Noise Measurement Method for Fans and Roots Blowers
1. Introduction
GB/T 2888-91, Noise Measurement Method for Fans and Roots Blowers, serves as a national standard issued by the China State Administration of Quality Supervision, Inspection and Quarantine in August 1991. This method was created to insure uniform noise measurement method in relation to fans and rotary positive displacement blowers. The document provides information regarding a fan or blower’s sound pressure level, which is an indication of the amount of noise given off by the device, as well as instructions for accurately measuring and calculating sound pressure levels.
2. Types of Fans and Blowers
There are two main categories of fans and blowers covered by GB/T 2888-91. The two categories are directional fans and root blowers.
Directional fans are air-handling devices that deliver air streams at an adjustable angle. Directional fans are commonly used in industrial settings for heat transfer, ventilation and exhaust.
Roots blowers are also known as Positive displacement blowers, where an impeller rotates in a cavity to create suction, leading to a positive displacement of air forward. The roots blower is used to transfer air and other gases, such as generation of vacuum.
3. Sound Pressure Level Measurement
The sound pressure level of a fan or blower is a representation of the sound given off by the device. In order to measure this value, a microphone and a sound pressure level meter will be used. The microphone and sound pressure level meter must be placed in position to accurately measure the sound pressure level given off by the fan or blower.
The sound pressure level given off by the fan or blower needs to be converted into sound pressure level in A-weighted decibels (dB(A)). To do this, the sound pressure level (in dB) will be divided by 10 and then subtracted from the A-weighted decibel value. This calculation should be carried out for each frequency band, using the results for all frequency bands combined to give a value for the A-weighted decibel value.
4. Calculations
The sound pressure level during operation can be calculated using the following formula: Lp = 10 log10 [(P0/Pref)2 + (P1/Pref)2 + … + (Pn/Pref)2]
Where Lp is the sound pressure level in dB, P 0 is the measured sound pressure level at frequency 0, Pref is the reference sound pressure level, P1 is the measured sound pressure level at frequency 1, and Pn is the measured sound pressure level at frequency n.
5. Conclusions
GB/T 2888-91 is an important national standard that provides information regarding the noise measurement procedure for fans and rotary positive displacement blowers. The method covers the measurement of the sound pressure level, which is an indication of the amount of noise given off by the device, as well as instructions for accurately measuring and calculating sound pressure levels. The method is based on the use of a microphone and a sound pressure level meter to accurately measure the sound pressure level given off by the fan or blower. The results of the measurements must then be converted into A-weighted decibels to determine the sound pressure level given off by the device.
