WO2016058232A1 - 音频降噪电路、采用该音频降噪电路的智能终端机及教学方法 - Google Patents

音频降噪电路、采用该音频降噪电路的智能终端机及教学方法 Download PDF

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Publication number
WO2016058232A1
WO2016058232A1 PCT/CN2014/090547 CN2014090547W WO2016058232A1 WO 2016058232 A1 WO2016058232 A1 WO 2016058232A1 CN 2014090547 W CN2014090547 W CN 2014090547W WO 2016058232 A1 WO2016058232 A1 WO 2016058232A1
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WIPO (PCT)
Prior art keywords
pin
audio
terminal
microphone
input
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PCT/CN2014/090547
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English (en)
French (fr)
Inventor
卢启伟
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深圳市时尚德源文化传播有限公司
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Publication of WO2016058232A1 publication Critical patent/WO2016058232A1/zh

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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
    • G09B5/00—Electrically-operated educational appliances
    • G09B5/06—Electrically-operated educational appliances with both visual and audible presentation of the material to be studied
    • G09B5/065—Combinations of audio and video presentations, e.g. videotapes, videodiscs, television systems
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques 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
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques 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
    • G10L21/0316—Speech enhancement, e.g. noise reduction or echo cancellation by changing the amplitude
    • 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
    • H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques 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
    • G10L21/0272—Voice signal separating
    • 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
    • H04R2410/05—Noise reduction with a separate noise microphone

Definitions

  • the invention relates to an education training method and device, and particularly relates to a network-based interactive teaching method, an intelligent terminal device device and an audio noise reduction circuit applied to the smart terminal device.
  • multimedia intelligent terminal devices have gradually entered the teaching field, which greatly enriched the teaching methods, so that teaching and learning are not restricted by the regional environment and other conditions, changing the traditional teaching methods. , to achieve a networked teaching method.
  • Network teaching refers to the use of the characteristics and resources of the Internet based on intelligent terminals to establish a networked learning environment to promote and support students' learning activities. Through the combination of network technology and classroom teaching, it realizes teaching across time and across time and space, and realizes personalized learning.
  • the basic principle of the current network teaching method is: storing the audio information of the pre-recorded educator in the intelligent terminal machine, and correspondingly uploading the information to the network teaching platform system, and the learner correspondingly reads the information for learning. .
  • This way of network teaching has the following drawbacks:
  • the intelligent terminal is an extremely important terminal device in the network teaching system.
  • the current intelligent terminal is mainly based on tablet computers, and corresponding to the corresponding teaching software installed on the tablet computer, there is a great shortage of information for collecting teacher audio information.
  • the quality of audio information directly determines the effect of teaching, while the current intelligent terminal can not effectively filter the environmental noise and ensure the quality of audio data;
  • the learning content stored in the current intelligent terminal is preset in it, and its learning mode is relatively fixed.
  • the learner is relatively monotonous, boring, and poor in learning during learning;
  • the current teaching method can not achieve real-time interaction between the learner and the learner, and the daily courseware of the educator cannot be placed on the tablet for the learner to learn.
  • the object of the present invention is to provide an audio noise reduction circuit to solve the problem that the current audio information is not well filtered when the audio information is collected, and the audio data quality cannot be guaranteed.
  • the present invention adopts the following technical solutions:
  • An audio noise reduction circuit includes: an audio input circuit, an audio amplification buffer circuit, an audio noise reduction processing chip, a filter circuit, and a power amplification circuit.
  • the audio noise reduction circuit further includes:
  • the audio input circuit includes a microphone MIC1, a microphone MIC_CON1 and an input switching circuit
  • the input switching circuit includes an input microphone switching switch chip U545
  • the microphone MIC1 is connected with a JACK_MIC_0_NO pin of the microphone switching switch chip U545, and the microphone MIC_CON1 and the microphone are switched.
  • the JACK_MIC_0_NC pin of the switch chip U545 is connected, and the microphone MIC1 and the microphone MIC_CON1 are used to input the collected audio signal containing the noise into the input switching circuit, and are switched from the COM pin through the microphone switching switch chip U545, and from the COM.
  • the audio signal passes through the filter inductor L530 to the output terminal MIC_0;
  • the audio amplification buffer circuit includes a circuit for respectively amplifying and buffering the audio signals input by the microphone MIC1 and the microphone MIC_CON1, wherein the circuit for amplifying and buffering the input audio signal of the microphone MIC1 includes capacitors C888, C889, C890, C891, C892, C893
  • the 3rd pin of the operational amplifier U544A is amplified by the operational amplifier U544A and then output by the 1st pin of the operational amplifier U544A, and then passed through the DC blocking capacitor C889 to the output terminal XMIC_0.
  • the circuit for amplifying and buffering the input audio signal of the microphone MIC_CON1 includes There are capacitors C895, C896, C897, C898, C899, operational amplifier U544B, resistors R838, R839, R840, R841, R842, R843; the input terminal MIC_1 is connected to the JACK_MIC_0_NC pin of the microphone switch chip U545 through the test point TP24, and the input terminal MIC_1 is input to the operational amplifier after DC blocking capacitor C895 U544B's 5th foot, after The amplification buffer of the operational amplifier U544B is output by the 7th pin of the operational amplifier U544B, and then passes through the DC blocking capacitor C896 to the output terminal XMIC_1;
  • the audio noise reduction processing chip comprises a clock interface, a USB interface, an audio interface, a dual channel I2SDAC interface, a dual channel I2S interface, a digital microphone interface and a dual channel I2S ADC interface;
  • the clock interface includes a 12MHz crystal input pin XTAL_I, 12MHz The crystal output pin XTAL_O and the clock input pin D_CLK_IN;
  • the USB interface includes a USB_DM pin and a USB_DP pin;
  • the audio interface includes a common mode input signal reference pin XACREFL/XACREFR, a left channel microphone input pin XMICL, and a right channel microphone input pin.
  • the dual channel I2S DAC interface includes I2S main clock pin DAC_MCLK, I2S Bit clock pin DAC_BCLK, I2S serial data pin DAC_DOUT, I2S left/right clock pin DAC_LRCK, data input pin DAC_DIN;
  • the dual channel I2S interface includes I2S bit clock D_I2S_BCLK, I2S data input D_I2S_DI, I2S left/right clock D_I2S_LRCK, 2S serial data D_I2S_DO;
  • the digital microphone interface includes digital wheat Wind clock input pin D_DMO_CLK, digital microphone clock output pin D_DMI_CLK, digital microphone data input pin D_DMI_DAT, digital microphone data output pin D_DMO_DAT; the dual channel I2
  • the steady-state noise and the non-stationary noise are separated, the speech extraction and separation are performed, and the extracted and separated speech signals are passed through the left channel output pin XLNOUTL and the right channel of the audio noise reduction processing chip.
  • Filter circuit including input terminal LOUT_L_OUT, LOUT_R_OUT, filter inductor L546, L547, DC blocking capacitor C944, C945; after audio noise reduction processing chip noise reduction processing, the extracted and separated speech signal passes through the left channel line output pin XLNOUTL, input The LOUT_L_OUT input is filtered to the filter inductor L546, and then output through the DC blocking capacitor C944 from the LOUT_L terminal. After the audio noise reduction processing chip is denoised, the extracted and separated speech signal passes through the right channel line output pin XLNOUTR. The terminal LOUT_R_OUT is input to the filter inductor L547 for filtering processing, and then output through the DC blocking capacitor C945 from the LOUT_R terminal;
  • the power amplifier circuit includes DC blocking capacitors C875 and C876, power amplifier chip U543, filter inductors L531, L533, L535, L536.
  • the voice signal output by the LOUT_L terminal after being filtered by the filter circuit is input to the power amplifier chip through the DC blocking capacitor C875.
  • U543, after being amplified by the power amplifier chip U543, is output to the speaker through the filter inductors L531 and L533 respectively; after being filtered by the filter circuit, the voice signal output by the LOUT_R terminal is input to the power amplifier chip U543 through the DC blocking capacitor C876, and the power is passed.
  • the amplifier chip U543 is amplified and then output to the speaker through a series of filter inductors L535 and L536.
  • any one of the voice signals input by the microphone MIC1 and the microphone MIC_CON1 is used as a background noise detection signal, and the other one is used as a voice detection signal, and the microphone MIC1 and the microphone MIC_CON1 are at a distance of 5 ⁇ 20CM different locations.
  • the audio noise reduction processing chip in the audio noise reduction circuit is a CM6571 chip; the microphone switching switch chip U545 is a SGM3157YC6 chip; the operational amplifiers U544A and U544B are NJM2746V chips, and the power amplification chip U543 is an NS4251 chip.
  • the audio input circuit is connected to the CPU through the USB interfaces USB_DM and USB_DP of the audio noise reduction processing chip CM6571.
  • the invention uses a dual microphone array to eliminate noise, and uses the ICA algorithm to perform blind source analysis, so that the amplitude of the far field noise received by the two microphones is substantially the same, and for the near field sound source, the received amplitudes are greatly different. Algorithm separation can get better results.
  • the present invention is for steady-state noise by superimposing power spectra in the frequency domain and then using filtering to eliminate; and for non-stationary noise, by different Two microphones in the position process the received signal, according to different characteristics of phase, amplitude, frequency, signal-to-noise ratio, etc., thereby separating all undesired steady-state noise and non-stationary noise, thereby realizing Denoising, source localization and tracking, speech extraction and separation improve speech quality in noisy environments.
  • the invention uses double MIC environmental noise elimination technology to eliminate noise by more than 30dB, and can also provide echo cancellation and single MIC noise reduction function, and the user can get clear voice call or recording effect in noisy environment.
  • the invention also provides an intelligent terminal machine with the above-mentioned audio noise reduction circuit, which realizes the real-time recording of the teaching audio data by real-time collecting and recording the audio information of the teaching person, and solves the learning content preset intelligent terminal machine, learning It is relatively monotonous, tedious, and poorly studied.
  • An intelligent terminal device comprising:
  • the main body includes a bottom case and a middle frame, and a main board, a liquid crystal screen and a touch screen are fixedly mounted between the bottom case and the middle frame, and the main board and the liquid crystal screen are electrically connected through an FPC connector;
  • An open slot is disposed at the rear end, and a receiving slot is disposed at the rear end of the middle frame.
  • the receiving slot is correspondingly located in the open slot, and the flip slot is further provided with a flip cover that can be flipped open, the flip cover After the plate is turned over, a sealing cavity can be formed corresponding to the receiving groove;
  • the high-scoring device is disposed in the accommodating groove, and includes a main bracket, a sub-bracket, and a photographing rod.
  • One end of the main bracket is rotatably connected to a connecting member fixedly mounted in the accommodating groove through a rotating shaft member, and the other end is Then, the first vertical rotating shaft is movably connected to one end of the auxiliary bracket, the auxiliary bracket can be opened or closed perpendicular to the main bracket about the first vertical rotating shaft; the other end of the auxiliary bracket passes through a horizontal rotating shaft and a second vertical rotating shaft and the photographing rod
  • the movable connecting rod can be opened or closed perpendicular to the auxiliary bracket around the second vertical rotating shaft, and is turned horizontally around the horizontal rotating shaft when the photographing rod is in an open state.
  • the motherboard is provided with a battery, a 3G module, a SIM card slot and a motherboard circuit including an audio noise reduction circuit, and the 3G module and the SIM card slot are connected to the battery through the motherboard circuit.
  • the sub-bracket includes a sub-bracket upper cover, a sub-bracket lower cover, and is mounted on the sub-bracket A circuit board between the cover and the lower cover of the sub-mount, the circuit board being electrically connected to the main board through a line disposed in the main support.
  • the camera bar includes a camera pole upper cover, a camera pole lower cover, and a camera module and a microphone mounted between the camera pole upper cover and the camera bar lower cover, and the camera module is electrically connected to the circuit board.
  • the camera module is provided with a camera.
  • the main board is further provided with an IC card slot for inserting an IC card and a magnetic card head for reading magnetic card magnetic stripe information, and the IC card slot and the magnetic card magnetic head are both connected to the main board circuit.
  • a rear end of the bottom case is further provided with a jack in which an electromagnetic pen is fixed.
  • a rear support pad is disposed at the bottom of the rear end of the bottom case, and a front support pad is disposed at the bottom of the front end.
  • the intelligent terminal device of the invention adopts an audio noise reduction circuit, and uses two microphones to collect audio signals, one is mounted on the host, one is mounted on the camera pole, and the two microphones first absorb the peripheral sound, and then input to the audio.
  • the noise reduction circuit uses an audio algorithm to distinguish the sound closest to the device, such as the distance of 60CM-300CM to collect and distinguish the human sound wavelength, so as to judge the audio signal close to the distance as the user's voice, thereby reducing the noise effect.
  • the present invention also provides a teaching system and method, which combines the above intelligent terminal device with a network to realize real-time interaction between teaching and learning.
  • the present invention adopts the following technical solutions:
  • a web-based teaching system that includes:
  • At least two of the aforementioned intelligent terminal devices one of which is a teaching terminal, and the other is a learning terminal;
  • a background server for storing the course information recorded and uploaded by the teaching terminal, and matching the course information by recording the ID and time stamp of the course;
  • the teaching terminal, the learning terminal, and the background server are connected through a network;
  • the teaching terminal is configured to record a teacher course, and upload and save in a background server in a manner of data stream and audio stream;
  • the learning terminal is configured to obtain an ID of the recorded course, and correspondingly read and time from the background server Poke the corresponding data stream and audio stream.
  • teaching terminal the teaching terminal, the learning terminal, and the background server are connected by wireless or wired network communication.
  • system further includes a projection device communicatively coupled to the teaching terminal.
  • the data stream is a lecture time and action information recorded by the teaching terminal in the teacher multimedia classroom
  • the audio stream is a class time and voice information recorded by the teaching terminal in the teacher multimedia classroom.
  • the invention also provides a web-based teaching method, comprising the steps of:
  • S1 recording a teacher course through the teaching terminal, and uploading and saving in a background server by means of data stream and audio stream;
  • the learning terminal acquires an ID of the recorded course from the background server, and correspondingly reads the data stream and the audio stream corresponding to the timestamp from the background server.
  • step S1 the method includes:
  • the communication connection includes a wired network connection and a WIFI, 3G, 4G wireless network connection.
  • the ID corresponding to the recorded course is set at the same time.
  • step S2 the method further includes:
  • the learning terminal feeds back information to the teaching terminal through the background server, and the teaching terminal answers the feedback information corresponding to the feedback information, wherein the feedback information includes an electronic text document established by the learning terminal or a handwritten paper document scanned by a high-shooter camera.
  • the teaching terminal actively initiates a question, asks the designated learning terminal to answer, and gives feedback after the end of the answer; or the teaching terminal actively initiates a question, the learning terminal performs a feedback response, and after the teaching terminal makes a selection, the selected one is selected.
  • the teaching system and method of the invention can realize the teacher's daily electronic lesson plan and the on-site courseware Real-time uploading enables foreign students or parents to watch anytime, anywhere, and realize the wireless sharing of high-quality teachers.
  • This system uploads and saves the teacher's lesson plans and video materials through the web server, avoiding the teacher's resignation or retirement.
  • the invention is based on the network-based teaching method, realizing the real-time synchronous feedback of teachers and students teaching and learning, and has the advantages of strong interaction and good learning effect.
  • FIG. 1 is a circuit schematic diagram of an audio noise reduction processing chip of the present invention
  • FIG. 2 is a circuit schematic diagram of an audio input circuit of the present invention
  • FIG. 3 is a circuit schematic diagram of an audio amplification buffer circuit of the present invention.
  • FIG. 4 is a circuit schematic diagram of a filter circuit of the present invention.
  • Figure 5 is a circuit schematic diagram of a power amplifying circuit of the present invention.
  • Figure 6 is a schematic view of the use state of the intelligent terminal device of the present invention.
  • FIG. 7 is a second schematic diagram of the use state of the intelligent terminal device of the present invention.
  • Figure 8 is a third schematic view of the use state of the intelligent terminal device of the present invention.
  • FIG. 9 is a schematic structural diagram of an intelligent terminal device according to the present invention.
  • Figure 10 is a schematic diagram of the network connection of the teaching system of the present invention.
  • FIG. 11 is a schematic diagram of recording of a teaching end course in the teaching system of the present invention.
  • FIG. 12 is a schematic diagram of a review of a learning end course in the teaching system of the present invention.
  • Figure 13 is a flow chart showing the implementation of the teaching method of the present invention.
  • the illustration shows the main body 1, the bottom case 11, the open slot 111, the jack 112, the front support pad 113, the support pad 114, the card cover 115, the main board 12, the battery 121, the FPC connector 122, the magnetic card head 123, and the IC card.
  • the invention provides an audio noise reduction circuit, in order to record audio and video in a professional studio where a teacher needs to go to a professional studio, the teaching conditions on the spot are limited, the audio recording effect is loud, and the problem of synchronous recording teaching cannot be performed.
  • the present invention includes an audio input circuit, an audio amplification buffer circuit, an audio noise reduction processing chip, a filter circuit, and a power amplification circuit.
  • FIG. 2 is a circuit schematic diagram of an audio input circuit of the present invention.
  • the audio input circuit in this embodiment includes an input switching circuit and two microphones (microphone MIC1 and microphone MIC_CON1).
  • the two microphones are used to collect voice signals containing noise (two paths respectively), wherein any one of them can be selected as the detection signal of the background noise, and the other one is used as the detection signal of the voice, and the two microphones (the two microphones)
  • the microphone MIC1, microphone MIC_CON1) are in different positions, and the distance between them is 5-20CM.
  • the input switching circuit includes an input microphone switching switch chip U545, which corresponds to the SGM3157YC6 chip.
  • the microphone MIC1 is connected to the pin 1 (JACK_MIC_0_NO) of the microphone switch chip U545 to input an audio signal through the microphone MIC1;
  • the microphone MIC_CON1 is connected to the pin 3 (JACK_MIC_0_NC) of the microphone switch chip U545 to input an audio signal through the microphone MIC_CON1;
  • the pin 3 (COM) of the microphone switch chip U545 is an output pin, which corresponds to JACK_MIC_0 and is connected to the filter inductor L530 and is divided into two outputs, one corresponding to the output terminal MIC_0, and the other pass through the resistors R823 and R822.
  • the output terminal MIC_BAISI is also grounded through the capacitor C877 between the resistors R823 and R822.
  • the microphone MIC1 and the microphone MIC_CON1 input the collected audio signal containing noise to the input switching circuit, and are switched from the COM pin through the microphone switching switch chip U545, and the switched audio signal output from the COM pin passes through the filter inductor. After L530, it goes to the output terminal MIC_0 and corresponds to the input to the audio amplification buffer circuit.
  • FIG. 3 is a circuit schematic diagram of an audio amplification buffer circuit of the present invention.
  • the audio amplification buffer circuit comprises two parts. The first part amplifies and buffers the audio signal input by the microphone MIC1, and the second part amplifies and buffers the audio signal input by the microphone MIC_CON1.
  • the first part of the circuit includes capacitors C888, C889, C890, C891, C892, C893, operational amplifier U544A, resistors R831, R832, R833, R834, R835 and R836; operational amplifier U544A is NJM2746V chip, capacitor C888 is DC blocking capacitor, The U544A pin 3 is connected to the capacitor C888.
  • a resistor R832 is connected between the capacitor C888 and the U544A pin 3. The other end of the resistor R832 is divided into two paths, one through the capacitor C890 and the other through the resistor R833.
  • the U544A's pin 2 is divided into two paths.
  • U544A pin 1 One is connected to the U544A pin 1 through the resistor R834, and the other is grounded through the resistors R836 and C891.
  • the U544A pin 1 passes through the capacitor C889 and the resistor R831 to the output XMIC_0. .
  • the switched audio signal of the COM pin output of the microphone switching switch chip U545 passes through the filter inductor L530, and is output from the output terminal MIC_0 through the DC blocking capacitor C888 to the pin 3 of the operational amplifier U544A, and is amplified by the operational amplifier U544A.
  • the pin 1 of the amplifier U544A is output, and then passes through the DC blocking capacitor C889 to the output terminal XMIC_0.
  • the second part of the circuit includes capacitors C895, C896, C897, C898, C899, operational amplifier U544B, resistors R838, R839, R840, R841, R842, R843; operational amplifier U544B is NJM2746V chip, capacitor C895 is DC blocking capacitor, U544B Pin 5 is connected to capacitor C895.
  • a resistor R839 is connected between pin C895 and pin 5 of U544B. The other end of the resistor R839 is divided into two paths. One is grounded through capacitor C898, and the other is connected through resistor R840.
  • the U544B's 6th leg is divided into two paths.
  • U544B pin 7 One is connected to the U544B pin 7 through the resistor R841, and the other is grounded through the resistors R843 and C899.
  • the U544B pin 7 passes through the capacitor C896 and the resistor R838 to the output terminal XMIC_1.
  • the input terminal MIC_1 of the second part of the circuit is connected to the JACK_MIC_0_NC pin of the microphone switching switch chip U545 through the test point TP24, and the input terminal MIC_1 is input to the pin 5 of the operational amplifier U544B through the DC blocking capacitor C895, and is amplified by the operational amplifier U544B. After The output of the 7th pin of the operational amplifier U544B is passed through the DC blocking capacitor C896 to the output terminal XMIC_1 and input to the audio noise reduction processing chip.
  • FIG. 1 is a circuit schematic diagram of an audio noise reduction processing chip of the present invention.
  • the above audio input circuit and audio amplification buffer circuit are peripheral circuits of the audio noise reduction processing chip, wherein the audio noise reduction processing chip is a CM6571 chip, and the CM6571 is used as a processing core for automatic echo cancellation, adopting voice processing technology, and is applied in voice and In terms of communication and other aspects of communication, it can effectively reduce ambient noise (ENC), and has functions such as long-distance intelligent voice capture (SVC), voice enhancement (HD VOICE), background noise cancellation (AEC), and long-distance recording (LDR).
  • SVC long-distance intelligent voice capture
  • HD VOICE voice enhancement
  • AEC background noise cancellation
  • LDR long-distance recording
  • the audio noise reduction processing chip includes a clock interface, a USB interface, a power ground interface, an audio interface, a dual channel I2S DAC interface, a dual channel I2S interface, a digital microphone interface, a dual channel I2S ADC interface, and an S/PDIF I/O interface.
  • Programmable IO section main serial bus interface and setup pin section.
  • the clock interface includes a 12 MHz crystal input pin XTAL_I, a 12 MHz crystal output pin XTAL_O, and a clock input pin D_CLK_IN.
  • the USB interface includes a USB_DM pin and a USB_DP pin, both of which are USB2.0 data interfaces, wherein the USB interface can be connected to the CPU, and the CPU corresponds to a central processing unit chip for data communication with the CM6571.
  • Power grounding interface includes 5V digital circuit power supply DV50, 1.8V power supply VCC18IO, +3.3V output XV33, digital ground GND18IO/GND3IO, 5V analog power supply AV50, analog ground AGND, +3.5V supply voltage XV35_DAC, +3.5V reference voltage XV35_ADC +3.5V drive voltage XV35_DRIVER, filter capacitor D_XV24_DA, analog ground D_AGND, analog power supply D_AVDD, reference voltage, capacitor ground D_XVREF, digital power supply D_DVDD, PLL power supply, capacitor ground D_XV1.2, digital ground D_DGND.
  • 5V digital circuit power supply DV50 1.8V power supply VCC18IO, +3.3V output XV33, digital ground GND18IO/GND3IO
  • 5V analog power supply AV50 analog ground AGND
  • +3.5V supply voltage XV35_DAC +3.5V reference voltage XV35_ADC +3.5V drive voltage XV35_DRI
  • the audio interface includes a common mode input signal reference pin XACREFL/XACREFR, a left channel microphone input pin XMICL, a right channel microphone input pin XMICR, an analog microphone 1 differential input pin D_MIC1_N, an analog microphone 0 differential input pin D_MIC0_N, an analog microphone 1 differential input pin.
  • D_MIC1_P analog microphone 0 differential input pin D_MIC0_P, left channel line input pin XLINL, right channel line input pin XLINR, microphone reference voltage 2.75V pin XMICBIAS2 and XMICBIAS1, reference voltage capacitor grounding pin XVAG, control analog voltage output pin XVOLADJ, Left channel line output pin XLNOUTL, no capacitor line output pin XLOCOM, right channel line output pin XLNOUTR, auxiliary differential input P pin D_AUXIN_P, auxiliary differential input N pin D_AUXIN_N.
  • the dual I2S DAC interface includes an I2S main clock pin DAC_MCLK, an I2S bit clock pin DAC_BCLK, an I2S serial data pin DAC_DOUT, an I2S left/right clock pin DAC_LRCK, and a data input pin DAC_DIN.
  • the dual channel I2S interface includes an I2S bit clock D_I2S_BCLK, an I2S data input D_I2S_DI, an I2S left/right clock D_I2S_LRCK, and 2S serial data D_I2S_DO.
  • the digital microphone interface includes a digital microphone clock input pin D_DMO_CLK, a digital microphone clock output pin D_DMI_CLK, a digital microphone data input pin D_DMI_DAT, and a digital microphone data output pin D_DMO_DAT.
  • the dual-channel I2S ADC interface includes analog-to-digital conversion data output pin ADC_DOUT, I2S left/right clock pin ADC_LRCK, I2S serial data input pin ADC_DIN, I2S bit clock pin ADC_BCLK, and I2S main clock pin ADC_MCLK.
  • the S/PDIF I/O interface includes the S/PDIF transmit pin SPDIF_O; the programmable IO portion includes the general-purpose programmable I/O pins GPIO_10 to GPIO_18; the main serial bus interface includes the 2-wire main serial data pin I2C_SDAT_0, 2 Line serial clock pin I2C_SCLK_0, I2C clock pin D_I2C_CLK_1, I2C data pin D_I2C_DAT_1; setting pins include related state pin PDSW, test pin TEST_0, test pin D_TEST_1, operating mode select pin D_MSEL_0, reset pin D_RSTN.
  • the microphone MIC1 audio signal after being amplified and buffered by the audio amplification buffer circuit is input to the left channel microphone input pin XMICL through the output terminal XMIC_0; the microphone MIC_CON1 audio signal after being amplified and buffered by the audio amplification buffer circuit is input to the right channel through the output terminal XMIC_1.
  • Microphone input pin XMICR audio noise reduction processing chip eliminates noise through input analog two-channel audio signal through analog microphone and digital microphone interface array, and performs blind source analysis through ICA algorithm to separate steady-state noise and non-stationary noise for voice The extraction and separation are performed, and the extracted and separated speech signals are output to the filter circuit through the left channel line output pin XLNOUTL and the right channel line output pin XLNOUTR of the audio noise reduction processing chip.
  • the audio noise reduction processing chip CM6571 used in the present invention uses a dual microphone array to eliminate noise, and uses the ICA algorithm for blind source analysis, the microphone MIC1 and the microphone MIC_CON1.
  • the far-field noise amplitude received by the wind is basically the same, and for the near-field sound source, the received amplitudes are very different, and the algorithm can be separated to obtain a better effect.
  • the noise is divided into steady-state noise and non-stationary noise. For steady-state noise, the power spectrum is superimposed in the frequency domain, and then filtered to eliminate. For non-stationary noise, two microphones at different positions are received.
  • the signal is processed, and through various characteristics such as phase, amplitude, frequency, signal-to-noise ratio, etc., all undesired steady-state noise and non-stationary noise are separated, and denoising, source localization and tracking, and speech extraction can be realized. And separation to improve the quality of speech in noisy environments.
  • FIG. 4 is a circuit schematic diagram of a filter circuit of the present invention.
  • the filter circuit includes an input terminal LOUT_L_OUT, LOUT_R_OUT, a filter inductor L546, L547, a DC blocking capacitor C942, C943, C944, C945, and a resistor R923, R924.
  • a DC blocking capacitor C943 is connected between the input terminal LOUT_L_OUT and the filter inductor L546, and the DC blocking capacitor C943 is grounded; the filter inductor L546 is connected to the C944, and a resistor R924 is connected between the two, and is grounded through the resistor R924; the input terminal LOUT_R_OUT A DC blocking capacitor C942 is connected between the filter inductor L547 and the DC blocking capacitor C942 is grounded.
  • the filter inductor L547 is connected to C945, and a resistor R923 is connected between the two, and is grounded through the resistor R923.
  • the extracted and separated speech signal passes through the left channel line output pin XLNOUTL, is input to the filter inductor L546 through the input terminal LOUT_L_OUT for filtering processing, and then output through the DC blocking capacitor C944 from the LOUT_L terminal;
  • the extracted and separated speech signal passes through the right channel line output pin XLNOUTR, is input to the filter inductor L547 through the input terminal LOUT_R_OUT for filtering processing, and then is outputted by the LOUT_R terminal through the DC blocking capacitor C945.
  • FIG. 5 is a circuit schematic diagram of a power amplifying circuit of the present invention.
  • the power amplifier circuit of the embodiment includes a DC blocking capacitor C875, C876, C879, C880, C881, C882, C883, C884, C886, a power amplifier chip U543, a filter inductor L531, L533, L534, L535, L536, a resistor R819, R820, R823, R826, power amplifier chip U543 is NS4251 chip.
  • the DC blocking capacitor C875 is connected to the 8th pin INNA of the power amplifying chip U543 through the resistor R820, U543
  • the power supply pins VDD1 and VDD2 are connected to VDDSW through L534, and VDD1 and VDD2 are also grounded through C881 and C882.
  • the VREF pin of U543 is grounded through C883
  • the HP-IN pin is connected to the resistor R823
  • the DC blocking capacitor C876 is amplified by resistor R826 and power.
  • the pin 7 of the chip U543 is connected to the INNB.
  • the VONA pin and the VOPA pin of the power amplifying chip U543 constitute a set of output signals to the horn, wherein the VONA pin is output to the horn through the filter inductor L531, and a capacitor C879 is connected between the filter inductor L531 and the horn, and the capacitor C879 is grounded; U543 The VOPA pin is output to the horn through the filter inductor L533, and a capacitor C880 is connected between the filter inductor L533 and the horn, and the capacitor C880 is grounded.
  • the voice signal outputted by the LOUT_L terminal after being filtered by the filter circuit is input to the power amplifier chip U543 through the DC blocking capacitor C875, and amplified by the power amplifier chip U543, and then outputted to the speaker through a filter inductor L531 and L533 respectively.
  • the VONB pin and the VOPB pin of the power amplifier chip U543 constitute another set of output signals to the speaker, wherein the VONB pin is output to the speaker through the filter inductor L535, and a capacitor C884 is connected between the filter inductor L535 and the speaker, and the capacitor C884 is grounded; U543 The VOPB pin is output to the horn through the filter inductor L536, and a capacitor C886 is connected between the filter inductor L536 and the horn, and the capacitor C886 is grounded.
  • the voice signal outputted by the LOUT_R terminal is input to the power amplifier chip U543 through the DC blocking capacitor C876, and amplified by the power amplifier chip U543, and the other audio signals are output to the speaker through the filter inductors L535 and L536 respectively.
  • This circuit can eliminate noise by more than 30dB by using dual MIC ambient noise cancellation technology. It can also provide echo cancellation and single MIC noise reduction function. Users can get clear voice call or recording effect in noisy environment.
  • the invention also provides an intelligent terminal machine, which is mainly used in the field of education, and mainly aims at the present teaching intelligent terminal device having an audio information environment with high noise and low audio quality, and learning cannot be realized. Real-time synchronous feedback, poor interactivity, and poor learning.
  • the present invention has been improved in view of the prior art, and mainly includes a host 1 and a high beater.
  • the main body 1 includes a bottom case 11 and a middle frame 14 , and a main board 12 , a liquid crystal screen 13 and a touch screen 15 are fixedly mounted between the bottom case 11 and the middle frame 14 , and the main board 12 is provided with a main board circuit.
  • the mainboard circuit includes the above audio noise reduction circuit and a CPU chip, and the CPU and the CM6571 chip in the audio noise reduction circuit are connected through a USB interface.
  • the touch screen 15 is a capacitive electromagnetic composite double-layer touch screen, the upper layer is a capacitive screen, and the lower layer is an electromagnetic screen.
  • the main board 12 is further provided with a battery 121, a 3G module, a SIM card slot, an IC card slot 124 and a magnetic card head 123.
  • the 3G module, the SIM card slot, the IC card slot 124 and the magnetic card head 123 are all connected to the motherboard circuit.
  • the motherboard circuit is connected to the battery 121 and powered by the battery 121.
  • the magnetic card head 123 is used to read the magnetic card magnetic stripe information
  • the IC card slot 124 is used to insert the IC card and read the IC card information.
  • the invention can realize the card swiping of the bank card through the IC card slot and the magnetic card head, which is convenient for the on-site payment of the teaching and training institution, and can also realize the purpose of credit card sign-in and member management by issuing the membership card.
  • the main board 12 is provided with an FPC connector 122 through which the liquid crystal panel 13 can be connected.
  • An open slot 111 is disposed at a rear end of the bottom case 11.
  • the rear end of the middle frame 14 is provided with a receiving slot 2, and the receiving slot 2 is correspondingly located in the open slot 111, and is further disposed in the open slot 111.
  • the rear end of the bottom case 11 is further provided with a socket 112, wherein the electromagnetic pen 7 can be correspondingly fixed, and the electromagnetic pen 7 has a control circuit, an electromagnetic pen sensing module and a power supply battery, and the control circuit and the electromagnetic pen
  • the sensing module and the power supply battery are electrically connected, one end is an electromagnetic pen tip, the other end is a laser pen end, a noise reduction microphone is arranged in the middle of the electromagnetic pen, a noise reduction microphone is connected to the control circuit, and the control circuit is provided with a Bluetooth module for transmitting a sound signal.
  • the electromagnetic pen can not only be written directly on the touch screen, but also used as a microphone and laser remote control.
  • a cover 115 for fixing the 3G module is further disposed at the bottom of the bottom case 11.
  • a rear support pad 114 is disposed at the bottom of the rear end of the bottom case 11, and the bottom of the front end is provided with A front support pad 113 is provided to make the entire host 1 at a certain inclination angle, which is convenient for the user to view and use.
  • the high-scoring device is disposed in the accommodating groove 2, and includes a main bracket 4, a sub-bracket 5, and a photographing rod 6.
  • the one end of the main bracket 4 passes through the rotating shaft member 41 and the connecting member fixedly mounted in the accommodating groove 2 42 is rotatably connected, and the other end is movably connected to one end of the sub-bracket 5 through the first vertical rotating shaft 54.
  • the sub-mount 5 includes a sub-mount upper cover 51, a sub-mount lower cover 52, and a circuit board 53 mounted between the sub-mount upper cover 51 and the sub-mount lower cover 52, and the circuit board 53 passes through a line provided in the main support 4
  • the motherboard circuit on the motherboard 12 is connected.
  • the camera bar 6 includes a camera bar upper cover 61, a camera bar lower cover 62, and a camera module 63 and a microphone mounted between the camera bar upper cover 61 and the camera bar lower cover 62, and the camera module 63 and the circuit board 53 are electrically
  • the camera module 631 is provided on the camera module 63.
  • the sub-bracket 5 can be opened or closed perpendicular to the main bracket 4 about the first vertical rotating shaft 54. When opened, the sub-bracket 5 is perpendicular to the main bracket 4, and the sub-bracket 5 can rotate in the horizontal plane about the first vertical rotating shaft 54; At this time, the sub-bracket 5 overlaps with the main bracket 4 (see Figs. 6 and 7).
  • the other end of the sub-bracket 5 is movably connected to the photographing rod 6 through a horizontal rotating shaft 65 and a second vertical rotating shaft 64.
  • the photographing rod 6 can be opened or closed perpendicular to the auxiliary bracket 5 about the second vertical rotating shaft 64. When opened, the photographing rod 6 is opened.
  • the sub-bracket 5 can be opened to the same horizontal position, and the two are on the same horizontal line; when closed, the sub-bracket 5 and the photographing rod 6 are correspondingly overlapped (see FIGS. 6 and 7).
  • a horizontal rotating shaft 65 is further mounted between the photographing rod 6 and the auxiliary bracket 5.
  • the photographing rod 6 When the photographing rod 6 is opened relative to the auxiliary bracket 5, the two are on the same horizontal line. At this time, the photographing rod 6 is rotated in the vertical direction, and the photographing rod 6 is It is rotatable about the horizontal axis 65, corresponding to the end of the camera rod 6 on which the camera 631 and the microphone are mounted (see FIG. 8).
  • the smart terminal of the present invention is a tablet computer when viewed from the outside.
  • the Gao Paiyi can be taken out from the accommodating slot 2 and opened to the state in which it needs to work in a manner as shown in FIGS. 6-8.
  • the present invention can operate the entire intelligent terminal machine through the electromagnetic pen 7 provided to realize teaching.
  • the electromagnetic pen can greatly facilitate the online interaction between the teacher and the student.
  • the teacher's whiteboard can be broadcasted to the students remotely.
  • the high-scoring instrument can facilitate the teacher to answer questions in real time for the students.
  • the unclear questions can be uploaded directly by Gao Paiyi. It also facilitates online interaction between teachers and students.
  • the intelligent terminal device of the invention adopts an audio noise reduction circuit, and uses two microphones to collect audio signals, one is mounted on the host, one is mounted on the camera pole, and the two microphones first absorb the peripheral sound, and then input to the audio.
  • the noise reduction circuit uses an audio algorithm to distinguish the sound closest to the device, such as the distance of 60CM-300CM to collect and distinguish the human sound wavelength, so as to judge the audio signal close to the distance as the user's voice, thereby reducing the noise effect.
  • the sound within 3 meters can be collected and processed to distinguish the wavelength of the human voice. Finally, the processing is collected into the device, and the sound of 3 meters is processed by the noise.
  • the teaching system mainly includes at least two intelligent terminal devices, one of which is a teaching terminal and the other is a learning terminal.
  • the smart terminal adopts the IMX6 motherboard, the IMX6 motherboard has built-in Android system and system optimization unit, and the system optimization unit can optimize the bootloader, the Linux kernel, the Android Init process startup and the Android Server service startup, and the integration includes the pickup, AEC.
  • An audio unit composed of an echo cancellation module, an audio amplifier, an external speaker or a headphone; a video unit composed of a high-shooter camera and a video codec; an input unit composed of a touch screen, an electromagnetic pen, a LINE-IN interface, and a USB interface; Display unit composed of touch screen and HDMI interface; storage unit composed of flash memory, storage and TFT card slot; swipe unit consisting of magnetic stripe reading and writing, IC reading and writing, data decoding and encryption processing chip, and RJ45 interface, WIFI A communication unit consisting of a module and a 3G PCI-E module.
  • the teaching system of the present invention further includes a background server through which the teaching end can be stored
  • the recorded course information is recorded and matched with the course information by recording the course ID and time stamp.
  • the background server is deployed with CentOS 6.4 or above, and uses Mysql database for intelligent terminal interactive data including audio, video and text file storage, forming a directory and index for reading and calling, and also storing the system.
  • the event information, login information, and log information generated by the operation are used for the uploading and management of the courseware by the courseware editing management system.
  • the teaching terminal, the learning terminal and the background server are connected through a network, and the three can realize wired communication through the RJ45 interface, or realize wireless network communication through the WIFI module, the 3G PCI-E module and the 4G module.
  • the teaching terminal is configured to record a teacher course and upload and save it in a background server in a manner of data stream and audio stream; the learning terminal is configured to obtain an ID of the recorded course, and correspondingly read from the background server.
  • the data stream and audio stream corresponding to the timestamp.
  • the data stream is a lecture time and action information recorded by the teaching terminal in the teacher multimedia classroom;
  • the audio stream is a class time and voice information recorded by the teaching terminal in the teacher multimedia classroom.
  • the system includes a projection device in communication with the teaching terminal.
  • the projection device adopts a projector and a screen or a wide-screen display.
  • the teacher controls the terminal to connect the projection device through the HDMI interface, and displays the touch screen content of the terminal.
  • the system also includes a teacher PC end, the teacher logs in to the background server through the PC end class, downloads and installs the courseware editor, the editor source code is developed by C&C++ method, and multiple choice questions, multiple choice questions, judgments are based on the Office2010 Word version.
  • the problem is added and edited, and then uploaded to the background server to form the test courseware and the courseware analysis result are saved in the server by the XML document; the intelligent terminal machine uses the information of the courseware analysis to segment the courseware and generate the SWF title file, and performs the touch screen on the touch screen. Display, and the intelligent evaluation of the answer is that the student's answer is compared with the server-pre-stored answer. After the answer is completed, the score can be automatically calculated to facilitate the practice or test.
  • the intelligent terminal machine of the invention comprises a 3G PCI-E module, and the SIM card is inserted in the module, and the system can bind the SIM card communication number of the learning terminal used by the student to the mobile phone number of the student parent, and the student uses The parent's name and mobile phone number are registered on the server's profile account.
  • Parents can log in to the server through their own name and mobile phone number, by comparing the server with the parent login information. It is possible to log in to the student profile account so that parents can keep track of the student's class situation and scores.
  • the system has got rid of the traditional teaching system and methods consisting of fixed classrooms, podiums, lesson plans, textbooks, blackboards, chalks, etc., to realize a modern Internet interactive teaching method, free from the limitations of time and space, and to store electronic textbooks through the database to achieve lightening.
  • the burden of carrying heavy textbook textbooks has improved teaching efficiency, interactivity and fun.
  • the intelligent terminal device of the invention is light, compact and convenient to carry, and effectively solves the existing classroom teaching system.
  • the original desktop computer cabinet is cumbersome, takes up a large space, has many devices, has complicated wiring, is inconvenient to operate, and is difficult to troubleshoot.
  • the invention has the design of the HDMI interface connecting the projection device and the touch screen, realizes that the electromagnetic pen is directly written on the touch screen, replaces the writing of the computer input keyboard and the blackboard, and the operation is more convenient and quick, which is beneficial to improving the teaching quality and efficiency.
  • the invention inserts a SIM card through a 3G PCI-E module to realize connection to a 3G mobile network, and the mobile operator can realize binding with the parent smart phone terminal, and log in to the server student profile account to view the teacher background uploading to the server database. Student achievement statistics and homework situation, to understand the children's learning at school anytime, anywhere.
  • the above is a description of the network teaching system of the intelligent terminal machine of the present invention.
  • the network teaching method using the intelligent terminal machine will be further described below with reference to FIG. 13, wherein the network-based teaching method of the present invention includes the following steps:
  • the communication connection includes a wired network connection and a WIFI, 3G, 4G wireless network connection.
  • the teacher course is recorded through the teaching terminal, and is uploaded and saved in the background server in the manner of data stream and audio stream; wherein when the teacher course is recorded through the teaching terminal, the ID corresponding to the recorded course needs to be set at the same time.
  • the learning terminal acquires the ID of the recorded course from the background server, and correspondingly reads the data stream and the audio stream corresponding to the timestamp from the background server.
  • the learning terminal feeds back information to the teaching terminal through the background server, and the teaching terminal answers the corresponding information of the feedback information, wherein the feedback information includes an electronic text document established by the learning terminal or passes through the high A handwritten paper document scanned by the camera camera.
  • the teaching terminal initiates a question actively, requires the designated learning terminal to answer, and gives feedback after the end of the answer; or the teaching terminal initiates a question actively, the learning terminal performs a feedback response, and after the teaching terminal makes a selection, the selected learning terminal performs the Answer, and the teaching terminal gives feedback after the answer is over.
  • the intelligent terminal device of the invention can develop applications such as pre-course preparation, classroom teaching, after-school tutoring and distance education based on the Internet.
  • Prepare lessons before class teachers prepare lessons through intelligent terminal with Android operating system, start smart terminal, establish Word, PPT document editing courseware according to requirements, or scan handwritten paper lesson plans through Gao Paiyi camera; classroom teaching, teacher use
  • the teaching terminal machine the student uses the learning terminal machine, the teaching terminal machine and the learning terminal machine establish a network connection through the WIFI module or the RJ45 connection network cable, and adopts the TCP/IP multicast protocol to realize the master-slave control, and all the sub-control terminals simultaneously display
  • the main control terminal interface realizes multi-screen synchronous teaching;
  • the classroom teaching step can synchronously access the learning terminal machine in the cloud, and the learning terminal machine connects to the Internet through the communication unit to realize network connection with the background server, and log in to the remote education application through the network.
  • the student can start the terminal and log in to the server to download the job file uploaded by the teacher to the server; and directly input the answer content on the touch screen display, or write on the paper workbook, and then pass the high-shooter camera.
  • the scan forms a document and uploads it to the server.
  • the specific use is as follows: First, teachers and students use their personal terminals to use personal identification information to serve in the background through the network. Registering, the registration information is matched with the information stored in the database, and then the registration is completed; after that, the student logs into the network and enters the interactive question and answer application unit in the background server, and writes a question through the touch screen or scans the problem through the Gao Paiyi.
  • the teacher list is viewed in the interactive Q&A application unit, and the teacher details are clicked, and then the teacher is selected for solving; and the teacher uses the teaching terminal to log in to the interactive question answering unit module in the background server to view To answer the list of questions, then select the question, use the touch screen, electromagnetic pen writing or Gao Paiyi to scan the text, or use the Gao Paiyi to record the answering audio and video files to complete the answer upload; finally, the students will view the answered questions. List, download and view details of the issue and playback answers.
  • the present invention performs real-time recording of the multimedia of the teacher's online classroom (differential multimedia whiteboard explanation, answering intelligent achievement statistics, after-school audio discussion and speech, etc.), and the classroom speaking audio system, and the student passes the remote test guidance system. Or the on-demand review of the online lecture system, which enables an on-demand review of the recorded course.

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Abstract

一种音频降噪电路、采用该音频降噪电路的智能终端机及教学方法，该音频降噪电路包括音频输入电路、音频放大缓冲电路、音频降噪处理芯片、滤波电路和功率放大电路，采用双麦克风阵列消除噪音，利用ICA算法进行盲源分析，实现对语音的提取和分离，提高嘈杂环境下的语音质量，使用户在嘈杂的环境下也可以得到清晰的语音通话或录制效果；通过实时采集、录制教学者的音频信息，实现了教学音频数据实时录制，解决了学习内容预置智能终端机中，学习时相对单调，乏味，学习效果不佳的问题。实现了优质师资力量的无线分享以及老师、学生在教与学过程中的实时同步反馈，互动性强，学习效果好。

Description

音频降噪电路、采用该音频降噪电路的智能终端机及教学方法 技术领域
本发明涉及教育培训方法及设备，具体涉及的是一种基于网络的互动式教学方法、智能终端机设备以及应用于该智能终端机中的音频降噪电路。
背景技术
随着多媒体和网络通信技术的快速发展与普及，多媒体智能终端机设备逐渐进入教学领域，其极大丰富了教学手段，使教与学不在受到地域环境等条件的制约，改变了传统的教学方式，实现了网络化的教学方式。
网络教学是指以智能终端机为依据、利用互联网的功能特性和资源，建立网络化的学习环境，促进和支持学生的学习活动。其通过网络技术与课堂教学相结合，实现了跨越进度、跨越时空的教学，实现了个性化的学习。
目前的网络教学方式，其基本原理是：将预先录制好的教学者的音频信息存储在智能终端机中，并对应将这些信息上传到网络教学平台系统，由学习者对应读取该信息进行学习。这种网络教学的方式存在以下缺陷：
一、智能终端机是网络教学系统中极为重要的终端设备，目前的智能终端机主要以平板电脑为主，其对应在平板电脑上安装相应的教学软件，对于采集教师音频信息方面存在很大不足，尤其是在网络学习环境下，音频信息的质量直接决定了教学的效果，而目前的智能终端机则无法有效过滤环境噪音，保证音频数据质量；
二、目前的智能终端机内存储的学习内容是预置在里面的，其学习模式相对固定，学习者在学习时相对单调，乏味，学习效果不佳；
三、目前的教学方式不能实现教学者与学习者之间的实时互动，教学者每天的课件也不可能放置在平板上让学习者学习。
发明内容
为此，本发明的目的在于提供一种音频降噪电路，以解决目前音频信息在采集时，过滤效果不佳，音频数据质量无法保证的问题。
其中，为了解决上述问题，本发明采用如下技术方案：
一种音频降噪电路，包括：音频输入电路、音频放大缓冲电路、音频降噪处理芯片、滤波电路和功率放大电路。
进一步地，该音频降噪电路还包括：
音频输入电路，包括有麦克风MIC1、麦克风MIC_CON1和输入切换电路，所述输入切换电路包括有输入麦克风切换开关芯片U545；所述麦克风MIC1与麦克风切换开关芯片U545的JACK_MIC_0_NO脚连接，麦克风MIC_CON1与麦克风切换开关芯片U545的JACK_MIC_0_NC脚连接，麦克风MIC1和麦克风MIC_CON1用于将采集到的包含有噪音的音频信号输入到输入切换电路，并通过麦克风切换开关芯片U545进行切换处理后从COM脚输出，且从COM脚输出的切换后音频信号经过滤波电感L530后到输出端MIC_0；
音频放大缓冲电路，包括有对麦克风MIC1和麦克风MIC_CON1输入的音频信号分别进行放大缓冲的电路，其中对麦克风MIC1输入音频信号进行放大缓冲的电路包括有电容C888、C889、C890、C891、C892、C893，运算放大器U544A，电阻R831、R832、R833、R834、R835和R836；麦克风切换开关芯片U545的COM脚输出的切换后音频信号经过滤波电感L530后，由输出端MIC_0经过隔直流电容C888后输入到运算放大器U544A的3号脚，经过运算放大器U544A的放大缓冲之后由运算放大器U544A的1号脚输出，再经过隔直流电容C889后到输出端XMIC_0；对麦克风MIC_CON1输入音频信号进行放大缓冲的电路包括有电容C895、C896、C897、C898、C899，运算放大器U544B，电阻R838、R839、R840、R841、R842、R843；输入端MIC_1通过测试点TP24连接到麦克风切换开关芯片U545的JACK_MIC_0_NC脚，而输入端MIC_1经过隔直流电容C895后输入到运算放大器U544B的5号脚，经过 运算放大器U544B的放大缓冲之后由运算放大器U544B的7号脚输出，再经过隔直流电容C896后到输出端XMIC_1；
音频降噪处理芯片，包括有时钟接口、USB接口、音频接口、双通道I2SDAC接口、双通道I2S接口、数字麦克风接口和双通道I2S ADC接口；所述时钟接口包括有12MHz晶体输入脚XTAL_I、12MHz晶体输出脚XTAL_O和时钟输入脚D_CLK_IN；所述USB接口包括有USB_DM脚和USB_DP脚；所述音频接口包括有共模输入信号参考脚XACREFL/XACREFR、左通道麦克风输入脚XMICL、右通道麦克风输入脚XMICR、模拟麦克风1差分输入脚D_MIC1_N、模拟麦克风0差分输入脚D_MIC0_N、模拟麦克风1差分输入脚D_MIC1_P、模拟麦克风0差分输入脚D_MIC0_P；所述双通道I2S DAC接口包括有I2S主时钟脚DAC_MCLK、I2S位时钟脚DAC_BCLK、I2S串行数据脚DAC_DOUT、I2S左/右时钟脚DAC_LRCK、数据输入脚DAC_DIN；所述双通道I2S接口包括有I2S位时钟D_I2S_BCLK、I2S数据输入D_I2S_DI、I2S左/右时钟D_I2S_LRCK、2S串行数据D_I2S_DO；所述数字麦克风接口包括有数字麦克风时钟输入脚D_DMO_CLK、数字麦克风时钟输出脚D_DMI_CLK、数字麦克风数据输入脚D_DMI_DAT、数字麦克风数据输出脚D_DMO_DAT；所述双通道I2S ADC接口包括有模数转换数据输出脚ADC_DOUT、I2S左/右时钟脚ADC_LRCK、I2S串行数据输入脚ADC_DIN、I2S位时钟脚ADC_BCLK、I2S主时钟脚ADC_MCLK；其中经过音频放大缓冲电路放大缓冲之后的麦克风MIC1音频信号经过输出端XMIC_0后输入到左通道麦克风输入脚XMICL；经过音频放大缓冲电路放大缓冲之后的麦克风MIC_CON1音频信号经过输出端XMIC_1后输入到右通道麦克风输入脚XMICR；音频降噪处理芯片对输入的两路音频信号通过模拟麦克风和数字麦克风接口阵列消除噪音，并通过ICA算法进行盲源分析，分离出稳态噪声和非稳态噪声，进行语音提取和分离，并将提取和分离的语音信号经过音频降噪处理芯片的左通道线路输出脚XLNOUTL、右通道线路输出脚XLNOUTR输出；
滤波电路，包括输入端LOUT_L_OUT、LOUT_R_OUT，滤波电感L546、L547，隔直流电容C944、C945；经过音频降噪处理芯片降噪处理后，提取和分离的语音信号经过左通道线路输出脚XLNOUTL，由输入端LOUT_L_OUT输入到滤波电感L546进行滤波处理后，再经过隔直流电容C944由LOUT_L端输出；经过音频降噪处理芯片降噪处理后，提取和分离的语音信号经过右通道线路输出脚XLNOUTR，由输入端LOUT_R_OUT输入到滤波电感L547进行滤波处理后，再经过隔直流电容C945由LOUT_R端输出；
功率放大电路，包括隔直流电容C875、C876，功率放大芯片U543，滤波电感L531、L533、L535、L536，经过滤波电路滤波后由LOUT_L端输出的语音信号经过隔直流电容C875后输入到功率放大芯片U543，经过功率放大芯片U543放大后为一组分别经过滤波电感L531、L533输出到喇叭；经过滤波电路滤波后由LOUT_R端输出的语音信号经过隔直流电容C876后输入到功率放大芯片U543，经过功率放大芯片U543放大后为一组分别经过滤波电感L535、L536输出到喇叭.
进一步地，该音频降噪电路中所述麦克风MIC1、麦克风MIC_CON1输入的语音信号中任意一路作为背景噪音的检测信号，另外一路作为语音的检测信号，且所述麦克风MIC1、麦克风MIC_CON1处于距离为5～20CM的不同位置。
进一步地，该音频降噪电路中所述音频降噪处理芯片为CM6571芯片；麦克风切换开关芯片U545为SGM3157YC6芯片；运算放大器U544A、U544B均为NJM2746V芯片、功率放大芯片U543为NS4251芯片。
进一步地，所述音频输入电路通过音频降噪处理芯片CM6571的USB接口USB_DM和USB_DP与CPU连接。
本发明使用双麦克风阵列消除噪音，利用ICA算法进行盲源分析，使两个麦克风收到的远场噪声幅度是基本一样的，而对近场声源，收到的幅度就相差很大，通过算法分离就可以得到比较好的效果。本发明对于稳态噪声，通过在频域上进行功率谱的叠加，然后采用滤波消除；而对于非稳态噪声，通过不同 位置上的两个麦克风，对接收到的信号进行处理，根据其相位，幅度，频率，信噪比等的不同特征，从而分离出所有不希望得到的稳态噪声和非稳态噪声，从而实现去噪，生源定位和跟踪，语音提取和分离，进而提高嘈杂环境下的语音质量。本发明使用双MIC环境噪音消除技术，可消除噪音达30dB以上，也可以提供回音消除与单MIC噪音降低功能，使用者在嘈杂的环境下也可以得到清晰的语音通话或录制效果。
本发明还提供了一种内置上述音频降噪电路的智能终端机，其通过实时采集、录制教学者的音频信息，实现了教学音频数据实时录制，解决了学习内容预置智能终端机中，学习时相对单调，乏味，学习效果不佳的问题。
其中，为了解决上述问题，其采用如下技术方案：
一种智能终端机，包括：
一内设有上述音频降噪电路的主机及一与该主机连接的高拍仪。
进一步地，所述主机包括底壳和中框，底壳和中框之间固定安装有主板、液晶屏和触控屏，所述主板和液晶屏通过FPC连接器电性连接；所述底壳后端设置有一开口槽，中框后端设置有一容置槽，该容置槽对应位于所述开口槽中，且所述开口槽中还设置有一可翻转打开的翻转盖板，所述翻转盖板翻转后可与容置槽对应形成一密封腔；
所述高拍仪，设置于上述容置槽中，其包括有主支架、副支架和拍照杆，所述主支架一端通过转轴件与固定安装在容置槽中的连接件转动连接，另一端则通过第一垂直转轴与副支架一端活动连接，所述副支架可绕第一垂直转轴垂直于主支架打开或合拢；所述副支架的另一端通过一水平转轴和第二垂直转轴与拍照杆活动连接，所述拍照杆可绕第二垂直转轴垂直于副支架打开或合拢，且在拍照杆处于打开状态时绕水平转轴在水平方向翻转。
进一步地，所述主板上设置有电池、3G模块、SIM卡槽和包含音频降噪电路的主板电路，所述3G模块和SIM卡槽通过主板电路与电池连接。
进一步地，所述副支架包括副支架上盖、副支架下盖以及安装在副支架上 盖、副支架下盖之间的线路板，该线路板通过设置于主支架内的线路与主板电性连接。
进一步地，所述拍照杆包括拍照杆上盖、拍照杆下盖以及安装在拍照杆上盖、拍照杆下盖之间的摄像模块和麦克风，所述摄像模块与所述线路板电性连接，且所述摄像模块上设置有摄像头。
进一步地，所述主板上还设置有一用于插IC卡的IC卡插槽和一用于读取磁卡磁条信息的磁卡磁头，所述IC卡插槽和磁卡磁头均与主板电路连接。
进一步地，所述底壳后端还设置有一插孔，该插孔中固定有电磁笔。
进一步地，所述底壳后端底部设置有一后支撑垫，前端底部设置有一前支撑垫。
本发明所述的智能终端机采用了音频降噪电路，采用两个麦克风采集音频信号，一个安装在主机上，一个安装在拍照杆上，通过这两个麦克风先吸收周边声音，然后输入到音频降噪电路中采用音频算法分辨出离设备最近的声音，比如60CM-300CM的距离采集和分辨人声音波长，从而判断靠近距离的音频信号为用户的语音，从而起到降低噪音的效果。
另外，本发明还提供了一种教学系统及方法，其将上述智能终端机与网络相结合，实现了教与学的实时互动。
为实现上述目的，本发明采用以下技术方案：
一种基于网络的教学系统，包括：
至少两台所述的智能终端机，其中一台为教学终端，其他为学习终端；
一后台服务器，用于存储教学终端录制上传的课程信息，并通过录制课程的ID和时间戳与该课程信息进行匹配；
其中所述教学终端、学习终端及后台服务器之间通过网络连接；
所述教学终端用于对教师课程进行录制，并对应以数据流和音频流的方式上传保存在后台服务器中；
所述学习终端用于获取录制课程的ID，并对应从后台服务器中读取与时间 戳对应的数据流和音频流。
进一步地，所述教学终端、学习终端及后台服务器之间通过无线或有线网络通信连接。
进一步地，该系统还包括有一与所述教学终端通信连接的放映设备。
进一步地，所述数据流为教学终端在教师多媒体课堂中录制的讲课时间和动作信息；所述音频流为教学终端在教师多媒体课堂中录制的课堂时间和语音信息。
本发明还提供了一种基于网络的教学方法，包括步骤：
S1、通过教学终端录制教师课程，并对应以数据流和音频流的方式上传保存在后台服务器中；
S2、学习终端对应从后台服务器获取录制课程的ID，并对应从后台服务器中读取与时间戳对应的数据流和音频流。
进一步地，步骤S1之前包括：
建立教学终端、学习终端以及后台服务器之间的通信连接，所述通信连接包括有线网络连接以及WIFI、3G、4G无线网络连接。
进一步地，步骤S1中通过教学终端录制教师课程时，同时设置与该录制课程对应的ID。
进一步地，步骤S2之后还包括有：
学习终端通过后台服务器反馈信息到教学终端，教学终端针对该反馈信息对应进行解答，其中所述反馈信息包括学习终端建立的电子文本文档或通过高拍仪摄像头扫描的手写纸质文档。
进一步地，教学终端主动发起提问，要求指定学习终端进行回答，并在其回答结束后给予反馈；或者教学终端主动发起提问，学习终端进行反馈响应，且在教学终端做出选择后，被选择的学习终端进行回答，且在回答结束后教学终端给予反馈。
本发明教学系统及方法，可实现老师将每天的电子教案以及上课现场课件 实时上传，使外校学生或者学生家长能够随时随地观看，实现了优质师资力量的无线分享；本系统通过网络服务器对老师的教案及视屏资料进行上传保存，避免了因老师的离职或退休而造成知识的丢失；另外，本发明基于网络的教学方式，实现了老师、学生教与学的实时同步反馈，具有互动性强，学习效果好的优点。
附图说明
图1为本发明音频降噪处理芯片的电路原理图；
图2为本发明音频输入电路的电路原理图；
图3为本发明音频放大缓冲电路的电路原理图；
图4为本发明滤波电路的电路原理图；
图5为本发明功率放大电路的电路原理图；
图6为本发明智能终端机的使用状态示意图一；
图7为本发明智能终端机的使用状态示意图二；
图8为本发明智能终端机的使用状态示意图三；
图9为本发明智能终端机的结构示意图；
图10为本发明教学系统的网络连接原理图；
图11为本发明教学系统中教学端课程录制原理图；
图12为本发明教学系统中学习端课程回顾的原理图；
图13为本发明教学方法的实施流程图。
图中标识说明：主机1、底壳11、开口槽111、插孔112、前支撑垫113、支撑垫114、卡盖115、主板12、电池121、FPC连接器122、磁卡磁头123、IC卡插槽124、液晶屏13、中框14、触控屏15、容置槽2、翻转盖板3、主支架4、转轴件41、连接件42、副支架5、副支架上盖51、副支架下盖52、线路板53、第一垂直转轴54、拍照杆6、拍照杆上盖61、拍照杆下盖62、摄像模块63、摄像头631、第二垂直转轴64、水平转轴65、电磁笔7。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明提供了一种音频降噪电路，以针对传统教学中老师需要到专业的录音棚中录制音频视频，现场教学条件有限，音频录制效果噪音较大，不能进行同步录音教学的问题，
请参阅图1～图5所示，作为一种实施例，本发明包括有：音频输入电路、音频放大缓冲电路、音频降噪处理芯片、滤波电路和功率放大电路。
如图2所示，图2为本发明音频输入电路的电路原理图。本实施例中音频输入电路，包括有一个输入切换电路和两个麦克风(麦克风MIC1和麦克风MIC_CON1)。这两个麦克风用于采集包含有噪音的语音信号(分别为两路)，其中可选择任意一路作为背景噪音的检测信号，而另外一路则作为语音的检测信号，且所述的两个麦克风(麦克风MIC1、麦克风MIC_CON1)处于不同位置，且二者之间的距离为5～20CM。
输入切换电路包括有输入麦克风切换开关芯片U545，其对应采用SGM3157YC6芯片。麦克风MIC1与麦克风切换开关芯片U545的1号脚(JACK_MIC_0_NO)连接，以通过麦克风MIC1输入音频信号；麦克风MIC_CON1与麦克风切换开关芯片U545的3号脚(JACK_MIC_0_NC)连接，以通过麦克风MIC_CON1输入音频信号；麦克风切换开关芯片U545的3号脚(COM)为输出脚，其对应为JACK_MIC_0并连接到滤波电感L530后分为两路输出，一路对应到输出端MIC_0，另一路通过电阻R823、R822后对应到输出端MIC_BAISI；在电阻R823、R822之间还通过电容C877接地。
麦克风MIC1和麦克风MIC_CON1将采集到的包含有噪音的音频信号输入到输入切换电路，并通过麦克风切换开关芯片U545进行切换处理后从COM脚输出，且从COM脚输出的切换后音频信号经过滤波电感L530后到输出端MIC_0，并对应输入到音频放大缓冲电路。
如图3所示，图3为本发明音频放大缓冲电路的电路原理图。音频放大缓冲电路，包括有两部分，第一部分对麦克风MIC1输入的音频信号进行放大缓冲处理，第二部分对麦克风MIC_CON1输入的音频信号进行放大缓冲处理。
其中第一部分电路包括有电容C888、C889、C890、C891、C892、C893，运算放大器U544A，电阻R831、R832、R833、R834、R835和R836；运算放大器U544A为NJM2746V芯片，电容C888为隔直流电容，U544A的3号脚与电容C888连接，在电容C888与U544A的3号脚之间还连接有电阻R832，所述电阻R832的另一端分为两路，一路通过电容C890接地，另一路通过电阻R833接电；U544A的2号脚分为两路，一路通过电阻R834与U544A的1号脚连接，另一路则通过电阻R836、C891接地；U544A的1号脚通过电容C889、电阻R831到输出端XMIC_0。
麦克风切换开关芯片U545的COM脚输出的切换后音频信号经过滤波电感L530后，由输出端MIC_0经过隔直流电容C888后输入到运算放大器U544A的3号脚，经过运算放大器U544A的放大缓冲之后由运算放大器U544A的1号脚输出，再经过隔直流电容C889后到输出端XMIC_0。
第二部分电路包括有电容C895、C896、C897、C898、C899，运算放大器U544B，电阻R838、R839、R840、R841、R842、R843；运算放大器U544B为NJM2746V芯片，电容C895为隔直流电容，U544B的5号脚与电容C895连接，在电容C895与U544B的5号脚之间还连接有电阻R839，所述电阻R839的另一端分为两路，一路通过电容C898接地，另一路通过电阻R840接电；U544B的6号脚分为两路，一路通过电阻R841与U544B的7号脚连接，另一路则通过电阻R843、C899接地；U544B的7号脚通过电容C896、电阻R838到输出端XMIC_1。
第二部分电路的输入端MIC_1通过测试点TP24连接到麦克风切换开关芯片U545的JACK_MIC_0_NC脚，而输入端MIC_1经过隔直流电容C895后输入到运算放大器U544B的5号脚，经过运算放大器U544B的放大缓冲之后由 运算放大器U544B的7号脚输出，再经过隔直流电容C896后到输出端XMIC_1，并输入到音频降噪处理芯片。
如图1所示，图1为本发明音频降噪处理芯片的电路原理图。上述音频输入电路和音频放大缓冲电路均为音频降噪处理芯片的外围电路，其中音频降噪处理芯片为CM6571芯片，CM6571作为一颗自动回音消除的处理核心，采用语音处理技术，应用在语音和音乐等通讯方面，能有效降低环境噪音(ENC)，具备远距离智能语音捕获(SVC)，语音强化(HD VOICE)，背景噪音消除(AEC)，远距离录音(LDR)等功能。
其中音频降噪处理芯片包括有时钟接口、USB接口、电源接地接口、音频接口、双通道I2S DAC接口、双通道I2S接口、数字麦克风接口、双通道I2S ADC接口、S/PDIF I/O接口、可编程IO部分、主串行总线接口和设置引脚部分。
上述时钟接口包括有12MHz晶体输入脚XTAL_I、12MHz晶体输出脚XTAL_O和时钟输入脚D_CLK_IN。USB接口包括有USB_DM脚和USB_DP脚，均为USB2.0数据接口，其中通过该USB接口可以与CPU连接，所述CPU对应为与CM6571进行数据通信的中央处理器芯片。电源接地接口包括有5V数字电路电源DV50、1.8V电源VCC18IO、+3.3V输出XV33、数字地GND18IO/GND3IO、5V模拟电源AV50、模拟地AGND、+3.5V供电电压XV35_DAC、+3.5V参考电压XV35_ADC、+3.5V驱动电压XV35_DRIVER、接滤波电容D_XV24_DA、模拟地D_AGND、模拟电源D_AVDD、参考电压，电容接地D_XVREF、数字电源D_DVDD、PLL电源，电容接地D_XV1.2、数字地D_DGND。音频接口包括有共模输入信号参考脚XACREFL/XACREFR、左通道麦克风输入脚XMICL、右通道麦克风输入脚XMICR、模拟麦克风1差分输入脚D_MIC1_N、模拟麦克风0差分输入脚D_MIC0_N、模拟麦克风1差分输入脚D_MIC1_P、模拟麦克风0差分输入脚D_MIC0_P、左通道线路输入脚XLINL、右通道线路输入脚XLINR、麦克风基准电压2.75V脚XMICBIAS2及XMICBIAS1、参考电压电容接地脚XVAG、控制模拟电压输出脚XVOLADJ、 左通道线路输出脚XLNOUTL、无电容线路输出脚XLOCOM、右通道线路输出脚XLNOUTR、辅助差分输入P脚D_AUXIN_P、辅助差分输入N脚D_AUXIN_N。双通道I2S DAC接口包括有I2S主时钟脚DAC_MCLK、I2S位时钟脚DAC_BCLK、I2S串行数据脚DAC_DOUT、I2S左/右时钟脚DAC_LRCK、数据输入脚DAC_DIN。双通道I2S接口包括有I2S位时钟D_I2S_BCLK、I2S数据输入D_I2S_DI、I2S左/右时钟D_I2S_LRCK、2S串行数据D_I2S_DO。数字麦克风接口包括有数字麦克风时钟输入脚D_DMO_CLK、数字麦克风时钟输出脚D_DMI_CLK、数字麦克风数据输入脚D_DMI_DAT、数字麦克风数据输出脚D_DMO_DAT。双通道I2S ADC接口包括有模数转换数据输出脚ADC_DOUT、I2S左/右时钟脚ADC_LRCK、I2S串行数据输入脚ADC_DIN、I2S位时钟脚ADC_BCLK、I2S主时钟脚ADC_MCLK。S/PDIF I/O接口包括有S/PDIF发送脚SPDIF_O；可编程IO部分包括有通用可编程I/O脚GPIO_10～GPIO_18；主串行总线接口包括有2线主串行数据脚I2C_SDAT_0、2线串行时钟脚I2C_SCLK_0、I2C时钟脚D_I2C_CLK_1、I2C数据脚D_I2C_DAT_1；设置引脚包括有关机状态脚PDSW、测试脚TEST_0、测试脚D_TEST_1、工作模式选择脚D_MSEL_0、复位引脚D_RSTN。
其中经过音频放大缓冲电路放大缓冲之后的麦克风MIC1音频信号经过输出端XMIC_0后输入到左通道麦克风输入脚XMICL；经过音频放大缓冲电路放大缓冲之后的麦克风MIC_CON1音频信号经过输出端XMIC_1后输入到右通道麦克风输入脚XMICR；音频降噪处理芯片对输入的两路音频信号通过模拟麦克风和数字麦克风接口阵列消除噪音，并通过ICA算法进行盲源分析，分离出稳态噪声和非稳态噪声，进行语音提取和分离，并将提取和分离的语音信号经过音频降噪处理芯片的左通道线路输出脚XLNOUTL、右通道线路输出脚XLNOUTR输出到滤波电路。
其中本发明中采用的音频降噪处理芯片CM6571采用双麦克风阵列消除噪音，利用ICA算法进行盲源分析，麦克风MIC1、麦克风MIC_CON1这两个麦 克风收到的远场噪声幅度是基本一样的，而对近场声源，收到的幅度就相差很大，通过算法分离就可以得到比较好的效果。另外噪声分为稳态噪声和非稳态噪声，对于稳态噪声，在频域上进行功率谱的叠加，然后滤波来消除，对于非稳态噪声，不同位置上的两个麦克风，对接收到的信号进行处理，通过其相位，幅度，频率，信噪比等的不同特征，分离出所有不希望得到的稳态噪声和非稳态噪声，就可以实现去噪，生源定位和跟踪，语音提取和分离，从而提高嘈杂环境下的语音质量。
如图4所示，图4为本发明滤波电路的电路原理图。其中该滤波电路包括有输入端LOUT_L_OUT、LOUT_R_OUT，滤波电感L546、L547，隔直流电容C942、C943、C944、C945，电阻R923、R924。输入端LOUT_L_OUT与滤波电感L546之间连接有隔直流电容C943，所述隔直流电容C943接地；滤波电感L546与C944连接，且在二者之间连接有电阻R924，通过电阻R924接地；输入端LOUT_R_OUT与滤波电感L547之间连接有隔直流电容C942，且该隔直流电容C942接地；滤波电感L547与C945连接，且在二者之间连接有电阻R923，通过电阻R923接地。
经过音频降噪处理芯片降噪处理后，提取和分离的语音信号经过左通道线路输出脚XLNOUTL，由输入端LOUT_L_OUT输入到滤波电感L546进行滤波处理后，再经过隔直流电容C944由LOUT_L端输出；经过音频降噪处理芯片降噪处理后，提取和分离的语音信号经过右通道线路输出脚XLNOUTR，由输入端LOUT_R_OUT输入到滤波电感L547进行滤波处理后，再经过隔直流电容C945由LOUT_R端输出。
如图5所示，图5为本发明功率放大电路的电路原理图。其中本实施例功率放大电路，包括隔直流电容C875、C876、C879、C880、C881、C882、C883、C884、C886，功率放大芯片U543，滤波电感L531、L533、L534、L535、L536，电阻R819、R820、R823、R826，功率放大芯片U543为NS4251芯片。隔直流电容C875通过电阻R820与功率放大芯片U543的8号脚INNA连接，U543 的电源脚VDD1、VDD2通过L534连接到VDDSW，且VDD1、VDD2还通过C881、C882接地；U543的VREF脚通过C883接地，HP-IN脚与电阻R823连接；隔直流电容C876通过电阻R826与功率放大芯片U543的13号脚INNB连接。
功率放大芯片U543的VONA脚和VOPA脚构成一组输出信号到喇叭，其中VONA脚通过滤波电感L531输出到喇叭，且在滤波电感L531与喇叭之间连接有电容C879，该电容C879接地；U543的VOPA脚通过滤波电感L533输出到喇叭，且在滤波电感L533与喇叭之间连接有电容C880，该电容C880接地。其中经过滤波电路滤波后由LOUT_L端输出的语音信号经过隔直流电容C875后输入到功率放大芯片U543，经过功率放大芯片U543放大后为一组音频信号分别经过滤波电感L531、L533后输出到喇叭。
功率放大芯片U543的VONB脚和VOPB脚构成另外一组输出信号到喇叭，其中VONB脚通过滤波电感L535输出到喇叭，且在滤波电感L535与喇叭之间连接有电容C884，该电容C884接地；U543的VOPB脚通过滤波电感L536输出到喇叭，且在滤波电感L536与喇叭之间连接有电容C886，该电容C886接地。经过滤波电路滤波后由LOUT_R端输出的语音信号经过隔直流电容C876后输入到功率放大芯片U543，经过功率放大芯片U543放大后为另一组音频信号分别经过滤波电感L535、L536输出到喇叭。
由于通常情况下用户的正常语音频率为2～20Khz，而超出或低于该范围的音频信号均可视为环境噪音。本电路通过使用双MIC环境噪音消除技术，可消除噪音达30dB以上，也可以提供回音消除与单MIC噪音降低功能，使用者在嘈杂的环境下也可以得到清晰的语音通话或录制效果。
以上是对本发明音频降噪电路的说明，下面将结合附图6～9对采用上述音频降噪电路的一种智能终端机进行说明。
本发明还提供了一种智能终端机，其主要用于教育领域，其主要针对目前教学用智能终端设备存在音频信息环境噪音多、音频质量不高，学习不能实现 实时同步反馈，互动性差，学习效果不好的问题。
本发明针对现有技术进行了改进，主要包括有主机1和高拍仪。
其中所述主机1包括有底壳11和中框14，底壳11和中框14之间固定安装有主板12、液晶屏13和触控屏15，所述主板12上设置有主板电路，该主板电路包括有上述音频降噪电路和CPU芯片，所述CPU与所述音频降噪电路中CM6571芯片通过USB接口连接。所述触控屏15为电容电磁复合式双层触摸屏，上层为电容屏，下层为电磁屏。
主板12上还设置有电池121、3G模块、SIM卡槽、IC卡插槽124和磁卡磁头123，所述3G模块、SIM卡槽、IC卡插槽124和磁卡磁头123均与主板电路连接，主板电路与电池121连接，通过电池121供电；磁卡磁头123用于读取磁卡磁条信息，IC卡插槽124用于插IC卡，读取IC卡信息。本发明通过IC卡插槽和磁卡磁头可实现银行卡的刷卡，便于教学培训机构的现场缴费，同时也可通过发放会员卡，实现刷卡签到、会员管理目的。
主板12上设置有FPC连接器122，通过该FPC连接器122可与液晶屏13连接。
底壳11后端设置有一个开口槽111，中框14的后端设置有一个容置槽2，该容置槽2对应位于所述开口槽111中，且在所述开口槽111中还设置有一个可翻转打开的翻转盖板3，所述翻转盖板3翻转后可与容置槽2对应形成一个密封腔。底壳11的后端还设置有一个插孔112，该插孔112中可对应固定电磁笔7，该电磁笔7内置有控制电路、电磁笔感应模块和供电电池，所述控制电路与电磁笔感应模块及供电电池电连接，一端为电磁笔尖，另一端激光笔端，电磁笔中部设有降噪话筒，降噪话筒连接控制电路，所述控制电路设有蓝牙模块，用于传输声音信号，该电磁笔不仅可以直接在触摸屏上书写，同时拿在手里可充当话筒和激光遥控器使用。
在底壳11的底部还设置有一个用于固定3G模块的卡盖115，另外为了达到较好的视角，在底壳11后端底部设置有一个后支撑垫114，前端底部设置有 一个前支撑垫113，以使整个主机1处于一定倾斜角度，方便用户观看使用。
高拍仪，设置于上述容置槽2中，其包括有主支架4、副支架5和拍照杆6，所述主支架4一端通过转轴件41与固定安装在容置槽2中的连接件42转动连接，另一端则通过第一垂直转轴54与副支架5一端活动连接。
副支架5包括副支架上盖51、副支架下盖52以及安装在副支架上盖51、副支架下盖52之间的线路板53，该线路板53通过设置于主支架4内的线路与主板12上的主板电路连接。
拍照杆6包括拍照杆上盖61、拍照杆下盖62以及安装在拍照杆上盖61、拍照杆下盖62之间的摄像模块63和麦克风，所述摄像模块63与所述线路板53电性连接，且所述摄像模块63上设置有摄像头631。
由于副支架5的一端通过第一垂直转轴54与主支架4活动连接。副支架5可绕第一垂直转轴54垂直于主支架4打开或合拢，当打开时，副支架5与主支架4垂直，且副支架5可绕第一垂直转轴54在水平面内旋转；当合拢时，副支架5与主支架4重叠(见图6、图7)。
副支架5的另一端通过一个水平转轴65和第二垂直转轴64与拍照杆6活动连接，拍照杆6可绕第二垂直转轴64垂直于副支架5打开或合拢，当打开时，拍照杆6可与副支架5打开至同一水平位置，二者处于同一水平线上；当合拢时，副支架5与拍照杆6对应重叠(见图6、图7)。
拍照杆6与副支架5之间还安装有一个水平转轴65，当拍照杆6相对于副支架5打开时，二者处于同一水平线上，此时在垂直方向上转动拍照杆6，拍照杆6可绕水平转轴65转动，对应将拍照杆6上安装有摄像头631和麦克风的一端朝向用户(见图8)。
当副支架5、主支架4以及拍照杆6三者处于合拢状态时，副支架5和拍照杆6与主支架4对应重叠，此时转动主支架4，其绕转轴件41转动，可对应容置于容置槽2中，对应将翻转盖板3转动到闭合状态，此时从外部看，本发明智能终端机为一个平板电脑。
当翻转盖板3处于打开状态时，可将高拍仪从容置槽2中取出，并对应按照如图6～8所示的方式将其打开至需要工作的状态。
另外，本发明可通过设置的电磁笔7对整个智能终端机进行操作，以实现教学。通过电磁笔可以极大方便老师与学生在线互动，老师的白板可以远程广播给学生；而采用的高拍仪可以方便老师为学生实时答疑，学生不清楚的题目可以直接通过高拍仪拍照上传，同时也方便了师生的在线互动。
本发明所述的智能终端机采用了音频降噪电路，采用两个麦克风采集音频信号，一个安装在主机上，一个安装在拍照杆上，通过这两个麦克风先吸收周边声音，然后输入到音频降噪电路中采用音频算法分辨出离设备最近的声音，比如60CM-300CM的距离采集和分辨人声音波长，从而判断靠近距离的音频信号为用户的语音，从而起到降低噪音的效果。
比如以直径3米为基础，采集3米内的声音，加以处理就可以分辨出人的声音波长，最后处理收集到设备里，而3米外的声音则以杂音处理掉。
以上是对本发明采用了音频降噪电路的智能终端机的说明，下面将结合附图10～12对采用该智能终端机通过网络的教学系统进行说明。
该教学系统主要包括有至少两台智能终端机，其中一台为教学终端，其他为学习终端。其中所述智能终端机采用IMX6主板，IMX6主板内置Android系统和系统优化单元，系统优化单元可对Bootloader、Linux kernel、Android Init进程启动和Android Server服务启动进行优化，其集成有包括由拾音器、AEC回音消除模块、音频放大器、外接扬声器或耳机组成的音频单元；由高拍仪摄像头、视频编解码器组成的视频单元；由触摸屏、电磁笔、LINE-IN接口、USB接口组成的输入单元；由触摸屏、HDMI接口组成的显示单元；由闪存、储存器、TFT卡插槽组成的存储单元；由磁条读写、IC读写、数据解码及加密处理芯片组成的刷卡单元以及由RJ45接口、WIFI模块、3G PCI-E模块组成的通信单元。
本发明教学系统还包括有一后台服务器，通过该后台服务器可存储教学终 端录制上传的课程信息，并通过录制课程的ID和时间戳与该课程信息进行匹配。所述后台服务器上部署有CentOS6.4或以上系统，使用Mysql数据库，用于智能终端机互动数据包括音频、视频和文本文件的存储，形成目录和索引，用于读取及调用，还储存系统运行产生的包括事件信息、登录信息、日志信息，用于课件编辑管理系统对课件的上传、管理。
其中所述教学终端、学习终端及后台服务器之间通过网络连接，三者之间可通过RJ45接口实现有线通信，或通过WIFI模块、3G PCI-E模块及4G模块等实现无线网络通信。所述教学终端用于对教师课程进行录制，并对应以数据流和音频流的方式上传保存在后台服务器中；所述学习终端用于获取录制课程的ID，并对应从后台服务器中读取与时间戳对应的数据流和音频流。所述数据流为教学终端在教师多媒体课堂中录制的讲课时间和动作信息；所述音频流为教学终端在教师多媒体课堂中录制的课堂时间和语音信息。
另外，该系统还包括有一台与所述教学终端通信连接的放映设备。所述放映设备采用投影仪和屏幕或者是宽屏显示器，用于课堂教学时，教师控制终端机通过HDMI接口连接所述放映设备，将终端机的触摸屏内容放映出来。
本系统还包括有教师PC端，教师通过PC端课登录所述的后台服务器，下载安装课件编辑器，该编辑器源码采用C&C++方式进行开发，基于Office2010Word版本进行多选题、单选题、判断题的添加和编辑，然后上传至后台服务器，形成试题课件和课件解析结果以XML文档保存在服务器；所述智能终端机利用课件解析的信息对课件进行分割并生成SWF题目文件，在触摸屏上进行显示，而答案的智能评判则是学生做完后的答案和服务器端预存的答案进行比对，在答题结束后可自动进行成绩统计，以方便随堂练习或测试。
本发明智能终端机包含有3G PCI-E模块，该模块中对应插入有SIM卡，本系统可将学生使用的学习终端SIM卡通信号码与该学生家长的手机号码相互绑定，而学生端使用家长姓名及手机号码在服务器注册个人档案账号，家长通过自己的姓名及手机号码可登陆服务器，通过将服务器与家长登陆信息相对比， 可实现登陆该学生个人档案账号，以使家长能够随时了解该学生在校上课情况及成绩轨迹。
本系统摆脱了由固定课室、讲台、教案、课本、黑板、粉笔等组成的传统教学系统及方式，实现现代化的互联网互动式的教学方式，摆脱了时空的限制，通过数据库储存电子课本，实现减轻了携带沉重的教材课本的负担，提高了教学效率，互动性和趣味性。本发明的智能终端机设计轻便、小巧方便携带，有效地解决了现有电教室教学系统，原有台式电脑机柜笨重、占用空间大、设备多、布线复杂、操作不便、排除故障难的问题。本发明设有HDMI接口连接放映设备和触摸屏的设计，实现电磁笔直接在触摸屏上编写，替代电脑输入键盘和黑板的书写，操作更为方便快捷，有利于提高教学质量和效率。本发明通过3G PCI-E模块插入SIM卡，实现连接3G移动网络，通过移动运营商可实现与家长智能手机终端进行绑定，通过登录服务器学生个人档案账号，查看老师后台上传至服务器数据库里的学生成绩统计及作业上课情况，实现随时随地了解子女在学校的学习情况。
以上是对本发明智能终端机网络教学系统的描述，下面将结合附图13对采用智能终端机进行网络教学方法做进一步描述，其中本发明基于网络的教学方法，包括有如下步骤：
首先建立教学终端、学习终端以及后台服务器之间的通信连接，所述通信连接包括有线网络连接以及WIFI、3G、4G无线网络连接。
接着通过教学终端录制教师课程，并对应以数据流和音频流的方式上传保存在后台服务器中；其中通过教学终端录制教师课程时，需要同时设置与该录制课程对应的ID。
然后学习终端对应从后台服务器获取录制课程的ID，并对应从后台服务器中读取与时间戳对应的数据流和音频流。
学习终端通过后台服务器反馈信息到教学终端，教学终端针对该反馈信息对应进行解答，其中所述反馈信息包括学习终端建立的电子文本文档或通过高 拍仪摄像头扫描的手写纸质文档。教学终端主动发起提问，要求指定学习终端进行回答，并在其回答结束后给予反馈；或者教学终端主动发起提问，学习终端进行反馈响应，且在教学终端做出选择后，被选择的学习终端进行回答，且在回答结束后教学终端给予反馈。
本发明智能终端机可基于互联网开发课前备课、课堂教学、课后辅导和远程教育等应用。课前备课，教师通过带有Android操作系统的智能终端机进行备课，启动智能终端机，按需求建立Word、PPT文档编辑课件，或者通过高拍仪摄像头扫描手写纸质教案；课堂教学，教师使用教学终端机，学生使用学习终端机，教学终端机和学习终端机之间通过WIFI模块或RJ45连接网线建立网络连接，其采用TCP/IP多播协议实现主从控制，所有子控制终端机同步显示主控制终端机界面，实现多屏同步授课；课堂授课步骤可云端同步接入学习终端机，学习终端机通过所述通信单元连接互联网，实现与所述后台服务器网络连接，通过网络登录远程教育应用单元，对课程进行预约，通过教师端的教学终端机确认，实现远程同步接收教师教学终端机通过高拍仪摄像头、拾音器采集的视频和音频信号，和触摸屏内容同步到服务器数据库，从而实现学习终端机同步学习或后续回顾学习的目的；互动交流，通过教学终端机解除多屏同步，所有学习终端机为独立个体，学习终端机之间仍可进行网络连接，将学生分为若干讨论组进行互动，随堂作业的自由交流讨论；实时问答，学生通过电子举手按键，教学终端机接收有意愿回答问题的学生座位列表，教师选择学生回答，通过教学终端机授权所有其他学习终端机同步显示该学习终端机的界面，如果回答错误，教师返回有意愿回答问题的学生座位列表，重新选择学生回答，如果回答正确，则进入下一个问题。
对于学习终端而言，学生可启动终端机，并登录服务器下载教师上传到服务器的作业文档；并直接在触摸显示屏手写输入答案内容，或者在纸质作业本上书写，然后通过高拍仪摄像头扫描形成文档上传至服务器。其具体使用方式如下：首先教师和学生使用各自的终端机用个人身份信息通过网络在后台服务 器注册，该注册信息与数据库储存的信息进行匹配完成后，才能确认注册完成；之后学生登录网络进入到后台服务器中的互动答疑应用单元，并通过触摸屏编写问题或通过高拍仪扫描书写的问题，完成问题文件上传至后台服务器，之后则在互动答疑应用单元查看教师列表，并点击查看教师详情，然后选择教师进行求解；而教师则使用教学终端，登录后台服务器中的互动答疑单元模块，查看待答问题列表，然后选择问题，使用触摸屏、电磁笔编写或高拍仪扫描等方式书写文本，或采用高拍仪录制解答的音、视频文件，完成答案上传；最后学生则查看已回答的问题列表，下载并查看问题的详情及回放答案。
综上所述，本发明通过对教师在线课堂的多媒体(分题多媒体白板讲解、答题智能成绩统计、课后音频讨论及发言等)讲课、课堂发言音频系统进行实时录制，学生通过远程试题辅导系统或在线讲课系统的课堂回顾功能，实现了对录制课程的点播回顾。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (22)

  1. 一种音频降噪电路，其特征在于，包括：音频输入电路、音频放大缓冲电路、音频降噪处理芯片、滤波电路和功率放大电路。
  2. 如权利要求1所述的音频降噪电路，其特征在于，包括：
    音频输入电路，包括有麦克风MIC1、麦克风MIC_CON1和输入切换电路，所述输入切换电路包括有输入麦克风切换开关芯片U545；所述麦克风MIC1与麦克风切换开关芯片U545的JACK_MIC_0_NO脚连接，麦克风MIC_CON1与麦克风切换开关芯片U545的JACK_MIC_0_NC脚连接，麦克风MIC1和麦克风MIC_CON1用于将采集到的包含有噪音的音频信号输入到输入切换电路，并通过麦克风切换开关芯片U545进行切换处理后从COM脚输出，且从COM脚输出的切换后音频信号经过滤波电感L530后到输出端MIC_0；
    音频放大缓冲电路，包括有对麦克风MIC1和麦克风MIC_CON1输入的音频信号分别进行放大缓冲的电路，其中对麦克风MIC1输入音频信号进行放大缓冲的电路包括有电容C888、C889、C890、C891、C892、C893，运算放大器U544A，电阻R831、R832、R833、R834、R835和R836；麦克风切换开关芯片U545的COM脚输出的切换后音频信号经过滤波电感L530后，由输出端MIC_0经过隔直流电容C888后输入到运算放大器U544A的3号脚，经过运算放大器U544A的放大缓冲之后由运算放大器U544A的1号脚输出，再经过隔直流电容C889后到输出端XMIC_0；对麦克风MIC_CON1输入音频信号进行放大缓冲的电路包括有电容C895、C896、C897、C898、C899，运算放大器U544B，电阻R838、R839、R840、R841、R842、R843；输入端MIC_1通过测试点TP24连接到麦克风切换开关芯片U545的JACK_MIC_0_NC脚，而输入端MIC_1经过隔直流电容C895后输入到运算放大器U544B的5号脚，经过运算放大器U544B的放大缓冲之后由运算放大器U544B的7号脚输出，再经过隔直流电容C896后到输出端XMIC_1；
    音频降噪处理芯片，包括有时钟接口、USB接口、音频接口、双通道I2SDAC接口、双通道I2S接口、数字麦克风接口和双通道I2S ADC接口；所述时钟接口包括有12MHz晶体输入脚XTAL_I、12MHz晶体输出脚XTAL_O和时钟输入脚D_CLK_IN；所述USB接口包括有USB_DM脚和USB_DP脚；所述音频接口包括有共模输入信号参考脚XACREFL/XACREFR、左通道麦克风输入脚XMICL、右通道麦克风输入脚XMICR、模拟麦克风1差分输入脚D_MIC1_N、模拟麦克风0差分输入脚D_MIC0_N、模拟麦克风1差分输入脚D_MIC1_P、模拟麦克风0差分输入脚D_MIC0P；所述双通道I2S DAC接口包括有I2S主时钟脚DAC_MCLK、I2S位时钟脚DAC_BCLK、I2S串行数据脚DAC_DOUT、I2S左/右时钟脚DAC_LRCK、数据输入脚DAC_DIN；所述双通道I2S接口包括有I2S位时钟D_I2S_BCLK、I2S数据输入D_I2S_DI、I2S左/右时钟D_I2S_LRCK、2S串行数据D_I2S_DO；所述数字麦克风接口包括有数字麦克风时钟输入脚D_DMO_CLK、数字麦克风时钟输出脚D_DMI_CLK、数字麦克风数据输入脚D_DMI_DAT、数字麦克风数据输出脚D_DMO_DAT；所述双通道I2S ADC接口包括有模数转换数据输出脚ADC_DOUT、I2S左/右时钟脚ADC_LRCK、I2S串行数据输入脚ADC_DIN、I2S位时钟脚ADC_BCLK、I2S主时钟脚ADC_MCLK；其中经过音频放大缓冲电路放大缓冲之后的麦克风MIC1音频信号经过输出端XMIC_0后输入到左通道麦克风输入脚XMICL；经过音频放大缓冲电路放大缓冲之后的麦克风MIC_CON1音频信号经过输出端XMIC_1后输入到右通道麦克风输入脚XMICR；音频降噪处理芯片对输入的两路音频信号通过模拟麦克风和数字麦克风接口阵列消除噪音，并通过ICA算法进行盲源分析，分离出稳态噪声和非稳态噪声，进行语音提取和分离，并将提取和分离的语音信号经过音频降噪处理芯片的左通道线路输出脚XLNOUTL、右通道线路输出脚XLNOUTR输出；
    滤波电路，包括输入端LOUT_L_OUT、LOUT_R_OUT，滤波电感L546、L547，隔直流电容C944、C945；经过音频降噪处理芯片降噪处理后，提取和 分离的语音信号经过左通道线路输出脚XLNOUTL，由输入端LOUT_L_OUT输入到滤波电感L546进行滤波处理后，再经过隔直流电容C944由LOUT_L端输出；经过音频降噪处理芯片降噪处理后，提取和分离的语音信号经过右通道线路输出脚XLNOUTR，由输入端LOUT_R_OUT输入到滤波电感L547进行滤波处理后，再经过隔直流电容C945由LOUT_R端输出；
    功率放大电路，包括隔直流电容C875、C876，功率放大芯片U543，滤波电感L531、L533、L535、L536，经过滤波电路滤波后由LOUT_L端输出的语音信号经过隔直流电容C875后输入到功率放大芯片U543，经过功率放大芯片U543放大后为一组分别经过滤波电感L531、L533输出到喇叭；经过滤波电路滤波后由LOUT_R端输出的语音信号经过隔直流电容C876后输入到功率放大芯片U543，经过功率放大芯片U543放大后为一组分别经过滤波电感L535、L536输出到喇叭。
  3. 如权利要求2所述的音频降噪电路，其特征在于，所述麦克风MIC1、麦克风MIC_CON1输入的语音信号中任意一路作为背景噪音的检测信号，另外一路作为语音的检测信号，且所述麦克风MIC1、麦克风MIC_CON1处于距离为5～20CM的不同位置。
  4. 如权利要求2所述的音频降噪电路，其特征在于，所述音频降噪处理芯片为CM6571芯片；麦克风切换开关芯片U545为SGM3157YC6芯片；运算放大器U544A、U544B均为NJM2746V芯片、功率放大芯片U543为NS4251芯片。
  5. 如权利要求2所述的音频降噪电路，其特征在于，所述音频输入电路通过音频降噪处理芯片CM6571的USB接口USB_DM和USB_DP与CPU连接。
  6. 一种智能终端机，其特征在于，包括：
    一内设有如权利要求1～4所述的音频降噪电路的主机(1)及一与该主机(1)连接的高拍仪。
  7. 如权利要求6所述的智能终端机，其特征在于，
    所述主机(1)包括底壳(11)和中框(14)，底壳(11)和中框(14)之间固定安装有主板(12)、液晶屏(13)和触控屏(15)，所述主板(12)和液晶屏(13)通过FPC连接器(122)电性连接；所述底壳(11)后端设置有一开口槽(111)，中框(14)后端设置有一容置槽(2)，该容置槽(2)对应位于所述开口槽(111)中，且所述开口槽(111)中还设置有一可翻转打开的翻转盖板(3)，所述翻转盖板(3)翻转后可与容置槽(2)对应形成一密封腔；
    所述高拍仪，设置于上述容置槽(2)中，其包括有主支架(4)、副支架(5)和拍照杆(6)，所述主支架(4)一端通过转轴件(41)与固定安装在容置槽(2)中的连接件(42)转动连接，另一端则通过第一垂直转轴(54)与副支架(5)一端活动连接，所述副支架(5)可绕第一垂直转轴(54)垂直于主支架(4)打开或合拢；所述副支架(5)的另一端通过一水平转轴(65)和第二垂直转轴(64)与拍照杆(6)活动连接，所述拍照杆(6)可绕第二垂直转轴(64)垂直于副支架(5)打开或合拢，且在拍照杆(6)处于打开状态时绕水平转轴(65)在水平方向翻转。
  8. 如权利要求7所述的智能终端机，其特征在于，所述主板(12)上设置有电池(121)、3G模块、SIM卡槽和包含音频降噪电路的主板电路，所述3G模块和SIM卡槽通过主板电路与电池(121)连接。
  9. 如权利要求8所述的智能终端机，其特征在于，所述副支架(5)包括副支架上盖(51)、副支架下盖(52)以及安装在副支架上盖(51)、副支架下盖(52)之间的线路板(53)，该线路板(53)通过设置于主支架(4)内的线路与主板(12)电性连接。
  10. 如权利要求9所述的智能终端机，其特征在于，所述拍照杆(6)包括拍照杆上盖(61)、拍照杆下盖(62)以及安装在拍照杆上盖(61)、拍照杆下盖(62)之间的摄像模块(63)和麦克风，所述摄像模块(63)与所述线路板(53)电性连接，且所述摄像模块(63)上设置有摄像头(631)。
  11. 如权利要求10所述的智能终端机，其特征在于，所述主板(12)上还 设置有一用于插IC卡的IC卡插槽(124)和一用于读取磁卡磁条信息的磁卡磁头(123)，所述IC卡插槽(124)和磁卡磁头(123)均与主板电路连接。
  12. 如权利要求11所述的智能终端机，其特征在于，所述底壳(11)后端还设置有一插孔(112)，该插孔(112)中固定有电磁笔(7)。
  13. 如权利要求12所述的智能终端机，其特征在于，所述底壳(11)后端底部设置有一后支撑垫(114)，前端底部设置有一前支撑垫(113)。
  14. 一种基于网络的教学系统，其特征在于，包括：
    至少两台如权利要求6～13所述的智能终端机，其中一台为教学终端，其他为学习终端；
    一后台服务器，用于存储教学终端录制上传的课程信息，并通过录制课程的ID和时间戳与该课程信息进行匹配；
    其中所述教学终端、学习终端及后台服务器之间通过网络连接；
    所述教学终端用于对教师课程进行录制，并对应以数据流和音频流的方式上传保存在后台服务器中；
    所述学习终端用于获取录制课程的ID，并对应从后台服务器中读取与时间戳对应的数据流和音频流。
  15. 如权利要求14所述的基于网络的教学系统，其特征在于，所述教学终端、学习终端及后台服务器之间通过无线或有线网络通信连接。
  16. 如权利要求14所述的基于网络的教学系统，其特征在于，还包括有一与所述教学终端通信连接的放映设备。
  17. 如权利要求14所述的基于网络的教学系统，其特征在于，所述数据流为教学终端在教师多媒体课堂中录制的讲课时间和动作信息；所述音频流为教学终端在教师多媒体课堂中录制的课堂时间和语音信息。
  18. 一种基于网络的教学方法，其特征在于，包括步骤：
    S1、通过教学终端录制教师课程，并对应以数据流和音频流的方式上传保存在后台服务器中；
    S2、学习终端对应从后台服务器获取录制课程的ID，并对应从后台服务器中读取与时间戳对应的数据流和音频流。
  19. 如权利要求18所述的基于网络的教学方法，其特征在于，步骤S1之前包括：
    建立教学终端、学习终端以及后台服务器之间的通信连接，所述通信连接包括有线网络连接以及WIFI、3G、4G无线网络连接。
  20. 如权利要求18所述的基于网络的教学方法，其特征在于，步骤S1中通过教学终端录制教师课程时，同时设置与该录制课程对应的ID。
  21. 如权利要求18所述的基于网络的教学方法，其特征在于，步骤S2之后还包括有：
    学习终端通过后台服务器反馈信息到教学终端，教学终端针对该反馈信息对应进行解答，其中所述反馈信息包括学习终端建立的电子文本文档或通过高拍仪摄像头扫描的手写纸质文档。
  22. 如权利要求18所述的基于网络的教学方法，其特征在于，教学终端主动发起提问，要求指定学习终端进行回答，并在其回答结束后给予反馈；或者教学终端主动发起提问，学习终端进行反馈响应，且在教学终端做出选择后，被选择的学习终端进行回答，且在回答结束后教学终端给予反馈。
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