A loudspeaker online monitoring system and public address system

Abstract

The application provides a kind of loudspeaker online monitoring system and public broadcast system, the system includes: host computer, detection control device, power amplifier, and the detection terminal of matching setting with loudspeaker;The first end of detection control device is connected with the input end of power amplifier;The second end of detection control device and the output end of power amplifier are connected with the input end of each detection terminal;Detection control device is used to mix audio signal with ultrasonic signal, and sends mixed signal to power amplifier;Power amplifier is used to amplify the mixed signal received, and sends mixed amplified signal to each detection terminal;Detection terminal is used to sample power amplifier circuit and loudspeaker loop, when power amplifier circuit sampling voltage and loudspeaker loop sampling current include ultrasonic data and ultrasonic data is within the preset voltage range, it is determined that power amplifier circuit and loudspeaker loop work normally;The application can realize one-to-one detection of loudspeaker while improving the detection accuracy of loudspeaker working state.

Description

Technical Field

[0001] This invention relates to the field of intelligent monitoring and control system technology, and in particular to an online loudspeaker monitoring system and a public address system. Background Technology

[0002] A loudspeaker is an electroacoustic transducer that converts electrical signals into sound signals. A public address system is an audio transmission system specifically designed for large areas, primarily used to disperse a large number of loudspeakers in public places (such as shopping malls, schools, and airports) to meet sound reinforcement needs. This system transmits audio signals to each loudspeaker through a transmission network, achieving uniform sound coverage and clear transmission. In a public address system, the loudspeaker, as the terminal device, is responsible for converting the received electrical signals into sound, thereby enabling the transmission of broadcast information. The operating status of the loudspeakers directly affects the sound quality and accuracy of information transmission in the broadcast system.

[0003] In public address systems, multiple loudspeakers in the same area are typically connected in parallel, and a fixed voltage is set to drive them to simplify wiring and maintenance. Existing technology primarily determines the operating status of the loudspeakers by detecting changes in the AC and DC impedance of the parallel loudspeaker circuits. However, due to significant differences in the feeder length and path of the loudspeaker circuits, this detection method is often inaccurate and struggles to accurately determine the specific status of each loudspeaker. Furthermore, because the loudspeakers are connected in parallel, existing technology cannot pinpoint the specific condition of an individual loudspeaker, such as short circuit, open circuit, or fault, which complicates troubleshooting and maintenance. Some detection techniques require disconnecting the amplifier and loudspeaker connection during testing, which causes interruptions in sound playback and affects the normal operation of the system. This interruption is unacceptable, especially in high-reliability applications. Summary of the Invention

[0004] The present invention aims to provide an online speaker monitoring system and a public address system to solve the above-mentioned technical problems, realize one-to-one detection of speakers, and improve the detection accuracy of speaker working status.

[0005] To address the aforementioned technical problems, this invention provides an online loudspeaker monitoring system, applicable to public address systems containing multiple loudspeakers, comprising: a host computer, a detection and control device, a power amplifier, and a detection terminal matched to the loudspeakers;

[0006] The first end of the detection and control device is connected to the input end of the power amplifier;

[0007] The second end of the detection control device and the output end of the power amplifier are connected to the input end of each detection terminal; wherein, the output end of the detection terminal is connected to the input end of a speaker;

[0008] The detection and control device is used to mix the received audio signal with a preset ultrasonic signal and send the resulting mixed signal to the power amplifier.

[0009] The power amplifier is used to amplify the received mixed signal and send the resulting amplified mixed signal to each of the detection terminals.

[0010] The detection terminal is used to sample the power amplifier circuit and the speaker circuit to obtain the power amplifier circuit sampling voltage and the speaker circuit sampling current. When the power amplifier circuit sampling voltage and the speaker circuit sampling current include ultrasonic data and the ultrasonic data is within a preset voltage range, it is determined that the power amplifier circuit and the speaker circuit are working normally. Herein, the power amplifier circuit is the circuit between the power amplifier and the detection terminal, and the speaker circuit is the circuit between the detection terminal and the connected speaker.

[0011] The detection control device is also used to collect the detection judgment results of each detection terminal based on the second end, and to feed the detection judgment results back to the host computer.

[0012] In the above scheme, ultrasonic signals are mixed into the power amplifier output signal, enabling real-time monitoring of the speaker circuitry and power amplifier circuitry without disconnecting the speaker from the amplifier. The detection terminal directly collects signals from the connection lines between the power amplifier and the speaker, analyzes the ultrasonic data, and determines the status of the circuitry and the speaker, avoiding playback interruptions. Each speaker is equipped with an independent detection terminal, which collects the sampling current of the speaker circuitry and the sampling voltage of the power amplifier circuitry. By analyzing the amplitude of the ultrasonic signals, the system can accurately determine the specific status of each speaker. By mixing ultrasonic signals into the power amplifier output signal and directly collecting and analyzing signals at the speaker end, the influence of feeder length and path differences is bypassed. The detection terminal collects ultrasonic signals from the power amplifier circuitry and speaker circuitry, rather than using traditional impedance measurements, thus achieving higher detection accuracy and enabling accurate determination of the speaker status.

[0013] In one implementation, the detection and control device is used to mix the received audio signal with an ultrasonic signal of a preset duty cycle, and send the resulting mixed signal to the power amplifier, specifically including:

[0014] The detection and control device includes a first MCU, an RC integrator circuit, and an operational amplifier inverting adder;

[0015] The I / O ports of the first MCU are connected sequentially through the input terminals of the three-stage RC integrator circuit, and the output terminal of the last-stage RC integrator circuit is connected to the inverting input terminal of the operational amplifier inverting adder; wherein, each stage of the RC integrator circuit includes a resistor and a capacitor;

[0016] The first MCU is controlled to output a square wave signal at a preset frequency, and the square wave signal is input to the RC integrator circuit so that the third-order RC integrator circuit converts the square wave signal into an ultrasonic signal.

[0017] The audio signal and the ultrasonic signal are input to the inverting input of the operational amplifier inverting adder, so that the output of the operational amplifier inverting adder outputs the mixing signal; wherein, the mixing signal includes the audio signal and the ultrasonic signal.

[0018] In the above scheme, by mixing an ultrasonic signal into the audio signal, online monitoring is achieved without disconnecting the speaker from the power amplifier, thus avoiding playback interruptions. Using an ultrasonic signal for detection is unaffected by feeder length and path differences, enabling accurate detection of the speaker's status and improving detection precision. A third-order RC integrator circuit effectively filters and smoothly converts the square wave signal into an ultrasonic signal, reducing signal distortion and improving signal quality. The audio and ultrasonic signals are mixed in real-time using an operational amplifier inverting adder; the output mixed signal promptly reflects the speaker's status, improving the system's response speed.

[0019] In one implementation, the detection control device is further configured to collect the detection judgment result of each detection terminal and feed the detection judgment result back to the host computer, specifically including:

[0020] The detection and control device also includes an RS485 communication interface circuit and an Ethernet interface circuit.

[0021] The RS485 communication interface circuit includes a driver chip, a first twisted pair cable, a second twisted pair cable, and...

[0022] The Ethernet interface circuit includes a PHY chip and an isolation transformer; wherein, the Ethernet interface circuit is used to provide physical layer isolation and protection for the first MCU;

[0023] The data transmission pin of the first MCU is connected to the data input pin of the driver chip;

[0024] The data receiving pin of the first MCU is connected to the data receiving output pin of the driver chip;

[0025] The control pin of the first MCU is connected to the enable pin of the driver chip;

[0026] The two ends of the first twisted pair are connected to the first MCU and the driver chip to transmit A and B differential signals;

[0027] The two ends of the second twisted pair are connected to the driver chip and the detection terminal, respectively, for transmitting power signals and grounding signals;

[0028] The first MCU connects to the Ethernet via the PHY chip and the isolation transformer, and feeds back the detection and judgment results to the host computer through the Ethernet interface; wherein, the first MCU and the host computer communicate via Ethernet.

[0029] In the above scheme, the detection and control device can acquire the detection and judgment results of each detection terminal in real time through the RS485 communication interface, ensuring the timeliness and accuracy of the data. The RS485 communication interface uses differential signal transmission (A and B differential signals), which has strong anti-interference capabilities and long-distance transmission performance. Through the driver chip and twisted pair cable, the signal transmission is more stable and reliable, reducing data transmission errors. The PHY chip and isolation transformer in the Ethernet interface circuit realize physical layer isolation and protection for the first MCU, effectively preventing external interference and damage, and improving the reliability of the system. Through the Ethernet interface, the detection and control device can communicate efficiently with the host computer, supporting remote monitoring and management. The Ethernet interface allows the system to be integrated into the existing network infrastructure, facilitating expansion and maintenance.

[0030] In one implementation, the detection control device is further configured to display each detection result on an LCD. Specifically, the detection control device includes a touch LCD display control circuit; wherein the LCD display control circuit is configured to display each detection result; and the LCD display control circuit is further configured to display a warning reminder for detection results that are deemed abnormal.

[0031] In the above solution, the LCD display control circuit can intuitively display the detection results of each detection terminal, allowing users to quickly understand the system status and reduce misjudgments and operational errors. Through the LCD display, the detection control device can show the speaker status in real time, including normal and abnormal, facilitating users' timely understanding of the system's operation. For detection results indicating abnormalities, the LCD display control circuit can provide warnings, helping users quickly locate the fault point and improving troubleshooting efficiency. The touch-screen LCD display control circuit supports touch operation, allowing users to perform menu selection, parameter settings, and other operations via the touchscreen, enhancing user experience and system usability.

[0032] In one implementation, the detection terminal samples the power amplifier circuit and the speaker circuit, specifically:

[0033] The detection terminal includes a second MCU and a sampling circuit, which samples the power amplifier circuit and the speaker circuit based on the sampling circuit.

[0034] The sampling circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first inductor, a second inductor, a bidirectional Zener diode, and a first operational amplifier;

[0035] The positive output terminal of the power amplifier is connected to the first terminal of the speaker and the first terminal of the first resistor;

[0036] The second end of the first resistor is connected to the first end of the second resistor, the first end of the bidirectional Zener diode, and the first end of the first capacitor;

[0037] The second end of the speaker is connected to the first end of the third resistor and the first end of the first inductor;

[0038] The second end of the first inductor is connected to the first end of the second capacitor;

[0039] The second terminal of the second capacitor is connected to the first terminal of the second inductor, the first terminal of the third capacitor, and the first terminal of the fourth capacitor;

[0040] The second terminal of the fourth capacitor is connected to the first terminal of the fourth resistor and the non-inverting input terminal of the first operational amplifier;

[0041] The inverting input terminal of the first operational amplifier is connected to the first terminal of the fifth resistor and the first terminal of the sixth resistor;

[0042] The second end of the fifth resistor is connected to the first end of the fifth capacitor;

[0043] The output terminal of the first operational amplifier is connected to the first terminal of the sixth capacitor and the second terminal of the sixth resistor;

[0044] The second terminal of the first capacitor and the second terminal of the sixth capacitor are connected to the ADC function module of the second MCU;

[0045] The negative output terminal of the power amplifier, the first terminal of the second resistor, the second terminal of the bidirectional Zener diode, the second terminal of the second inductor, the second terminal of the second capacitor, and the second terminal of the fifth capacitor are grounded.

[0046] In the above scheme, the sampling circuit can simultaneously sample the power amplifier circuit and the speaker circuit, comprehensively monitoring the status of both, including the power amplifier output signal, and the resistance, inductance, and capacitance characteristics of the speaker. Through the design of capacitors and filter circuits, noise and interference signals can be effectively suppressed, improving the purity of the sampled signal and enhancing the reliability of the detection. A bidirectional Zener diode is used to protect the sampling circuit from damage by overvoltage or reverse voltage, ensuring the safety and stability of the circuit.

[0047] In one implementation, the second terminal of the first capacitor and the second terminal of the sixth capacitor are connected to the ADC function module of the second MCU, specifically including:

[0048] The detection terminal also includes a filtering circuit;

[0049] The second terminal of the first capacitor is connected to the second ADC module of the second MCU; wherein, the signal transmitted by the first capacitor is the sampling voltage of the power amplifier circuit;

[0050] The second terminal of the sixth capacitor is connected to the first ADC module of the second MCU through the filtering circuit; wherein, the signal transmitted by the sixth capacitor is the sampling current of the speaker circuit, and the filtering circuit is used to perform bandpass filtering on the sampling current of the speaker circuit to attenuate other signals besides the ultrasonic signal.

[0051] In the above scheme, the power amplifier circuit sampling voltage transmitted by the first capacitor is directly connected to the second ADC module of the second MCU, while the speaker circuit sampling current transmitted by the sixth capacitor is connected to the first ADC module after passing through a filter circuit. This achieves separate sampling of the power amplifier circuit and speaker circuit signals, improving detection accuracy. The filter circuit performs bandpass filtering on the speaker circuit sampling current, effectively attenuating interference signals other than ultrasonic signals, ensuring the purity of the sampled signal, and improving detection reliability. By processing the power amplifier circuit sampling voltage and speaker circuit sampling current separately through the two ADC modules of the second MCU, multi-channel parallel detection is achieved, improving the system's detection efficiency.

[0052] In one implementation, the detection terminal further includes a sound pickup circuit, which is used to inspect the sound playback quality of the speaker. Specifically:

[0053] The second ADC module receives the power amplifier line sampling voltage, and the second MCU filters the power amplifier line sampling voltage to identify the audio data and ultrasonic data in the power amplifier line sampling voltage.

[0054] The audio data is used as a reference signal for speaker sound playback detection;

[0055] The sound signal played by the speaker is acquired by the sound pickup circuit and compared with the reference signal. If the deviation rate between the two signals exceeds a preset threshold within a preset time period, the speaker is determined to be playing normally.

[0056] In the above scheme, the actual sound played by the speaker is acquired by the sound pickup circuit and compared with the audio data in the sampling voltage of the power amplifier line, enabling real-time monitoring of the speaker's sound playback quality. Using the audio data in the sampling voltage of the power amplifier line as a reference signal and comparing it with the actual sound played by the speaker can effectively detect whether the speaker is working properly and whether there is any distortion or deviation in the sound. By comparing the deviation rate between the reference signal and the actual sound signal, the speaker's fault condition, such as blockage or damage, can be accurately determined, improving the accuracy of fault diagnosis.

[0057] In one implementation, the step of acquiring the sound signal played by the speaker based on the sound pickup circuit specifically includes:

[0058] The sound pickup circuit includes a microphone, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, and a second operational amplifier;

[0059] The microphone's audio output terminal is connected to the first terminal of the seventh resistor and the first terminal of the seventh capacitor; wherein, the microphone is used to convert the sound signal played by the speaker into an electrical signal;

[0060] The second terminal of the seventh capacitor is connected to the first terminal of the eighth resistor and the non-inverting input terminal of the second operational amplifier;

[0061] The inverting input terminal of the second operational amplifier is connected to the first terminal of the ninth resistor and the first terminal of the tenth resistor;

[0062] The second end of the ninth resistor is connected to the first end of the eighth capacitor;

[0063] The output terminal of the second operational amplifier is connected to the first terminal of the ninth capacitor and the second terminal of the tenth resistor;

[0064] The second terminal of the ninth capacitor is connected to the third ADC function module of the second MCU.

[0065] In the above scheme, the microphone captures the sound played by the speaker and converts it into an electrical signal, exhibiting high sensitivity and fidelity to ensure accurate sound signal acquisition. The second operational amplifier amplifies the acquired sound signal and simultaneously filters it using a combination of resistors and capacitors to remove noise and interference, improving signal quality. Multiple resistors and capacitors are used in the circuit design to adjust the gain and frequency response of the operational amplifier, ensuring the stability and linearity of the sound signal during transmission. This sound pickup circuit is directly connected to the third ADC function module of the second MCU, facilitating digital signal processing and further analysis, and exhibiting good compatibility.

[0066] In one implementation, the detection terminal further includes an ID setting switch; wherein the ID setting switch is used to set the address ID of the detection terminal;

[0067] Each detection terminal is scanned cyclically according to its address ID, so that each detection terminal feeds back the generated detection judgment result to the detection control device based on the received scan signal.

[0068] In the above scheme, each detection terminal can be uniquely identified by setting a unique address ID, facilitating management and control in multi-device systems. The detection control device can automatically detect the status of each terminal through cyclic scanning without manual intervention, improving the system's automation level. Ordered communication via address IDs avoids conflicts caused by multiple detection terminals sending data simultaneously, ensuring efficient and reliable communication.

[0069] Secondly, this application also provides a public address system, including the speaker online monitoring system described above. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of the system framework of an online loudspeaker monitoring system provided in one embodiment of the present invention;

[0071] Figure 2 This is a schematic diagram of a detection and control device provided in one embodiment of the present invention;

[0072] Figure 3 This is a schematic diagram of an ultrasonic signal provided in one embodiment of the present invention;

[0073] Figure 4 This is a schematic diagram of the connection relationship of a sampling circuit provided in one embodiment of the present invention;

[0074] Figure 5 This is a schematic diagram of a detection terminal module provided in one embodiment of the present invention;

[0075] Figure 6 This is a schematic diagram of the connection relationship of a sound pickup circuit provided in one embodiment of the present invention. Detailed Implementation

[0076] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0077] The terms "first" and "second," etc., in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0078] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0079] Example 1

[0080] See Figure 1 , Figure 1 This is a schematic diagram of the system framework of an online loudspeaker monitoring system provided in one embodiment of the present invention. The online loudspeaker monitoring system is suitable for a public address system containing a plurality of loudspeakers, and includes: a host computer, a detection and control device, a power amplifier, and a detection terminal matched to the loudspeakers;

[0081] The first end of the detection and control device is connected to the input end of the power amplifier;

[0082] The second end of the detection control device and the output end of the power amplifier are connected to the input end of each detection terminal; wherein, the output end of the detection terminal is connected to the input end of a speaker;

[0083] The detection and control device is used to mix the received audio signal with a preset ultrasonic signal and send the resulting mixed signal to the power amplifier.

[0084] The power amplifier is used to amplify the received mixed signal and send the resulting amplified mixed signal to each of the detection terminals.

[0085] The detection terminal is used to sample the power amplifier circuit and the speaker circuit to obtain the power amplifier circuit sampling voltage and the speaker circuit sampling current. When the power amplifier circuit sampling voltage and the speaker circuit sampling current include ultrasonic data and the ultrasonic data is within a preset voltage range, it is determined that the power amplifier circuit and the speaker circuit are working normally. Herein, the power amplifier circuit is the circuit between the power amplifier and the detection terminal, and the speaker circuit is the circuit between the detection terminal and the connected speaker.

[0086] The detection control device is also used to collect the detection judgment results of each detection terminal based on the second end, and to feed the detection judgment results back to the host computer.

[0087] In one embodiment, the detection and control device is used to mix the received audio signal with an ultrasonic signal of a preset duty cycle and send the resulting mixed signal to the power amplifier. Specifically, the detection and control device includes a first MCU, an RC integrator circuit, and an operational amplifier inverting adder. The I / O ports of the first MCU are sequentially connected to the input terminals of the third-order RC integrator circuit, and the output terminal of the last-order RC integrator circuit is connected to the inverting input terminal of the operational amplifier inverting adder. Each order of the RC integrator circuit includes a resistor and a capacitor. The first MCU is controlled to output a square wave signal at a preset frequency, and the square wave signal is input to the RC integrator circuit so that the third-order RC integrator circuit converts the square wave signal into an ultrasonic signal. The audio signal and the ultrasonic signal are input to the inverting input terminal of the operational amplifier inverting adder so that the output terminal of the operational amplifier inverting adder outputs the mixed signal.

[0088] See Figure 2 , Figure 2 This is a schematic diagram of a detection control device module provided in one embodiment of the present invention. In this embodiment, the first MCU is an Artery AT32F437, whose core is an ARM-Cortex-M4F, used to realize the overall functional management and control of the detection device system, including setting the detection mode, summarizing the detection data of each detection device terminal, and storing data. See also Figure 3 , Figure 3This is a schematic diagram of an ultrasonic signal provided in one embodiment of the present invention. A 25kHz square wave signal with a 50% duty cycle is output from one I / O port of a first MCU, and is intermittently output at 20Hz with an envelope duty cycle of 20%. This square wave signal is input to a third-order RC integrator circuit, which converts the square wave signal into a near-sine wave 25kHz ultrasonic signal. The output of the third-order RC integrator circuit is connected to the input of an operational amplifier inverting adder, which mixes the audio signal and the ultrasonic signal in opposite phase to generate a mixed signal. For example, the MCU's I / O port is set to output mode to generate a square wave signal at a preset frequency (e.g., 25kHz). The duty cycle of the square wave is controlled by programming and set to 50% to obtain a symmetrical signal. The third-order RC integrator circuit consists of three RC filters connected in series, used to integrate the square wave signal output by the MCU, thereby generating a near-sine wave 25kHz ultrasonic signal. Preferably, the cutoff frequency of each RC circuit is set below the target ultrasonic frequency to ensure effective integration. Then, the audio signal sent by the audio front-end device and the obtained ultrasonic signal are input to the inverting input of the operational amplifier inverting adder. Preferably, the output of the operational amplifier inverting adder is connected to the inverting input through a feedback resistor, forming a negative feedback loop. The output of the operational amplifier inverting adder outputs a mixed signal, which includes the audio signal and the 25kHz ultrasonic signal. The resulting mixed signal is then sent to the power amplifier through the audio output circuit. The audio front-end device captures and outputs the original audio signal, for example, by capturing the sound signal through a microphone. Then, it performs signal preprocessing steps such as amplification, filtering, and analog-to-digital conversion through a preamplifier, filter, and analog-to-digital converter to obtain the audio signal input to the detection and control device. The audio output circuit amplifies the mixed signal output by the operational amplifier inverting adder to a power level sufficient to drive the speaker. This includes filtering and limiting operations to ensure the quality of the output signal. It generally consists of a power amplifier, a filter, and a speaker. Through the above design and connection method, the detection and control device can effectively mix the audio signal and the ultrasonic signal, drive the speaker through the power amplifier, and simultaneously achieve online monitoring of the speaker circuit.

[0089] In one embodiment, the detection control device is further configured to collect the detection judgment results of each detection terminal and feed the detection judgment results back to the host computer. Specifically, the detection control device further includes an RS485 communication interface circuit and an Ethernet interface circuit. The RS485 communication interface circuit includes a driver chip, a first twisted pair, and a second twisted pair. The Ethernet interface circuit includes a PHY chip and an isolation transformer. The Ethernet interface circuit is used for physical layer isolation and protection of the first MCU. The transmit data pin of the first MCU is connected to the data input pin of the driver chip. The receive data pin of the first MCU is connected to the receive output pin of the driver chip. The control pin of the first MCU is connected to the enable pin of the driver chip. The two ends of the first twisted pair are connected to the first MCU and the driver chip for transmitting A and B differential signals. The two ends of the second twisted pair are connected to the driver chip and the detection terminal respectively for transmitting power signals and ground signals. The first MCU connects to the Ethernet via the PHY chip and the isolation transformer, and feeds the detection judgment results back to the host computer through the Ethernet interface. The first MCU communicates with the host computer via Ethernet.

[0090] In this embodiment of the invention, the RS485 communication interface circuit mainly includes a driver chip, a first twisted pair cable, and a second twisted pair cable. The driver chip is a MAX485, used for bidirectional conversion between TTL and RS485 levels. The first twisted pair cable is used to transmit A and B differential signals, and the second twisted pair cable is used to transmit power and ground signals. The transmit data pin of the first MCU is connected to the data input pin of the driver chip. The receive data pin of the first MCU is connected to the receive output pin of the driver chip. The receive enable pin and transmit enable pin of the driver chip are connected to the control pin of the first MCU, controlling the driver chip to operate in receive or transmit mode based on this connection. When the MCU needs to transmit data, it sets the receive enable pin to low and the transmit enable pin to high, causing the MAX485 to enter transmit mode. When the MCU needs to receive data, it sets the receive enable pin to high and the transmit enable pin to low, causing the MAX485 to enter receive mode. In the Ethernet interface circuit, the PHY chip, such as W5500 or LAN8720, is used to handle the Ethernet physical layer functions. An isolation transformer, such as the Pulse H1102, is used for network signal isolation and transmission. The RS485 communication interface circuit enables half-duplex communication between the MCU and the detection terminal, while the Ethernet interface circuit connects the MCU to the Ethernet network for data exchange with a host computer. This design ensures reliable data transmission and system stability.

[0091] In one embodiment, the detection control device is further configured to display each detection result on an LCD. Specifically, the detection control device includes a touch LCD display control circuit; wherein the LCD display control circuit is configured to display each detection result; and the LCD display control circuit is further configured to display a warning reminder for detection results that are deemed abnormal.

[0092] In this embodiment of the invention, the detection control device also integrates an LCD display control circuit, used to display the detection judgment results of each detection terminal, helping operators quickly understand the current detection status; and to provide special displays (such as flashing, color changes, etc.) for detection results judged as abnormal, reminding operators to handle them in a timely manner. Furthermore, users can interact with the LCD display via a touchscreen to view detailed information or make related settings. The first MCU obtains the detection judgment results from the detection terminal. Based on the judgment results, it controls the LCD driver chip to generate corresponding display data. The LCD screen displays the detection results, with the color set to green (normal) or blue (pending confirmation). Users can view detailed information via the touchscreen. When the detection result is abnormal, the first MCU controls the LCD driver chip to generate a special display mode. The LCD screen displays the abnormal result in a flashing red or yellow light. Simultaneously, the interrupt pin of the touch controller is triggered, notifying the first MCU that an abnormal event has occurred. The first MCU can prompt the user to take appropriate measures via the touchscreen. When the user touches the LCD screen, the touch controller detects the touch event and sends the event data to the first MCU via the I2C interface. The first MCU parses the touch event and performs corresponding operations according to the event type (such as click, swipe). For example, when the user clicks the display area of ​​the abnormal result, the system can pop up detailed information or an operation menu. By integrating an LCD display control circuit, the detection control device not only achieves real-time display of detection results but also provides anomaly alerts and interactive functions, significantly improving the system's usability and reliability. This design is suitable for various application scenarios requiring intuitive display and timely feedback.

[0093] In one embodiment, the detection terminal samples the power amplifier circuit and the speaker circuit. Specifically, the detection terminal includes a second MCU and a sampling circuit, which samples the power amplifier circuit and the speaker circuit based on the sampling circuit. The sampling circuit includes a first resistor R5, a second resistor R6, a third resistor R1, a fourth resistor R2, a fifth resistor R4, a sixth resistor R3, a first capacitor C6, a second capacitor C1, a third capacitor C2, a fourth capacitor C3, a fifth capacitor C4, a sixth capacitor C5, a first inductor L1, a second inductor L2, a bidirectional Zener diode D1, and a first operational amplifier IC1. The positive output terminal OUT+ of the power amplifier is connected to the first terminal of the speaker and the first terminal of the first resistor R5. The second terminal of the first resistor R5 is connected to the first terminal of the second resistor R6, the first terminal of the bidirectional Zener diode D1, and the first terminal of the first capacitor C6. The second terminal of the speaker is connected to the first terminal of the third resistor R1 and the first terminal of the first inductor L1. The second terminal of the first inductor L1 is connected to the second inductor C6. The first terminal of capacitor C1 is connected; the second terminal of the second capacitor C1 is connected to the first terminal of the second inductor L2, the first terminal of the third capacitor C2, and the first terminal of the fourth capacitor C3; the second terminal of the fourth capacitor C3 is connected to the first terminal of the fourth resistor R2 and the non-inverting input terminal of the first operational amplifier IC1; the inverting input terminal of the first operational amplifier IC1 is connected to the first terminal of the fifth resistor R4 and the first terminal of the sixth resistor R3; the second terminal of the fifth resistor R4 is connected to the first terminal of the fifth capacitor C4; the output terminal of the first operational amplifier IC1 is connected to the first terminal of the sixth capacitor C5 and the second terminal of the sixth resistor R3; the second terminals of the first capacitor C6 and the sixth capacitor C5 are connected to the ADC function module of the second MCU; the negative output terminal OUT- of the power amplifier, the first terminal of the second resistor R6, the second terminal of the bidirectional Zener diode D1, the second terminal of the second inductor L2, the second terminal of the second capacitor C1, and the second terminal of the fifth capacitor C4 are grounded.

[0094] See Figure 4 , Figure 4This is a schematic diagram of the connection relationship of a sampling circuit provided in one embodiment of the present invention. In this embodiment, the positive output terminal OUT+ of the power amplifier is connected to the first terminal of the speaker and the first terminal of the first resistor R5; the first resistor R5 is used to sample the output voltage of the power amplifier circuit; the second resistor R6 is connected in series with the first resistor R5 to form a voltage divider circuit, which is used to further refine the sampled signal. The bidirectional Zener diode D1 is used to clamp the voltage and protect the circuit from overvoltage impact. The first capacitor C6 is used for filtering and eliminating high-frequency noise. The second terminal of the speaker is connected to the first terminal of the third resistor R1 and the first terminal of the first inductor L1. The third resistor R1 is used to sample the current of the speaker circuit; the first inductor L1 and the second capacitor C1 (C1) form a series resonant frequency selection circuit with a resonant frequency of 25KHz. Under the 25KHz signal, L1 and C1 present a low impedance state, and other frequency signals present a high impedance state. The second capacitor C1 and the first inductor L1 form a series resonant frequency selection circuit; the second inductor L2 and the third capacitor C2 form a parallel resonant circuit with a resonant frequency of 25KHz. At a 25kHz signal, L2 and C2 exhibit high impedance, while signals at other frequencies exhibit low impedance. The third capacitor C2 and the second inductor L2 form a parallel resonant circuit. The fourth capacitor C3 couples the signal, sending the 25kHz signal to the first operational amplifier IC1. The fourth resistor R2, the fifth resistor R4, the sixth resistor R3, the fourth capacitor C3, the fifth capacitor C4, and the first operational amplifier IC1 form a non-inverting operational amplifier circuit. The first operational amplifier IC1 amplifies the 25kHz signal. The fifth resistor R4 is the feedback resistor for the first operational amplifier. The fifth capacitor C4 filters and eliminates high-frequency noise. The sixth resistor R3 sets the gain of the first operational amplifier. The sixth capacitor C5 couples the amplified signal, sending it to the MCU's ADC port. The second terminals of the first capacitor C6 and the sixth capacitor C5 are connected to the MCU's ADC module for AD acquisition.

[0095] The positive output terminal OUT+ of the power amplifier is sampled through a voltage divider circuit formed by the first resistor R5 and the second resistor R6. The second terminal of the speaker samples the current in the speaker circuit through the third resistor R1. A series resonant frequency selection circuit composed of the first inductor L1 and the second capacitor C1 selects the 25kHz signal, attenuating other frequencies. A parallel resonant circuit composed of the second inductor L2 and the third capacitor C2 further selects the 25kHz signal, attenuating other frequencies. The selected 25kHz signal is coupled to the non-inverting input of operational amplifier IC1 through the fourth capacitor C3. Operational amplifier IC1 amplifies the 25kHz signal, and the amplified signal is coupled to the ADC port of the MCU through the sixth capacitor C5 for AD acquisition. A bidirectional Zener diode D1 clamps the voltage to prevent overvoltage damage to the circuit. Capacitors C6 and C4 are used for filtering to eliminate high-frequency noise and ensure signal stability. Through the above sampling circuit, accurate sampling and signal processing of the power amplifier circuit and speaker circuit can be achieved. The resonant frequency selection circuit and amplification circuit ensured the accurate extraction and amplification of the 25KHz signal. Finally, the ADC function module of the MCU was used for AD acquisition, realizing real-time monitoring and protection of the system status.

[0096] In one embodiment, the second terminal of the first capacitor and the second terminal of the sixth capacitor are connected to the ADC function module of the second MCU, specifically including: the detection terminal further includes a filtering circuit; the second terminal of the first capacitor is connected to the second ADC module ADC2 of the second MCU; the second terminal of the sixth capacitor is connected to the first ADC module ADC1 of the second MCU through the filtering circuit; wherein the filtering circuit is used to perform bandpass filtering on the speaker circuit sampling current to attenuate other signals besides the ultrasonic signal.

[0097] See Figure 5 , Figure 5This is a schematic diagram of a detection terminal module provided in one embodiment of the present invention. In this embodiment, the power amplifier circuit is based on the sampling circuit acquiring the output voltage of the power amplifier circuit. The filtering circuit is used to implement bandpass filtering of the 25 kHz ultrasonic signal, thereby significantly attenuating signals outside 25 kHz. An RC-based bandpass filter can be constructed using capacitors and inductors as one implementation of the filtering circuit. The filtering circuit will include capacitors and inductors, and the selection of these components needs to be calculated based on the required cutoff frequency and quality factor. For example, for an RC-based bandpass filter, the values ​​of the capacitors and resistors need to be precisely calculated to achieve a center frequency of 25 kHz. Butterworth filters, Chebyshev filters, or elliptic filters can also be directly used as the filtering circuit. The second terminal of the sixth capacitor is connected to the filtering circuit, which is then connected to the first ADC module of the second MCU. This design ensures that only signals of specific frequencies are transmitted to the ADC module, thereby improving measurement accuracy. It should be noted that the ADC module of the second MCU needs to have sufficient sampling rate and resolution to accurately capture the 25 kHz signal. According to the Nyquist theorem, the sampling frequency should be at least twice the highest frequency of the signal, therefore a sampling rate of at least 50 kHz is required.

[0098] In one embodiment, the detection terminal further includes a sound pickup circuit. Based on the sound pickup circuit, the sound playback quality of the speaker is checked. Specifically: the sampling voltage of the power amplifier line received by the second ADC module is acquired; the sampling voltage of the power amplifier line is filtered based on the second MCU to identify audio data and ultrasonic data in the sampling voltage; the audio data is used as a reference signal for speaker sound playback detection; the sound signal played by the speaker is acquired based on the sound pickup circuit; the sound signal is compared with the reference signal; if the deviation rate between the two signals exceeds a preset threshold within a preset time period, the speaker's playback is determined to be normal.

[0099] In this embodiment of the invention, the sampling voltage of the power amplifier circuit is received by the second ADC module ADC2. This voltage includes an audio signal and a 25kHz ultrasonic signal. Audio signals within the 20Hz to 20kHz frequency band are extracted through software filtering and used as reference data for audio quality comparison. The actual sound signal played by the speaker is acquired by the sound pickup circuit. The actual sound signal is compared with the reference signal within a preset time length, and the deviation rate is calculated. For example, the actual acquired sound signal data is continuously compared with the reference audio data for a preset time period, such as 10 seconds. The deviation rate between the two signals within the preset time length is calculated. The deviation rate may be determined by calculating the mean square error (MSE), peak signal-to-noise ratio (PSNR), or other audio quality metrics. If the deviation rate exceeds a set threshold, the speaker is deemed to be malfunctioning. Based on the magnitude of the deviation rate, the severity of the speaker malfunction can be further determined.

[0100] In one embodiment, the acquisition of the sound signal played by the speaker based on the sound pickup circuit specifically includes: the sound pickup circuit comprising a microphone (MIC), a seventh resistor R01, an eighth resistor R02, a ninth resistor R04, a tenth resistor R03, a seventh capacitor C01, an eighth capacitor C02, a ninth capacitor C03, and a second operational amplifier IC2; the audio output terminal of the microphone (MIC) is connected to the first terminal of the seventh resistor R01 and the first terminal of the seventh capacitor C01; wherein, the microphone is used to convert the sound signal played by the speaker into an electrical signal; the second terminal of the seventh capacitor C01... The output terminal of the second operational amplifier IC2 is connected to the first terminal of the eighth resistor R02 and the non-inverting input terminal of the second operational amplifier IC2; the inverting input terminal of the second operational amplifier IC2 is connected to the first terminal of the ninth resistor R04 and the first terminal of the tenth resistor R03; the second terminal of the ninth resistor R04 is connected to the first terminal of the eighth capacitor C02; the output terminal of the second operational amplifier IC2 is connected to the first terminal of the ninth capacitor C03 and the second terminal of the tenth resistor R03; the second terminal of the ninth capacitor C03 is connected to the third ADC function module ACD3 of the second MCU.

[0101] See Figure 6 , Figure 6This is a schematic diagram of the connection relationship of a sound pickup circuit provided in one embodiment of the present invention. In this embodiment, the microphone (MIC) is a condenser electret microphone used to convert sound into an electrical signal. The seventh resistor R01 provides a bias voltage to the electret microphone, ensuring normal operation. One end is connected to the audio output terminal of the microphone (MIC), and the other end is connected to the power supply terminal Vcc. The seventh capacitor C01 is used for DC blocking, removing the DC component from the microphone output signal and allowing only AC signals (audio signals) to pass through. One end is connected to the audio output terminal of the microphone (MIC), and the other end is connected to the eighth resistor R02 and the non-inverting input terminal of the second operational amplifier IC2. The eighth resistor R02 is connected to the seventh capacitor C01 and the non-inverting input terminal of the second operational amplifier IC2, forming impedance matching at the input terminals. The second operational amplifier IC2 is used to amplify the audio signal output by the microphone. The ninth resistor R04 is connected to the inverting input terminal of the second operational amplifier IC2 and the first end of the eighth capacitor C02 for feedback, stabilizing the amplification factor. Eight capacitors, C02 and C03, are used to couple the feedback signal, remove DC components, and ensure amplifier stability. One end is connected to the second terminal of the ninth resistor R04, and the other end is grounded. The tenth resistor R03 is connected to the inverting input and output of the second operational amplifier IC2, forming a feedback loop to stabilize the amplification factor. One end is connected to the inverting input of the second operational amplifier IC2, and the other end is connected to the output of the second operational amplifier IC2 and the first terminal of the ninth capacitor C03. The ninth capacitor C03 is used to couple the amplified audio signal, remove DC components, and ensure a clean signal. One end is connected to the output of the second operational amplifier IC2, and the other end is connected to the third ADC function module ADC3 of the second MCU.

[0102] The microphone (MIC) converts the sound signal played from the speaker into an electrical signal. A bias voltage is provided to the microphone via resistor R01 (seventh resistor) to ensure its normal operation. Capacitor C01 (seventh capacitor) removes the DC component from the microphone output signal, allowing only the AC signal (audio signal) to pass through. After passing through capacitor C01, the signal is fed to the non-inverting input of the second operational amplifier IC2. The second operational amplifier IC2 amplifies the audio signal. The inverting input forms a feedback loop through resistor R04 (ninth resistor) and capacitor C02 (eighth capacitor) to ensure the stability of the amplification factor. Resistor R03 (tenth resistor) further stabilizes the amplification factor and prevents oscillation. The amplified audio signal is coupled through capacitor C03 (ninth capacitor) to remove the DC component. Finally, the signal is sent to the third ADC module (ADC3) of the second MCU for digital acquisition.

[0103] In one embodiment, the detection terminal further includes an ID setting switch; wherein the ID setting switch is used to set the address ID of the detection terminal, and to cyclically scan each detection terminal according to the address ID of each detection terminal, so that each detection terminal feeds back the generated detection judgment result to the detection control device based on the received scan signal.

[0104] In this embodiment of the invention, the ID setting switch allows users or production personnel to set a unique address ID for each testing terminal. This ID is the identifier of the testing terminal, used to distinguish different devices in the system. Through the ID setting switch, the address ID of the testing terminal can be flexibly set or modified to adapt to different testing environments and requirements. The first MCU in the testing control device periodically sends a scan signal, cyclically scanning the address ID of each testing terminal. This process ensures that the system can communicate with all connected testing terminals. When a testing terminal receives a scan signal, it checks whether the signal matches its own address ID. If they match, the testing terminal feeds back the generated testing judgment result to the testing control device. The testing control device collects the feedback data from each testing terminal and performs further processing and analysis to evaluate the overall testing results.

[0105] This invention provides an online speaker monitoring system. During operation, the detection terminal and the speaker are positioned as close as possible to ensure the speaker's input signal comes from the power amplifier, and the power amplifier's input signal comes from the detection control device. For example, the power amplifier volume is adjusted to above 70% to ensure the power amplifier and speaker operate in a high-sensitivity state. The connection between the power amplifier and speaker is confirmed to be normal, avoiding short circuits or poor contact. An initialization setting is required when the system is used for the first time or when the number of speakers and detection terminals changes. This is achieved by operating the detection control device to enter the initialization mode. The detection control device sends a test signal (such as a 25kHz ultrasonic signal) to the power amplifier and speaker, and collects reference data on the power amplifier circuitry, speaker circuitry, and sound quality through the detection terminal. The reference data includes: the amplitude of the 25kHz ultrasonic signal in the power amplifier circuitry; the amplitude of the 25kHz ultrasonic signal in the speaker circuitry; and the audio signal played by the speaker (20-20kHz frequency band). After initialization, the system saves the collected reference data in the detection control device as a comparison standard for subsequent tests.

[0106] The accuracy of the reference data is crucial to ensure the proper functioning of all devices during system initialization. The first MCU of the detection and control device continuously outputs a square wave signal, which is shaped into a quasi-sine wave signal by an RC integrator circuit. This signal is then mixed with the audio signal by a mixing circuit and sent to the power amplifier for amplification. Approximately 5V of 25kHz ultrasonic signal is generated at the power amplifier output terminals OUT+ and OUT-. The detection terminal receives this signal through the OUT+ and OUT- input interfaces. The audio and 25kHz ultrasonic signals acquired by the power amplifier line voltage sampling circuit are digitally acquired by the second MCU's second ADC function module ADC2. The MCU uses software filtering to separate the audio signal data and the 25kHz ultrasonic signal data. The audio signal data serves as the reference for speaker sound detection. The 25kHz ultrasonic signal data is used to determine the state of the power amplifier circuit. If the MCU detects that the amplitude of the 25kHz ultrasonic signal is within a predetermined range, the power amplifier circuit is considered normal; otherwise, it is considered abnormal. The speaker loop current sampling circuit and the 25kHz filtering circuit extract the 25kHz signal, which is digitally acquired by the second MCU's first ADC function module ADC1. If the amplitude of the 25kHz ultrasonic signal is detected within a predetermined range, the speaker circuit is considered normal; otherwise, it is considered abnormal. The detection is performed continuously in real time, and the results are compared with baseline data. If, for more than 5 seconds, the data from the second ADC module ADC2 (power amplifier circuit) or the data from the first ADC module ADC1 (speaker circuit) exceeds the set tolerance range, it is considered abnormal. Abnormal situations include: power amplifier circuit abnormalities (such as low signal amplitude or no signal); speaker circuit abnormalities (such as speaker open circuit or signal attenuation). The signal acquired by the second ADC function ADC2 of the second MCU in the detection terminal includes both audio and 25kHz ultrasonic signals. Audio signal data within the 20-20kHz frequency band is extracted through software filtering and used as baseline data for audio quality comparison. The sound signal played by the speaker is acquired through the sound pickup circuit and compared with the baseline data for audio quality comparison. If the deviation rate between the two sets of data (baseline data and acquired data) exceeds the set tolerance range for more than 10 consecutive seconds, the speaker sound quality is considered abnormal. Based on the deviation rate of the data, the severity of the abnormality can be further determined. Slight deviation: The speaker may have slight distortion. Severe deviation: The speaker may have a major malfunction (such as a damaged voice coil or abnormal vibration system).

[0107] Furthermore, each testing terminal independently completes its own testing tasks, including power amplifier circuit testing, speaker circuit testing, and sound quality testing. The testing control device communicates with each testing terminal in a round-robin fashion via an RS485 bus. It acquires the testing data from each terminal one by one and displays the data status on the LCD. If any abnormality is found (such as a power amplifier circuit malfunction, speaker circuit malfunction, or sound quality malfunction), the testing control device will display an alarm on the LCD screen. If the system is connected to a host computer or PC, the testing control device will upload the testing data to the corresponding host computer or PC for further analysis and recording.

[0108] As an optimized embodiment of the present invention, a public address system is also provided, including the online speaker monitoring system described above.

[0109] This invention provides an online loudspeaker monitoring system. By mixing ultrasonic signals into the power amplifier output signal, real-time monitoring of the loudspeaker circuitry and power amplifier circuitry can be achieved without disconnecting the loudspeaker from the amplifier. The detection terminal directly collects signals from the connection lines between the amplifier and the loudspeaker, analyzes the ultrasonic data, and determines the status of the circuitry and the loudspeaker, avoiding playback interruptions. Each loudspeaker is equipped with an independent detection terminal, which collects the sampling current of the loudspeaker circuitry and the sampling voltage of the power amplifier circuitry. By analyzing the amplitude of the ultrasonic signals, the system can accurately determine the specific status of each loudspeaker. Mixing ultrasonic signals into the power amplifier output signal and directly collecting and analyzing signals at the loudspeaker end bypasses the influence of feeder length and path differences. The detection terminal collects ultrasonic signals from the power amplifier circuitry and the loudspeaker circuitry, rather than using traditional impedance measurements, thus achieving higher detection accuracy and enabling accurate determination of the loudspeaker status.

[0110] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and substitutions without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A loudspeaker online monitoring system, suitable for use in a public address system comprising a number of loudspeakers, characterized in that, The system comprises: a host computer, a detection control device, a power amplifier, and detection terminals matched with the loudspeakers; a first end of the detection control device is connected with an input end of the power amplifier; a second end of the detection control device and an output end of the power amplifier are connected with an input end of each detection terminal; and an output end of the detection terminal is connected with an input end of a loudspeaker. The detection control device is configured to mix a received audio signal with a preset ultrasonic signal, and send a mixed signal obtained to the power amplifier. The power amplifier is configured to amplify the mixed signal received, and send a mixed amplified signal obtained to each detection terminal. The detection terminal is configured to sample a power amplifier circuit and a loudspeaker loop to obtain a power amplifier circuit sampling voltage and a loudspeaker loop sampling current, and determine that the power amplifier circuit and the loudspeaker loop are working normally when the power amplifier circuit sampling voltage and the loudspeaker loop sampling current contain ultrasonic data and the ultrasonic data is within a preset voltage range. The detection control device is further configured to collect detection determination results of each detection terminal based on the second end, and feed back the detection determination results to the host computer. When the system is used for the first time or the number of loudspeakers and detection terminals changes, an initialization setting is performed; the detection control device is operated to enter an initialization mode; the detection control device sends a test signal to the power amplifier and the loudspeaker, and collects baseline data of the power amplifier circuit, the loudspeaker loop, and sound quality through the detection terminal; the baseline data includes: an ultrasonic signal amplitude of the power amplifier circuit; an ultrasonic signal amplitude of the loudspeaker loop; an audio signal played by the loudspeaker; after the initialization is completed, the system saves the collected baseline data in the detection control device as a comparison standard for subsequent detection. The detection terminal samples the power amplifier circuit and the loudspeaker loop, specifically: The detection terminal comprises a second MCU and a sampling circuit, and samples the power amplifier circuit and the loudspeaker loop based on the sampling circuit. The sampling circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first inductor, a second inductor, a bidirectional voltage stabilizing diode, and a first operational amplifier. A positive output end of the power amplifier is connected with a first end of the loudspeaker and a first end of the first resistor. A second end of the first resistor is connected with a first end of the second resistor, a first end of the bidirectional voltage stabilizing diode, and a first end of the first capacitor. A second end of the second capacitor is connected with a first end of the second inductor, a first end of the third capacitor, and a first end of the fourth capacitor. ​ The second end of the fourth capacitor is connected with the first end of the fourth resistor and the non-inverting input end of the first operational amplifier; The inverting input end of the first operational amplifier is connected with the first end of the fifth resistor and the first end of the sixth resistor; The second end of the fifth resistor is connected with the first end of the fifth capacitor; The output end of the first operational amplifier is connected with the first end of the sixth capacitor and the second end of the sixth resistor; The second end of the first capacitor and the second end of the sixth capacitor are connected with the ADC function module of the second MCU; The negative output end of the power amplifier, the first end of the second resistor, the second end of the second inductor, the second end of the second capacitor and the second end of the fifth capacitor are grounded.

2. A loudspeaker online monitoring system as claimed in claim 1, characterized in that The detection control device is used for mixing the received audio signal with the preset duty ratio ultrasonic signal, and sending the obtained mixed signal to the power amplifier, and specifically comprises: The detection control device comprises a first MCU, an RC integration circuit and an operational amplifier reverse adder; The IO port of the first MCU is connected with the input end of the third-order RC integration circuit in sequence, and the output end of the last-order RC integration circuit is connected with the inverting input end of the operational amplifier reverse adder; wherein each-order RC integration circuit comprises a resistor and a capacitor; The first MCU is controlled to output a square wave signal at a preset frequency, and the square wave signal is input to the RC integration circuit, so that the third-order RC integration circuit converts the square wave signal into an ultrasonic signal; The audio signal and the ultrasonic signal are input to the inverting input end of the operational amplifier reverse adder, so that the output end of the operational amplifier reverse adder outputs the mixed signal; wherein the mixed signal comprises the audio signal and the ultrasonic signal.

3. A loudspeaker online monitoring system as claimed in claim 2, wherein, The detection control device is also used for collecting the detection judgment result of each detection terminal and feeding back the detection judgment result to the upper computer, and specifically comprises: The detection control device further comprises an RS485 communication interface circuit and an Ethernet interface circuit; The RS485 communication interface circuit comprises a driving chip, a first twisted pair line, a second twisted pair line, The Ethernet interface circuit comprises a PHY chip and an isolation transformer; wherein the Ethernet interface circuit is used for isolating and protecting the physical layer of the first MCU; The data transmission pin of the first MCU is connected with the data input pin of the driving chip; The data receiving pin of the first MCU is connected with the receiving output pin of the driving chip; The control pin of the first MCU is connected with the enable pin of the driving chip; The two ends of the first twisted pair line are connected with the first MCU and the driving chip, and are used for transmitting A and B differential signals; The two ends of the second twisted pair line are respectively connected with the driving chip and the detection terminal, and are used for transmitting power supply signals and ground signals; The first MCU realizes connection with Ethernet through the PHY chip and the isolation transformer, and feeds back the detection determination result to the upper computer through an Ethernet interface; wherein the first MCU communicates with the upper computer through Ethernet.

4. A loudspeaker online monitoring system as claimed in claim 1, wherein, The detection control device is also used for LCD display of each detection determination result, in particular: The detection control device comprises a touch LCD display control circuit; wherein the LCD display control circuit is used for displaying each detection determination result; The LCD display control circuit is also used for warning display and reminding of the detection determination result of abnormal determination.

5. A loudspeaker online monitoring system as claimed in claim 1, wherein, The second end of the first capacitor and the second end of the sixth capacitor are connected with an ADC function module of the second MCU, in particular comprising: The detection terminal further comprises a filter circuit; The second end of the first capacitor is connected with a second ADC module of the second MCU; wherein the signal transmitted by the first capacitor is a power amplifier circuit sampling voltage; The second end of the sixth capacitor is connected with a first ADC module of the second MCU through the filter circuit; wherein the signal transmitted by the sixth capacitor is a loudspeaker loop sampling current, and the filter circuit is used for band-pass filtering of the loudspeaker loop sampling current to attenuate other signals except the ultrasonic signal.

6. A loudspeaker online monitoring system as claimed in claim 5, wherein, The detection terminal further comprises a sound pickup circuit, and the sound playback quality of the loudspeaker is tested based on the sound pickup circuit, in particular: The power amplifier circuit sampling voltage received by the second ADC module is acquired, and the audio data and ultrasonic data in the power amplifier circuit sampling voltage are identified based on the second MCU; The audio data is used as a reference signal for loudspeaker sound playback detection; Based on the sound signal collected by the sound pickup circuit, the sound signal is compared with the reference signal, and if the deviation rate of the two signals within a preset time length exceeds a preset threshold, it is determined that the loudspeaker plays normally.

7. A loudspeaker online monitoring system as claimed in claim 6, wherein, The sound signal collected by the sound pickup circuit is based on: The sound pickup circuit comprises a microphone, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, and a second operational amplifier; An audio output end of the microphone is connected with a first end of the seventh resistor and a first end of the seventh capacitor; wherein the microphone is used for converting the sound signal played by the loudspeaker into an electric signal; A second end of the seventh capacitor is connected with a first end of the eighth resistor and a non-inverting input end of the second operational amplifier; An inverting input end of the second operational amplifier is connected with a first end of the ninth resistor and a first end of the tenth resistor; A second end of the ninth resistor is connected with a first end of the eighth capacitor; An output end of the second operational amplifier is connected with a first end of the ninth capacitor and a second end of the tenth resistor; A second end of the ninth capacitor is connected with a third ADC function module of the second MCU.

8. A loudspeaker online monitoring system as claimed in claim 1, wherein, The detection terminal further comprises an ID setting switch; wherein the ID setting switch is used to set the address ID of the detection terminal; Each of the detection terminals is cyclically scanned according to the address ID of each of the detection terminals, so that each of the detection terminals feeds back the generated detection determination result to the detection control device based on the received scanning signal.

9. A public address system characterized by, A loudspeaker online monitoring system comprising the detection terminal according to any one of claims 1 to 8.

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