123ArticleOnline Logo
Welcome to 123ArticleOnline.com!

ALL >> Others >> View Article

Ventilator Noise Problems

By Expert Author: Oleg Chetchel

Phenomena of both sound and vibration are very similar and related. The term “sound” is used for air or other gas while “vibration” is used for a similar disturbance of motion in a solid. The sound pressure disturbance impacting on a solid can impart a vibration while the vibration of a solid can result in sound. Some prefer to call the concept of vibration which results in sound “structure borne noise.”

There are two types of noise problems — those that we anticipate from our sound ratings and those emanating from some abnormal condition in the fan. Some of the more common sources of abnormal or unanticipated noise are:

1) Fan wheel unbalance.
2) Resonance of fan or attached components.
3) Rotating components rubbing on stationary parts.
4) Failing, misaligned, or contaminated bearings (on the fan or on the motor).
5) Air leakage. This can allow sound leakage and also generate a whistle-type noise.
6) Belts slipping.
7) Coupling misalignment.
8) Motor noise, especially with improper power supply. Inverter drives may increase motor noise at certain speeds.
9) Air turbulence.
10) Operation in surge.
11) Loose components.
12) High velocity air blowing over fixed components which are not part of the fan.

The other class of noise problems are those we have anticipated because of normal fan sound ratings. Some cures for these problems are:

- Select a different fan. Computerized selection routines allow us to examine many fan types looking for the quietest. Use a custom fan design, if required.
- Relocate the fan to where sound is not a problem.
- Vibration isolation and flexible connectors on the inlet and discharge will reduce structure-borne noise.
- Insulate or acoustically enclose the fan housing if housing radiated noise is a problem.
- Add silencers or duct lining to inlet and / or discharge to reduce sound in these directions. However, a silencer on the outlet does not reduce the housing radiated noise or inlet noise; and an inlet silencer does not affect the housing radiated and/or outlet noise.
- Look for ways to reduce system resistance since sound output is proportional to fan static pressure.

One final tip which can help to avoid noise problems is to select lower RPM fans. Fans exceeding 3000 RPM are much more likely to tune in to an attached structure resulting in structure borne noise. Structure borne noise easily propagates an entire system and can become a problem at many locations. Also, people tend to become more annoyed with higher frequencies than with lower, increasing the likelihood of a noise problem.

Recently, several changes are developing in the technology of fan noise. Some of these are:

1. The latest codes define testing for fan inlet noise, fan outlet noise, and noise radiating from the housing (or casing). The inlet noise can no longer be assumed to apply to the outlet and vice-versa.
2. A new test code which uses sound intensity is near adaption. In theory, integrating a series of measured sound intensities over an enclosed area yields the sound power directly.
3. Sound criteria is playing an ever more important role in the selection process. Many fans are insulated for sound or use other sound reduction apparatus.
4. Active noise cancellation continues to be difficult to apply to most fan installations. If it ever proves practical, this technique can cancel fan noise by adding a second pressure wave out of phase with the original.
5. Many more fan specifications are requiring AMCA sound certification. Certified sound ratings mean that AMCA has verified that the ratings are generated in accordance with the codes and that at least one sample has been tested in the AMCA Laboratory to verify the ratings.

For additional information please refer to http://www.northernindustrialsupplycompany.com/outside/request4.html

Oleg Chetchel
Industrial Process Equipment Engineer
nis@primus.ca
Northern Fan Co.
http://www.northernindustrialsupplycompany.com/outside/request5.html
http://www.northernindustrialsupplycompany.com/outside/request3.html

Total Views: 51Word Count: 602See All articles From Author

Others Articles

1. Download Forex Robot To Enjoy Guaranteed Returns On Your Forex Trading Practices
Author: johnsyanol

2. Why Should You Consider Going For Voyage Humanitaire?
Author: James Fidler

3. Web Hosting
Author: zolute

4. Get Pleasure Along With High Profile Kolkata Call Girls
Author: Prachi Rai

5. Make Cheers With Sensible Call Girls Of Kolkata
Author: Prachi Rai

6. Using The Certified Acceptance Agent Services For Itin Issuance And Tax Accounting Services
Author: Robin Joe

7. Innovative Medical Packaging And Enclosures By Intertrade Industries Featured At Mdm West
Author: 1888 PressRelease

8. Individuals Responsible For The Tax Reportings Need To Follow The Guidelines To Apply For An Itin
Author: Robin Joe

9. Importance Of Conveyor Belt Supplier
Author: Anil Gupta

10. Hurry Up To Enroll With Projecturf For Better Project Management.
Author: LincolJalek

11. Have Some Ultimate Pleasure With Independent Call Girls In Kolkata
Author: prachi rai

12. Usability Of Bike Boxes
Author: Brian Miller

13. Process Of Tax Preparation For Cross Border And Filing Of Taxes
Author: Robin Joseph

14. Get Your Answers To Mobile Phone Encryption Queries
Author: Minh Vo

15. An Overlook About Scheduled Tasks With The Help Of Projecturf
Author: LincolJalek


Login To Account
Login Email:
Password:
Forgot Password?
New User?
Sign Up Newsletter
Email Address: