The public address system is currently a system demanded by all walks of life, and it is used in hotels, shopping malls, parks, scenic spots and other places. In actual use, we will find that some broadcasting systems are electro-acoustic, natural and smooth, but some have some noise and whistling. Faced with this situation, how should we deal with it?
1. Purchase high-quality broadcasting equipment
The system broadcasting equipment selects products with good performance indicators and strong anti-interference ability. The anti-interference ability of broadcasting equipment depends on the noise suppression ability, and is restricted by the circuit, manufacturing process and materials of broadcasting equipment. Therefore, if the budget permits and you want better results, it is recommended to buy higher-end broadcasting equipment, and you will get what you pay for, which is the same forever.
2. Correctly connect the signal lines between the devices
The quality of the equipment is good, and attention should be paid to the connection between the equipment signal lines. If the connection is incorrect or improper, even a device with good performance will not be able to exert its excellent quality. Grounding is an important technical measure to suppress noise, prevent interference, and improve reliability. Correct grounding can suppress the influence of interference on the system, and it can also inhibit the external radiation interference of broadcasting equipment; on the contrary, wrong grounding will introduce serious interference, and even make broadcasting equipment unable to work normally. All power cables and signal cables are protected by metal pipes, which can provide a certain shielding effect.
3. Do not weld shielded wires at will
In the process of equipment installation in the equipment room, do not weld shielded wires at will for convenience, otherwise it is easy to form a closed loop and cause system noise problems. Effective methods to prevent the formation of a closed loop: (1) One end of the shielding layer is grounded (usually at the signal input end), and the other end is open; (2) The grounding point of the chassis and the signal grounding point are distinguished.
4. Purifying power
When designing the power supply, a separate power transformer should be designed; if unconditional, a separate power supply can be used, separate from the air conditioner, lighting and other equipment, or use an isolation power transformer, or install a filter on the power input of the broadcasting equipment to reduce noise Filter out.
5. System isolation
Radio stations often use telephone lines to transmit audio broadcast live signals. Since different subsystems have their own independent grounding systems, once the two systems are grounded, ground noise will inevitably form. On the other hand, after the two subsystems in the flat are interconnected, even if single-ended shielded grounding and long-line segmented grounding are used, there is no way to solve the radiated interference noise caused by long-distance transmission, especially when the huge telephone network is used for transmission. A good measure at this time is to adopt an isolation method and install an audio isolation transformer between the two systems to isolate them from each other.
6. Daily maintenance
Regularly check and test the background music function to ensure that the system functions can be used normally; regularly test the speaker loop to ensure that the speaker loop is in a normal state, effectively avoiding normal use in emergencies; taking into account that electronic equipment is susceptible to dust, etc. If the equipment is affected and malfunctions, it needs to be cleaned regularly during the use of the equipment. When cleaning the dust, you need to use special tools, and be careful not to transfer dust into the equipment.
The final effect of the public address system is related to the quality of the equipment, installation and debugging, and subsequent maintenance. In order to prevent noise and whistling, the above 6 points must be paid attention to.
Attachment: Methods to solve the problems of noise and howling during the debugging of public broadcasting projects
1. First exclude external factors:
There are only three external causes that cause current sound or noise problems: external sound source equipment, excessive noise on site, and system power supply problems. Let's eliminate them one by one, first remove the external audio source, and then turn off all the microphones that are turned on at the scene to cut off the noise pickup of the scene, and then confirm whether this power supply shares the same power supply with other large-scale power systems. Because if it shares a power supply with other large-scale electrical systems, its use will greatly affect the change of current, thus generating current sound.
2. Gradually eliminate various problems in the internal system:
(1) Minimum system method
In our system, it is usually composed of front-end equipment, peripheral equipment, and back-end equipment. Let's remove all the peripheral equipment first. For example: connect the mixer to the power amplifier and the power amplifier to the speakers to see if there is any noise. If there is still, we will discard the mixer. If there is, it is the background noise of the power amplifier, which is a quality problem and can only be replaced. Up. If not, it means that the setting of the mixer is incorrect or the quality is wrong, depending on whether the gain is adjusted too large. If there is no problem with the minimum system, it must be the discarded pile of peripherals. At this time, we have to add the peripheral equipment one by one, and then check in detail whether it is a device setting problem or a quality problem. For example, has the noise reducer been adjusted well, has the equalizer gain been too large, and so on.
(2) Replacement method
In many projects, there may be more than one system, and there may be two or more of the same equipment. We change the equipment that is found to be defective and replace it with another equipment in the conference room that has no problem. If the problem is solved, the same settings Now, that is the problem of the equipment. If the problem still exists, then there are other problems in the system that you haven't found yet, and we need to check again carefully.
(3) Instrument measurement method
Use multimeters, level meters and other measuring instruments to measure the impedance of the speakers and whether the output level of the equipment is normal. Through the above steps and methods, I believe that the noise problem in the system will be solved soon.
Solve the howling problem:
This problem occurs because the sound from the speaker is transmitted to the microphone to form a loop, and howling appears after multiple amplifications. The best way is to physically separate the path between the two. For example, when we choose a microphone, try to use directional instead of non-directional (omnidirectional mice). During use, try not to use the microphone. Directly facing the speaker. However, because there are multiple microphones, the placement of the speakers is fixed and cannot be changed. Then we can only use peripheral equipment to complete this function, such as feedback suppressor, use smartlive to find the howling point, and put it on the equalizer. The corresponding frequency point is attenuated.
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