1. The inherent noise of the system equipment itself
At present, the single-machine technical indicators of broadcast control equipment are very high, and there are very low local noise indicators. But when multiple devices are cascaded, the noise builds up. In practical applications, some low-end audio equipment will have poor communication noise due to poor internal power supply filtering, and sometimes severe noise will be formed in the audio system.
2. Noise caused by external electromagnetic radiation interference
Such as mobile phones, walkie-talkies and other communication equipment, high-frequency electromagnetic radiation interference, ambient air conditioning, car ignition, electric welding and other electrical pulse radiation, studio lighting control using thyristor rectifier equipment generated by the radiation, will be directly mixed through the audio transmission line transmission Noise generated in the signal, or through the casing of the poorly shielded machine, interferes with the internal circuitry of the machine to generate interference noise.
3. Power interference noise
External interference of audio equipment, in addition to electromagnetic radiation, the introduction of interference noise in the power supply will be another major cause of noise. Due to the joint access of various lighting equipment, power equipment and control equipment, a very serious interference source has been formed.
If the lighting control equipment, air conditioner, motor and other equipment connected in the same power grid will generate spikes and surge circuits on the power line, the ripple voltage of different frequencies will enter the power supply of the audio equipment through the power line. A part of the interference noise cannot be effectively filtered out by the power supply circuit of the audio equipment, and noise will be formed inside the equipment. Especially the high-power equipment in the same power grid that does not meet the requirements of electromagnetic compatibility is the main reason for interference with audio equipment.
4. Ground loop noise
In an audio system, the entire system must be grounded properly and the grounding resistance is less than 4 ohms. Otherwise, the induced charge generated by the device in the acoustic system due to various radiation and electromagnetic induction will not flow into the ground, thereby forming a noise voltage superimposed on the audio signal.
If there is a ground potential difference between the grounding resistances of different devices due to the difference in grounding resistance, or if there is a loop in the internal ground of the system, ground noise will be caused. When two different sound systems are interconnected, there is also the possibility of noise, which is caused by the direct connection of the ground lines of the two systems.
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