Analysis of the reasons for noise in audio applications

In audio systems such as recording and live sound amplification, the noise problem is a ubiquitous and very headache problem. Generally, the more devices that make up the sound system, or the longer the transmission distance, the greater the background noise of the system, and even the sound system cannot perform normal recording or sound reinforcement. The mechanism of sound system noise formation is relatively complicated. Now we mainly analyze and discuss the main causes and solutions of noise in these sound systems.

Cause of noise

1. Electromagnetic radiation interference noise

Spurious electromagnetic radiation interference in the environment, such as high-frequency electromagnetic radiation interference of communication equipment such as mobile phones, walkie-talkies, elevators in the surrounding environment, air conditioning, automobile ignition, electric welding and other electrical pulse radiation, lighting control of the studio using thyristor rectifier control equipment The generated radiation is directly mixed into the transmission signal through the audio transmission line to form noise, or the casing of the poorly shielded machine equipment interferes with the internal circuit to generate interference noise. Practice has shown that in some special occasions, such as the large number of studios using thyristor dimming equipment, if reliable shielding and grounding measures are not taken, the noise will be very serious.

2, power interference noise

External interference of audio equipment, in addition to the electromagnetic vehicle radiation mode, the introduction of interference noise in the power supply part will be another main cause of noise. The urban power grid has formed a very serious interference source due to the joint access of various lighting equipment, power equipment and control equipment. If the lighting control equipment, air conditioner, motor, etc. connected in the same power grid will generate spikes and surge currents on the power line, the ripple voltage of different frequencies will enter the power supply of the audio equipment through the power line. Some 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.

3, 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 audio system due to various radiation and electromagnetic induction will not flow into the earth, 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.

4, the circuit noise inside the device

Audio equipment has an indicator - signal to noise ratio. Due to the electrical noise generated by internal electronic components, the required specifications can be achieved when a single device is working alone, but when multiple devices are cascaded, the noise accumulates. In practical applications, some low-end civilian 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.

A. Mixer Beater (s/s)

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C. Potato masher

D.550ml measure cup

F. 700ml measure cup

G.350ml chopper

H.700ml Chopper with non-slip base

I. Fine slicer & Julienne Disc, Rough slicer & Julienne Disc, Shred Disc.(For 700ml chopper use only)

J. Knife Sharpener

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