The sound reinforcement project is a method for processing the original sound by means of building acoustics and electroacoustics, so as to achieve the desired effect of the listening effect. The sound reinforcement system is divided into an indoor sound reinforcement system and an outdoor sound reinforcement system. The two differ greatly during operation. The indoor sound reinforcement is greatly affected by the room acoustic conditions, and the outdoor sound reinforcement is more affected by the natural environment. The design of sound reinforcement system is very targeted. Due to different applications, the selection and use of equipment are also different. According to the purpose, the sound reinforcement system can be divided into: language sound reinforcement system, music sound reinforcement system, stage sound reinforcement system, etc. Although the equipment and peripheral equipment selected by the sound reinforcement system are different according to their needs, their brand, function and quality will also be different, but the core is the same, that is, on the premise of achieving the purpose of sound reinforcement, the quality of the sound return is guaranteed. Figure 1 shows a relatively complete sound reinforcement system. Figure 1 General sound reinforcement system connection diagram. 1 Microphones are prone to problems in sound reinforcement work The microphone is the first link of the sound reinforcement system, and its quality and performance are critical to the sound reinforcement system. According to the requirements of use, you can choose wired microphone or wireless microphone. Wired microphones have a wide frequency response range, high sensitivity, low distortion, good transient effects, but poor mobility. Therefore, they are mostly used in fixed locations; wireless microphones are more and more widely used due to their beautiful appearance and flexible use, but they need Avoid problems such as blind spots. Pay attention to the following issues when using the microphone. 1.1 Wired microphone 1) impedance matching The premise of converting sound signals into electrical signals is to ensure high fidelity of audio signals. In order to achieve this, the load of the microphone must be greater than 5 times its internal resistance (microphone output impedance 5Zout = mixer input impedance Zin). The connection between the input impedance of the sound console and the microphone can not affect the normal operation of the equipment. Although the output impedance of the microphone and the input circuit of the mixer will have some energy loss in use, it can be compensated by the amplifier circuit of the mixer, otherwise it will not only affect the output level of the microphone, but even cause signal distortion. The transmission power is maximum when the impedance is matched. 2) Phase problem If multiple microphones are connected to the mixer, the phase problem must be considered. When the phases of the two microphones are opposite, the signals will cancel each other after being sent to the mixer, and the phenomenon is that the sound becomes significantly smaller. The solution is to reverse the welding of one of the microphones and re-weld. The socket of each microphone can only be connected to one microphone. Do not try to use it in parallel because it will change the state of the microphone load, which will cause many unexpected troubles. When working with more than two microphones, since the signal strength of each sound source directly reaching the microphone closest to it is almost equal to the signal strength of its reaching the adjacent microphone, the distance between the two microphones should reach 3 More than times, making the interference phenomenon relatively weak, the industry calls it the "Trinity Principle." Figure 2 Schematic diagram of the Trinity principle 1.2 Wireless microphone The wireless microphone can convert the picked-up audio signal into electromagnetic wave and emit it to be received by the receiver and then restore it to audio signal. It is convenient to use without the restriction of microphone line. This microphone is suitable for working in close range. Sometimes the signal will be lost, that is, the "dead spot". The phenomenon is that the sound pickup signal is very weak or even disappears, which will seriously affect the work. 1) The wireless microphone system is composed of a microphone head, a transmitter and a receiver. There must be no object between the transmitter and the receiver to prevent the receiver from receiving signals. 2) If there is a camera service on site, the setting of the antenna is higher than the camera and lower than the light stand, because they will interfere with the working frequency of the wireless microphone, causing a radio wave blind zone or disturbing the radio wave propagation path. 3) The RF signal indicator on the receiver is the most intuitive display of the reception status of the signal, so it must be placed within the observation range of the sound engineer to take timely measures according to the display status. 4) The frequency of the wireless microphone is selected by the knob. After the selection, the knob should be fixed to prevent misoperation. 2 Methods for eliminating noise and feedback phenomena 2.1 Noise phenomenon and elimination method There are many reasons for the noise generated by the sound reinforcement system. To sum up, it can be determined in three aspects: the noise generated by the power supply equipment, the noise generated by the external electrical equipment, and the inherent noise of the system itself. 1) Noise generated by power supply equipment This phenomenon rarely occurs in high-standard sound reinforcement sites, because these places consider the problem of power supply noise before construction and solve it in engineering design. This phenomenon mostly occurs in places where the sound reinforcement conditions are not very good. For example, some places do not change the stage lighting by changing the voltage, but use the electronic circuit to control the conductivity of the thyristor and the method of controlling the AC waveform area. Control the output power, thereby changing the brightness of the light. This method causes noise in sound reinforcement. For this phenomenon, two of the three-phase electricity can be used for lighting, and the remaining one can be used for the sound reinforcement system. There is another possibility for the appearance of power equipment noise, that is, the interference of power grid clutter. The State Grid is public. Household power and factory equipment are connected in parallel to the power grid. These equipment will bring various voltage sources and unpredictable noise sources due to excessive power consumption. For these noise sources, you can take measures to eliminate the noise phenomenon in your own work. If you can use a voltage regulator to increase the low voltage and adjust it to about 220 V, the electromagnetic circuit in the voltage regulator can also eliminate some noise waves in the power supply. After the voltage is adjusted, the regulated power supply can be used to make the adjusted voltage relatively stable. The voltage regulator can recognize the voltage value higher or lower than 220 V, and correct it to the normal range through the servo circuit. 2) Noise generated by external radio waves This kind of interference is mainly directed to wireless microphones. There are many wireless communication devices now, and even taxi dispatch has a wireless calling system, so it is best to check whether the transmission and reception frequencies of the microphone can be adjusted before using the wireless microphone to avoid those If you don't want to meet the frequency, choose a wireless microphone that can work in the UHF (Ultra High Frequency) band. The chance of problems will be smaller. The grounding point of the audio system must be independent (do not share with the power supply). If the system input terminal is grounded, the output terminal is also grounded. The noise signal has been amplified and is not easy to eliminate, and because the input and output terminals are equipotential, it is easy to generate feedback. 3) The inherent noise of the system You can see various audio processing peripheral devices in Figure 1, but these devices are double-edged swords: on the one hand, they help the sound engineer to complete the sound reinforcement task, on the one hand, due to the connection of multi-level equipment, the electrical noise generated Affect the quality of sound reinforcement work. If such problems occur in the work, the sound engineer must determine the level of system noise and try to solve them. After starting up, if there is noise, first cut off the power of the wireless microphone receiver. If there is still noise, it means that the crux is not at this level; you can turn off the GAIN knob in turn on each channel on the mixer. No, it means that the problem is here. If all input channels are turned off and there is noise, go to the next step; turn off the mixer power, so that the entire mixer includes bus, group, return, auxiliary, master control , Intercom and oscillation systems were investigated; if there is still noise, then check the peripheral equipment, namely the exciter, compressor, feedback suppressor, equalizer, frequency divider, effect device and power amplifier. This work is very tedious, and it is necessary to judge one by one, and then determine which equipment the noise is from before processing. When performing electronic musical instruments such as rock music, the electronic musical instruments and electro-acoustic equipments that the actors carry have been used many times, and some connectors have been loosened, which can cause noise due to poor contact. This kind of noise is sometimes absent, the volume is very loud during the performance, the noise is covered, and the noise will be very prominent when the performance stops, the experienced musicians will immediately turn off the power of their instruments after the performance stops (the output power Level off), so that the noise of your own instrument cannot enter the sound reinforcement system, but inexperienced players do not have this good habit, which requires the sound engineer to immediately put the corresponding fader at the end of the electronic instrument Pull down to cut off the noise to prevent noise problems. 2.2 Feedback phenomenon and elimination method Howling sounds in sound reinforcement systems are very unpleasant, and this is acoustic feedback. Acoustic feedback is the positive feedback generated after the signal is superimposed and amplified many times. This phenomenon will affect the normal work of sound reinforcement and burn the equipment. Therefore, the elimination of the feedback phenomenon is an indispensable skill of the sound engineer. According to the author's experience, there are at least three reasons for the feedback phenomenon: the first is that the gain is too large, the second is that the microphone is in the sound area of ​​the speaker and is relatively close to the speaker, and the third is the improper use of the device. Some sound engineers open the opening on the input channel of the mixer very much, and the fader only pushes up a bit. This is wrong, because in the actual work, once there is a climax on the scene and the volume is too large, the sound engineer will definitely Pull the fader instinctively, and there is not much margin for the fader down, which will make the work very passive, and it cannot be ruled out that after the mixer has been working for a long time, the lower part of the fader must be more worn than the upper part. There may be noise. The correct method is: first turn off the gain, push the fader to 4/5 of the full stroke, and then turn the gain knob to the appropriate position. At the sound reinforcement site of the radio station, I often see that several or even dozen faders are basically on the same straight line, and the mouths are different. Some sound engineers also use white tape to stick the edge of the fader. A straight line is used as a mark, and the "howling" point is near the white line. These are all tested in preparation and are very practical. The working environment cannot be changed greatly because of the need for sound reinforcement, so the sound engineer must learn to avoid problems as far as possible when conditions permit. For example, the distance and angle between the microphone and the speaker are often overlooked. If the sound enters the microphone, it will generate feedback. If the microphone is too close to the speaker, and the speaker is facing the microphone, it will bury hidden dangers. Therefore, be sure to pay attention to the distance and angle to the speaker when placing the microphone. You can also use the device to eliminate feedback. Acoustic feedback suppressors, frequency converters, and equalizers all have the effect of eliminating feedback. Any problem may occur in the sound reinforcement work, so make preparations in advance, select equipment according to the specific working conditions, and carefully check the equipment after selecting the equipment. The position of the knob and buttons of the equipment must be correct. Using a wireless microphone, be sure to remind him not to perform near the speaker to avoid feedback. 3 Preparations for different sound reinforcement tasks To do sound reinforcement work, business ability and sense of responsibility are indispensable. The sound reinforcement tasks of radio stations are different in nature, and there are many types of political meetings and public welfare performances. Therefore, the sound engineer must carefully prepare all aspects of the sound reinforcement according to the different tasks, and strive to complete the task successfully. 3.1 Political sound reinforcement work The sound conditions of this kind of sound reinforcement work place are generally better, so the technical work is relatively less, mainly due to the psychological pressure of the sound engineer, and making perfect preparations is the best decompression measure. The author's experience is to fully understand the situation on the job site under the conditions under his control. The equipment must be reliable. It is best to use the equipment that you are familiar with. After the installation and commissioning, record some useful data in the book; Make sure that the connection and the bolt board are in good contact. After the equipment is adjusted, it is best not to stay away from the scene. Keep in touch with the guards to ensure that unrelated personnel do not approach the sound reinforcement equipment. Feedback whistle must not appear during the conference or performance. The sound engineer should find the whistle point during the joint tuning (intuitively reflected to the position of the fader). It is best to mark this point on the mixer. And keep a safe distance from it at work. The best sound reinforcement effect area should be based on the position of the chief. The listening effect here should be the most ideal. The sound engineer should try to listen to these seats before the performance. If possible, it is best to ask the industry personnel (such as the director) to jointly consult . If it is a performance of higher specifications, the scene will be very large, and there are many microphones used, but you must not keep all microphones on for a long time because of fear of missing signals. This will not only cause excessive noise, but may also cause Feedback. This requires the sound engineer to be highly concentrated during the tuning process, and there must be no accident of microphone mute (forgetting to push a certain fader), so it is best to carefully understand the performance type of each program and list it in the program list. The detailed operating procedures for each program are marked on the top to avoid operational errors. 3.2 Public welfare performance sound reinforcement work Most of these activities are held in the open air. Although there is no indoor acoustic problem, the loss of sound energy is very large. Therefore, the sound equipment for outdoor sound reinforcement must have a sufficiently powerful rated power. Have enough penetration, otherwise there will be problems with listening to seats farther away. The sound engineer should make a plan for the equipment configuration in advance, and negotiate with the relevant departments in advance about installation and commissioning and some special requirements. The field of outdoor sound reinforcement work is generally very chaotic. The sound system circuit protection measures must be taken. The cover can be used to cover the circuit according to the actual situation. Understand how emergency power supply will be provided in an emergency, and make sure to contact the person in charge of on-site power supply. In the event of a power outage, the correct handling method should be adopted immediately to minimize losses. There are many unpredictable situations hidden in outdoor sound reinforcement work. If there is a problem, it is necessary to calm down. Fiber Patch Panel is to fix and manage fiber optic cables inside the box as well as provide protection,which can be loaded with different adapters interface,related fiber accessories and fiber pigtails. It`s 19 inch,made of 1.0mm cold-rolling steel.The main types of fiber optic patch panel are including 4 Port Fiber Patch Panel, 8 Port Fiber Patch Panel , 12 port fiber patch panel ,24 port fiber patch panel ,48 port fiber patch panel, 96 port fiber patch panel ,144 port fiber patch panel .They are widely used in local area network ,CATV network ,FTTX system ,wide area network ,test instruments.Foclink,a reliable supplier of fiber patch panel,is always beside u 7*24. Fiber Patch Panel 4 Port Fiber Patch Panel,8 Port Fiber Patch Panel,12 Port Fiber Patch Panel,24 Port Fiber Patch Panel Foclink Co., Ltd , https://www.scfiberpigtail.com
