Cooling fan noise test and the best way to reduce fan noise

Cooling fan noise test A commonly used physical volume definition method is the sound pressure volume, in dB. However, when defining the amount of fan noise, it is more appropriate to define the noise power emitted by the fan. The general fan noise unit is Db(A). Noise test method: According to ISO, ISO, ISO, CNS, JIS test specifications. As shown in the figure, place the fan in a silent room with background noise lower than decibels, at a distance of meters from the noise meter. After the fan is running in free air, measure the suction surface of the fan, and collect the data through the sound collection device. And draw a trend graph of data and sound pressure level. The following guidelines provide fan users with some references to reduce fan noise to a minimum:. System Impedance. The range between the air inlet and outlet of a chassis accounts for% to% of the total system impedance. In addition, the greater the airflow, the higher the noise. The higher the system impedance, the greater the airflow required for cooling, so in order to minimize noise, the system impedance must be minimized. . Disturbance of air flow. The turbulence caused by the obstacles encountered along the airflow path can generate noise. Therefore, any obstacles, especially in the critical air inlet and outlet areas, must be avoided to reduce noise. .Fan speed and size. Since high-speed fans produce more noise than low-speed fans, you should try and choose low-speed fans as much as possible. A fan with a larger size and a lower speed is usually quieter than a fan with a small size and a higher speed when delivering the same air volume. . The temperature rises. In a system, the air volume required for cooling is inversely proportional to the allowable temperature rise. Allowing a slight increase in temperature rise can greatly reduce the required air volume. Therefore, if the restrictions imposed on the allowable temperature rise are slightly relaxed, the required air volume will be reduced and the noise will also be reduced. .vibration. When the weight of the entire system is very light, or the system must operate in a certain manner, it is particularly recommended to use soft insulation equipment to avoid the transmission of fan vibration. .Voltage changes. The higher the voltage applied to the fan, the greater the vibration and the greater the noise due to the increase in speed. .Design considerations The design of each part of the fan will affect the noise level. The following design considerations can achieve noise reduction: the size of the winding core, the design of the fan blade and the outer frame, and the precise manufacturing and balance. Attach the basic knowledge of noise. Decibel (decibel) is abbreviated as dB. We all know that Nian Bell invented the telephone. However, what is important is that he found that our human ears respond to sound intensity in logarithmic form, which roughly means when sound is sound. When the intensity increases to a certain level, the human hearing will become less sensitive, which allows the logarithmic unit to be used to represent the characteristics of the human ear. In commemoration of his discovery, it was named Bell. Bell is ok when used in long-distance calculations, because the Bell unit is too large in practical applications. When we use it for small signals, we must subdivide it by tenths as a unit, just like you are using When the meter wants to measure a small voltage, it will automatically go down and cut a grid similarly, this is decibel (decibel), from the English word decibel is (tenth), (decimal) is decimal, abbreviated as deci, change deci +bel becomes decibel, and this has the abbreviation dB. Note that the d in front of dB is lowercase and the B behind it is uppercase. What is the definition of the noise unit dB(A)? Are there dB(B), dB(C)...etc. What are the differences in the applications of these units? According to the explanation of noise, dB is decibel. The A in () represents the weight, which is weighted in the audible range of human ears K Hz. In (), B is very rarely used, C represents the measurement of machinery and equipment, G represents ultra-low frequency, and D represents aviation noise. These are all differences due to the different feelings of the sound. The most common is (A ). The human ear has different sensitivity to different frequencies, so it brings out the concept of weighted sound level. Taking the'A' weighted sound level as an example, the sound pressure level value will be reduced according to the formula before the low frequency and high frequency sound pressure level values u200bu200bare added together. The unit of the value obtained by adding the sound pressure level values u200bu200btogether is decibel (A). The decibel (A) is more commonly used because this scale can more accurately reflect the human ear's response to frequency. Louder noise has a higher decibel/decibel (A) value. For weaker noise, the decibel/decibel (A) value is lower. The sensitivity of the human ear to sound depends on the frequency of the sound. For the sound from Hertz to Hertz, the human ear responds most sensitively, while it is less sensitive to low-frequency sounds.