directly outputs the voice amplification signal A as the voice attenuation signal A at the output end, when the attenuation coefficient is 75%, the attenuator A reduces the volume of the voice amplification signal A connected to the input end to 75% and outputs the voice amplification signal A as the voice attenuation signal A at the output end, when the attenuation coefficient is 50%, the attenuator A reduces the volume of the voice amplification signal A connected to the input end to 50% and outputs the voice amplification signal A at the output end, when the attenuation coefficient is 25%, the attenuator A reduces the volume of the voice amplification signal A connected to 25% and outputs the voice attenuation signal A as the voice attenuation signal A at the output end, when the attenuation coefficient is 0%, the attenuator A reduces the volume of the voice amplification signal A to 0% and outputs the attenuation signal A at the output end; the attenuator A comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, a second switch, a third switch, a fourth switch and a fifth switch, wherein the first resistor, the second resistor, the third resistor and the fourth resistor have the same resistance value, one end of the first resistor is connected with one end of the first switch, the connection end of the first resistor is the input end of the attenuator A, the other end of the first resistor, one end of the second resistor and one end of the second switch are connected, the other end of the second resistor, one end of the third resistor and one end of the third switch are connected, the other end of the third resistor, one end of the fourth resistor and one end of the fourth switch are connected, the other end of the fourth resistor and one end of the fifth switch are all grounded, the other end of the first switch, the other end of the second switch, the other end of the third switch, the other end of the fourth switch and one end of the fifth switch are connected, when the attenuation coefficient of the attenuator A is turned on, the attenuation coefficient of the attenuator A is 0, and the attenuation coefficient of the attenuator A is controlled by the first switch, the second switch, the attenuator A and the singlechip, the attenuator A is turned on, and the attenuation of the singlechip, when the attenuator is turned on; when the fifth switch is turned off, any two of the first switch, the second switch, the third switch and the fourth switch cannot be turned on simultaneously, at this time, when any one of the first switch, the second switch, the third switch and the fourth switch is turned on, the attenuator A enters a working state, when the first switch is turned on, the attenuation coefficient of the attenuator A is 100%, when the second switch is turned on, the attenuation coefficient of the attenuator A is 75%, when the third switch is turned on, the attenuation coefficient of the attenuator A is 50%, and when the fourth switch is turned on, the attenuation coefficient of the attenuator A is 25%; the attenuator B is identical to the attenuator A.
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