Company ProfileCompany CultureCompany RealityBlogCompany AdvantagesJoin Us
The commonly used physical definition of volume is sound pressure volume, measured in dB. However, when defining the noise level of a fan, it is more appropriate to define it based on the noise power emitted by the fan. The commonly used unit for fan noise is Db (A).
Method of noise testing: According to ISO 3744, ISO 3745, ISO 7779, CNS 6753, JIS 8346 testing specifications. Place the fan in a quiet room with a background noise of less than 15 decibels, as shown in the figure, at a distance of 1 meter from the noise meter. Wait for the fan to operate in free air, measure the suction surface of the fan, and use a sound collection device to collect the measured data and draw a trend chart of the data and sound pressure level.
Noise testing
Noise Test
The following guidelines provide some reference for fan users to minimize fan noise:
1. System Impedance. The range between the inlet and outlet of a casing accounts for 60% to 80% of the total system impedance, and the larger the airflow, the higher the noise. The higher the system impedance, the greater the airflow required for cooling. Therefore, in order to minimize noise, the system impedance must be minimized.
2. Disturbance of airflow. The disturbance caused by obstacles encountered along the airflow path can generate noise. Therefore, any obstruction, especially in the critical range of air inlet and outlet, must be avoided to reduce noise.
3. Fan speed and size. Due to the higher noise generated by high speed fans compared to low speed fans, it is advisable to try and choose low speed fans as much as possible. A fan with a larger size and lower speed is usually quieter than a fan with a smaller size and higher speed when delivering the same air volume.
4. Temperature rise. 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 significantly 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 can also be reduced.
5. Vibration. When the weight of the entire system is very light or the system must operate in a specified way, it is particularly recommended to use soft insulation equipment to avoid the transmission of fan vibration.
6. Voltage fluctuations. The higher the voltage applied to the fan, the greater the vibration and noise generated as the speed increases.
7. Design considerations: The design of each component that constitutes a fan will affect the level of noise. The following design considerations can achieve noise reduction: the size of the winding iron core, the design of the fan blades and outer frames, and precise manufacturing and balancing.
Attach basic knowledge related to noise：
Decibel, abbreviated as dB
We all know that Bell invented the telephone in 1876, but what is important is that he discovered that the response of our human ears to sound intensity is logarithmic, which roughly means that when the intensity of sound increases to a certain level, people's hearing becomes less sensitive. This allows the unit of logarithm to represent the characteristics of the human ear. To commemorate his discovery, he named Bell.
When Bell is used for long-distance calculations, it is OK because the unit of Bell is too large in practical applications. When we use it for small signals, we need to further subdivide it into tenths as a unit. Just like when you want to measure a small voltage when using an electricity meter, it will automatically cut down one grid, which is called decibel. From the English word, decibel is (one tenth), (decimal) is decimal, abbreviated as "decimal", and "decimal+bel" is called "decimal", And here is the abbreviation for dB. Note that the d before dB is lowercase and the B after it is uppercase. What is the definition of noise unit dB (A)? Is there dB (B), dB (C), etc. What are the differences in the application of these units. According to the explanation of noise, dB is decibel. The A in () represents the weight, which is weighted within the audible range of 20-20K Hz. Within (), B is very rarely used, C represents measurement of machinery and equipment, G represents ultra-low frequency, and D represents aviation noise. These are all differences due to the different sensations that sound gives people. The most common one is (A).
The human ear has different sensitivities to different frequencies, hence the concept of weighted sound levels. Taking the "A" weighted sound level as an example, the sound pressure level value will be reduced according to the formula before adding the low frequency and high frequency sound pressure level values together. The unit of the value obtained by adding the sound pressure level values together is decibels (A). Decibels (A) are 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. Weak noise has a lower decibel/decibel (A) value.
The sensitivity of the human ear to sound depends on the frequency of the sound. For sounds ranging from 2500 Hz to 3000 Hz, the human ear has the most sensitive response, while for low-frequency sounds, its sensitivity is lower.