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Analysis and Solution of Common Speaker Noise


When using the speaker, you may encounter problems. Sometimes the speaker will produce noise without receiving any sound source, or there will be noise when playing sound files, or even "inexplicable" noise, which is depressing.
However, there are reasons for everything. Of course, noise will not be generated out of thin air. Today, I will briefly analyze several common causes of multimedia speaker noise and bring some simple and easy solutions.
Generally speaking, there must be an amplifier inside the active speaker, so the noise is inevitable, so the statement of "zero noise" is nonsense. The noise of the active speaker can be roughly divided into electromagnetic interference, ground interference, mechanical noise and thermal noise according to the source.
 
Electromagnetic Interference:
Electromagnetic interference can be divided into power transformer interference and stray electromagnetic interference. In general, multimedia speakers usually use EI type, ring type or R type transformer.
For low-end products, EI-type transformers are most widely used. The air gap between E-and I-type cores and the self-radiation of coils are the main sources of magnetic leakage. Moreover, the magnetic leakage of this transformer is also directional. The interference in the Y-axis direction is the strongest and the Z-axis direction is the weakest. Therefore, we can observe which plane the sound box circuit board is placed parallel to, thus making a preliminary judgment.
 
toroidal transformer:
The toroidal transformer does not have the problem of air gap and coil radiation, and the magnetic flux leakage will be very little in theory. However, this kind of transformer has relatively high requirements for the power supply environment. If the lighting waveform we use is seriously distorted, the effect of using a ring transformer is even worse than that of EI type, so we should also consider the power supply environment in which we are located. The magnetic flux leakage of the R-type transformer is similar to the ring type, and the author will not elaborate here.
After a simple analysis of the reasons, we can solve the problem in a targeted way. When conditions permit, the effect of installing a shielding cover for the transformer is very obvious, which can block the magnetic flux leakage to the greatest extent. The shielding cover can only be made of iron materials. Generally speaking, we should try our best to choose products with big brands and solid materials. If the iron core, copper wire and other materials of the transformer are of poor quality, the iron loss and copper loss of the transformer will be more serious, resulting in an increase in the no-load current of the transformer, so the magnetic leakage phenomenon will be more obvious. In addition, the use of external transformers is also a good way.
 
stray electromagnetic wave and ground interference:
Stray electromagnetic interference is more common, speaker wire, frequency divider, wireless equipment or computer host will become the source of interference. The main speaker in the allowable conditions as far as possible away from the host computer, and reduce the peripheral wireless devices. On the other hand, some customers connect the speaker to the front audio interface of the computer and insert Bluetooth equipment into the USB interface beside it, which will also cause electromagnetic wave interference to a certain extent. If the user does not often replace the audio equipment, it is recommended to insert the audio cable into the interface behind the host.
 
Correct grounding method:
Ground interference is mainly low-frequency signal circuit, high-frequency signal circuit and power supply circuit in the grounding position is not selected when the interference phenomenon of AC sound. Generally speaking, the high frequency uses the ring ground instead of the single wire grounding, while the low frequency follows the principle of independent routing and centralized grounding. In actual use, we are basically not affected by this kind of interference. These grounding methods are basic common sense in circuit design.
 
mechanical noise and thermal noise:
Let's talk about mechanical noise. As the name implies, this noise comes from mechanical movement, and this noise is also unique to active speakers. During the operation of the power transformer, the vibration of the iron core caused by the alternating magnetic field will produce mechanical noise, which is very similar to the hum of the fluorescent lamp ballast. Choosing good quality products is still the best way to prevent this kind of noise. In addition, we can install a rubber damping layer between the transformer and the fixed plate.
 
Potentiometer:
One more thing we should pay attention to, if the potentiometer is used for a long time, the metal brush and the diaphragm will have poor contact due to dust accumulation and wear, and noise will be generated when rotating. If the screws of the speaker are not tightened and the inverting tube is not handled properly, mechanical noise will also be generated when playing large dynamic music.
 
Pay attention to the heat dissipation of the speaker:
Finally, let's talk about the impact of thermal noise on speakers. Because our speakers are the use of resistors, capacitors and transistors, IC, the conductive part of these components there is a large number of free electrons, and as the temperature of the components, the number of free electrons will be greatly increased, the disorderly movement of electrons will be strengthened, this strengthening will be reflected in the tweeter issued by the "hissing" sound.
To deal with this kind of noise, we can replace the low-noise components or reduce the workload of the components. In addition, reducing the operating temperature is also one of the effective methods.
Article summary: In general, the noise problem of active speakers cannot be avoided. Due to the limitation of product structure, some electromagnetic interference is bound to exist, and pay attention to stay away from the radiation source on the placement of the speakers, and do not let the speakers be used in environments where the temperature is too high. In addition, as far as possible to ensure that the use of electricity in a stable place, to the speaker to assign an independent socket can also avoid the appearance of current sound to a certain extent.
 

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