What test conditions need to be stated for air conditioning box noise data?

The noise data of the air conditioning box should indicate the operating air volume, pressure, speed, configuration, measurement indicators, measurement points or methods, and background environment. If the report does not indicate whether the test object is a complete machine, an air outlet, or a separate fan, or does not indicate the weighting method, it should not be directly used as a basis for comparison under the same conditions.

First check whether the report can restore the test scene

The status of the filter, the position of the air valve, whether the air duct is connected, and whether it contains a silencer section may all affect the results. Sound pressure measurements also need to account for distance, orientation and environment; sound power needs to correspond to the method and boundaries used. When the total values ​​are close, the sub-band characteristics may still be different, which has different meanings for subsequent noise reduction design.

The operating conditions should include air volume, pressure, rotation speed and configuration of major components; the measurement conditions should include acoustic indicators, weighting, frequency bands, methods or measuring points; the environmental conditions should include background noise, connecting air ducts and on-site acoustic environment. The three types of conditions correspond to different influencing factors, and missing one may cause the numbers to lose comparability. For the difference between sound power level and sound pressure level, please refer toHow to distinguish the sound power level and sound pressure level of air conditioning box?。

Operating conditions must correspond to noise data

The same air conditioning box may have different noise levels under different air volumes, pressures and rotation speeds. The fan speed, air volume, external static pressure and filter status during the test should be noted in the report. If you only write 'rated operating conditions' without giving specific parameters, it will be difficult to judge whether they are at the same operating point during comparison.

For the relationship between fan operating point and noise, please refer toWhy should we check the efficiency range when selecting air-conditioning box fans? . Different pressure calibers will also affect the description of working conditions, please refer toWhat is the difference between static pressure, total pressure and static pressure outside the air conditioner box?。

Is the test object the whole machine, the air outlet or a separate fan?

Noise data may come from the entire machine, air outlet, fan section or individual fan. The data of the whole machine includes box radiation and airflow regeneration noise, the data of the air outlet is closer to the entrance of the air supply pipe, and the data of the individual fan only reflects the fan itself. The values ​​of the three types of objects cannot be directly compared, and the test boundaries should be clearly stated in the report.

Fan type comparison will also affect the noise, please refer toHow do the backward-inclined and forward-inclined fans compare when used in air conditioning boxes? . For the influence of box structure on radiated noise, please refer toWhat are the differences between double-layer box boards and single-layer box boards used in air-conditioning boxes?。

Sound pressure level must indicate distance and environment

The sound pressure level changes with the distance of the measuring point, room sound absorption and background noise. The report should indicate the distance, orientation, height and acoustic environment of the measuring point. If the background noise is high, the uncorrected reading may be too high; if the measuring point is close to a reflective surface, the reading may also be affected. Sound pressure values ​​at different distances cannot be directly compared.

How the noise propagation path affects on-site experience can be referred toWhat noise propagation paths should we pay attention to when selecting an air-conditioning box? . If the project has noise requirements for the computer room or work area, it should be evaluated by acoustics or system design combined with the propagation path, and cannot be judged based on just a numerical value in the equipment sample.

The weighting method and frequency information must be written clearly

The total A-weighted value is suitable for general acoustic evaluation, but low-frequency components may be weakened under A-weighting. If the project is sensitive to low-frequency noise, sub-band data should be viewed. The report should indicate whether A-weighting, C-weighting, or linear weighting is used, and whether octave or one-third octave data are provided.

Frequency information has practical significance for muffler selection and propagation path analysis. Given only one A-weighted total value, it is impossible to determine the main frequency components of the noise, and it is also difficult to compare the control effects of different solutions on specific frequency bands.

How to obtain comparable information from different suppliers

Include the same set of working conditions and required acoustic indicators in the inquiry document, and be required to indicate whether the data source is measurement, calculation or selection software. If the project requires on-site verification, the measurement location and environmental responsibilities should be clarified in advance. Sound pressure values ​​at different distances or results under different air volumes cannot be judged by simply arranging numbers.

How to list applicable standards in procurement technical documents, please refer toWhat applicable standards should be listed in the technical documents for purchasing air-conditioning boxes? . How to unify the caliber of the inquiry form, please refer toHow to write an inquiry form for air-conditioning boxes so that different quotes can be compared?。

Aili industrial supporting equipment

When checking the noise requirements with Aili Industrial, the measurement boundaries specified by the project can be given first to facilitate confirmation of equipment side data and parts that need to be evaluated by the system side. Aili's industrial manufacturing end covers independent research and development and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The fan working point, box structure and acoustic data can be matched in the same package; non-standard configurations can provide noise data corresponding to working conditions according to project requirements.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific noise data, test conditions and delivery scope still need to be verified based on the corresponding configuration data and on-site working conditions. The actual effect is subject to on-site measurement and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

There is only one dB value on the sample. Can it be used to compare different manufacturers?
uncertain. It depends on the test object, working conditions, distance, weighting method and method corresponding to the value. The conditions are different and cannot be compared directly.

Which sound pressure level or sound power level is more suitable for program comparison?
Sound power level is more suitable for comparing the sound source itself, while sound pressure level is closer to the experience at a specific location but is greatly affected by the environment. The two should be used together.

Can Aili Industrial provide noise data corresponding to working conditions?
Equipment-side acoustic data corresponding to working conditions can be provided according to project requirements. Specific indicators and test conditions must be confirmed based on product information and project agreements.

Related articles

1. How to distinguish the sound power level and sound pressure level of air conditioning box?

2. What noise propagation paths should we pay attention to when selecting an air-conditioning box?

3. How do the backward-inclined and forward-inclined fans compare when used in air conditioning boxes?

4. What are the differences between double-layer box boards and single-layer box boards used in air-conditioning boxes?

Key points for selection and acceptance inspection