Whirling Sound 54dB

[jrrocks]

A completed hospital project. Got a complaint for higher noise level of around 52 dB in staircase , where as acceptable is 45 dB. Cool air supplied through FCU unit. After adjusting flow/vcd, clean filter and all, we didnt got much success. We further analyzed the drawings and found that the FCU flow is more than what is required in design and increased flow rate creating whirling/whistling kind of noise while passing through the grills. But could not able to prove that the noise is due to this reason. Staircase is completely enclosed and silent space. Another stairwell having correct FCU unit as per design, but there also we are facing noise issue. Can anyone advise, what else i could try to reduce the noise, please.

 

[lukaiENG]

it sounds like you may be getting regenerated noise off the grilles or maybe through some torturous duct design. maybe as a test you could remove the grille and see if the noise stops, if it does then you might be able to re-select for a higher free area grille to achieve the same design.

 

[Emrelug84]

Can you please give us a drawing showing all dimensions, all equipments and flow rates? First, you need to analyze the design to find noise isuue.

 

[GT-EGR]

You need a full sound profile - 52 dB in which octave band? Once you find the octave band that is coming in too high it is easier to troubleshoot.

You also need to know the inlet discharge and radiated sounds levels of the equipment specified - and compare it to your maximum allowable sound levels - this will tell you if it’s an install problem or if the wrong equipment was ordered from the start

In these situations you’re likely best method of sound reduction is reducing the fan speed/airflow. If it’s a low octave band maybe it’s vibration, a high octave band maybe you have an undersized grill. Attenuators can help, but you need to get your equipment sounds levels so you know where the sound is coming from (inlet discharge or radiating) and you know which octave bands you have to reduce the sound levels from.

 

[jrrocks]

Thanks to all. I will try out the activities mentioned herewith. Will respond back the results.

GT-EGR
52 dB is measured with handheld Sound Level Meter. NC measurement were not carried out.

 

[GT-EGR]

Checkout this link

https://www.google.com/amp/s/

http://www.engineeringtoolbox.com/amp/nc-noise-criterion-d_517.html

Decibel measurement is associated with a specific frequency. So your meter is likely at a specific frequency to get you 52. And if you adjust the frequency you’ll get different dB measurements.

52 at low frequency isn’t bothersome, 52 at high frequency can be

 

[itsmoked]

Reminds me, I walked into a pizza parlor last night to pick up a pizza. It was very bothersome, actually painful.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[berkshire]

With noise issues with return air grilles, sometimes taking the grille back to the shop and steepening the angle of the louvres, will quieten them down a little, It may not help in your case , but it is worth a try, what do you have to lose?
B.E.

You are judged not by what you know, but by what you can do.