Sound Level Calculation

[sfxf]

In the project I am working on, the sound level of the fan is known, and the end of the duct is 50 ft away from the fan. I want to find out the sound level at the end of the duct. Is there any formula to calcuate this? Does the same formula apply to the piping system sound calcuation?

Thank you for help.

 

[3b2]

Fan noise will be attenuated to some degree through the duct. What kind of duct and fittings exist in the run makes a great difference in the amount of attenuation. Unlined duct gives a minor reduction to sound. More is found in the ASHRAE Fundamentals(1997), Ch.7, and Applications(1995), Ch.43.

3b2