how to calcualte noise level

Your best bet is to contact the fan manufacturers and ask them for the noise rating.

I doubt very much whether there is a simple set of formulae to calculate a noise figure. As it would be entirely up to the type of fan used, the geometry of the blades, type of motor, etc...

John.

Dear electromen,

fan is cetrifugal fan.blade is backward curve and rpm is 1440 motor is tefc sq cage induction motor.these are the information.pls explain how to calculate noise?

Anything you do by calculation would be just a guess. To be accurate you need something like this:

http://www.newark.com/22H6407/test-measurement-equipment/product.us0?sku=TENMA-72-860A

Real data can't be argued with.

You CAN'T calculate the noise level...!

You can measure it... or you can guess...but you can't calculate it.

Del

can be calculated .some octave bond frequency and stifness are playing roll to calculate the sound level with the accuracy of

+or - 5%

I'm sorry but I think that is nonsense...
The very environment which a system is will effect the sound pressure level.

We are talking about a fan.... just conside the effect of placing the fan in a duct.

If you have a very well defined and closely controlled system with a decent amount of empirical data then you may possibly calculate the effect of small changes.

Unless you specify test conditions then any calculation will be worthless.

Otherwise I'm sure that one can do a calculation but it won't be of any use.

Del

You can directly measure the sound level using a sound level meter. Came across a good model.

http://www.industrialindia.com/catalogs/Portable_Digital_Sound_Level_Meter/Portable-Digital-Sound-Level-Meter-HTC-1350.pdf

Very complex. What are you trying to achieve? See knrforensic.com

You can't calculate noise level directly. You have to measure it at a specified distance, then add in the background noise level to get the final answer. And no, you cannot add the 2 noise levels arithmetically as they are measured logarithmically. You can get the equations involved at this website: http://en.wikipedia.org/wiki/Decibel.

my dear dvader,

i am asking doubt on sound pressure calculation on fan while designing a fan .in our company we have one soft ware in that soft ware ,if we giving the octave bond frequncy of rotor in various tip speed point and stiffness the sound pressure levels comes with a accuracy of +or- 5%. while i check the result after running of fan with sound level meter result are almost equal to designed value. my question is is any emperical formula is available for calculate sound level?