Why are FFU noise data different? How ranging, working conditions and environment affect the results
Why are the noise data of the same FFU different?
In FFU selection and parameter comparison, noise is an indicator that is often concerned. However, many projects will find that the noise data measured by the same FFU in different materials or at different sites are inconsistent. Sometimes the differences are so obvious that it's hard to tell which data is more reliable.
When the noise data is different, it is usually not the equipment itself that has changed, but the measurement conditions. Ranging range, operating speed, filter configuration, background noise, measurement environment and instrument status all affect noise readings. If the test caliber is not unified, noise data from different sources will not be comparable.
Aili Industrial will explain the noise test conditions during the FFU complete machine testing and parameter compilation to help project parties make comparisons under the same caliber. For the basic structure of the FFU machine, please refer toAili Industrial FFU fan filter unit。
How ranging and point location affect noisy data
Noise attenuates with distance. The closer you are to the FFU, the higher the measured noise is typically; the further away, the lower the noise. If the distance marked in one document is 1 meter and in another document it is 1.5 meters, the two data cannot be directly compared.
The direction of the measuring point also affects the results. Noise readings may differ when measured directly below the FFU, to the side, or at an angle. The propagation of fan and airflow noise is directional, and the measurement results are different between the side facing the air outlet and the side facing away from the air outlet.
The height of the measuring points also needs to be unified. The results will be different whether it is measured near the FFU air outlet or at the height of personnel operation. For cleanroom projects, personnel are typically concerned with noise at the operating location rather than immediately adjacent to the equipment.
Therefore, when comparing FFU noise data, you should first confirm whether the distance measurement, measurement point direction, and measurement point height are consistent.
How operating speed and filter status affect noise
The noise of FFU is directly related to the operating speed. The higher the rotational speed, the louder the fan and airflow noise is. If one piece of data is measured at rated speed and the other is measured in low-speed mode, the two cannot be directly compared.
Filter status also affects noise. After the filter resistance increases, the fan operating point changes, and the noise may change accordingly. The noise of a new filter and a dust filter may be different. The noise data will also be different if the filter is installed or not, the filter efficiency level and the resistance are different during the test.
For FFU using group control or speed regulation, the noise data should indicate the corresponding speed or control setting. Regarding the impact of control methods on operating status, please refer toFFU/EFU group control touch screen controller to understand different control schemes.
How environmental background noise affects results
The noise measured is the total sound pressure level, including FFU noise and environmental background noise. If the background noise is high, the measured noise data may be inflated by the background noise. If the background noise is low, the noise of the FFU itself is more likely to be accurately reflected.
When measuring on-site in a clean room, there may be other FFU, air conditioning equipment, process equipment and personnel activities in the surrounding area, which will contribute to background noise. The noise data of a single FFU is different from the room noise when multiple FFUs are running simultaneously and cannot be substituted for each other.
If you want to compare the noise of a single FFU, it is recommended to measure in an environment with low background noise, or correct the background noise according to standard methods. If room noise is to be evaluated, it should be measured under actual operating conditions and the number and status of equipment operating simultaneously should be recorded.
What is the difference between single unit noise and room noise?
The noise of a single FFU describes the noise level of a single device under specific conditions. Room noise describes the actual noise environment at personnel or process locations when multiple FFUs and other equipment are operating simultaneously.
When multiple FFUs are running at the same time, noise will be superimposed. If FFUs are densely arranged, the room noise may be significantly higher than the noise of a single unit. In addition, reflections, absorption and structural propagation within the room also affect the actual noise. Ceilings, walls, equipment and people will all change the sound field distribution.
Therefore, the noise data of a single FFU is suitable for equipment comparison, but it cannot directly represent the room noise after installation. When assessing noise in a project, these two levels should be distinguished.
How to unify the noise comparison caliber
To uniformly compare the noise data of different FFUs, it is recommended to confirm the following conditions: ranging and measuring point direction, measuring point height, operating speed or control settings, whether a filter is installed and filter configuration, background noise level, measuring instrument model and calibration status, whether the measurement environment is an anechoic chamber or on site, and whether a single unit is measured or multiple units are operated.
If the manufacturer provides noise data, it can also require a description of the test conditions. If the project requires on-site verification of noise, it is recommended to use the same instrument, the same range and the same operating status for measurement.
Issues that should be confirmed in advance during project communication
During the FFU noise evaluation and acceptance stage, it is recommended to confirm the following with the manufacturer: the distance measurement and measurement point location of the noise test; the rotation speed and filter configuration during the test; the background noise level and correction method; the model and calibration status of the measuring instrument; the distinction between single unit noise and room noise; the specific noise requirements of the project; whether on-site noise measurement and recording is required.
If you are doing FFU noise comparison or clean room noise assessment, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also contact Aili Industrial for noise test condition instructions and selection support.
in conclusion
FFU noise data is different, usually from different distance measurement, measurement points, rotation speed, filter status, background noise and measurement environment. When comparing noise data, the test caliber should be unified first and the noise of a single device and the room noise after multiple installations should be distinguished.
Aili Industrial has complete production capabilities in FFU complete machine testing and parameter compilation, and can explain the noise test conditions to help project parties make comparisons under unified conditions. If you need to know more about FFU noise parameters, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.
