Helmholtz resonator Actual sizing ??? 1

[jeyaselvan]

I am designing a Helmholtz resonator for reducing the intake noise of screw compressor. As put forward by Mr.Rob45 in earlier threads on similar subjects, no reference has been given in text books available for actual sizing. I initiated the design such that the product of resonator volume(in cubic inches) and frequency (in Hz) shall be around 18000-20000. Is there any other way to estimate the transmission loss of Helmholtz resonator?

In screw compressor through a detailed sound intensity analysis,we observed that the first harmonic of the lobe meshing frequency is dominant in the intake side of compressor. For a case which I have been designing, the resonator is being designed for a frequency of 538 Hz ( the fundamental frequency being 269 Hz).

However I am unable to achieve reasonable attenuation in the design. Typical numbers of my current design are
Intake section dia : 100 mm
Resonator length :130mm
Resonator dia : 75mm
Throat dia :50mm
Throat length : 13mm
Any tips / suggestions ???

 

[GregLocock]

That throat length/dia ratio is all wrong. I suggest you get an acoustics book and learn about the theory rather than plugging numbers into a formula. Plug'n'chug may be OK for the bridge designers, it doesn't work in acoustics.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[jeyaselvan]

Thank you Mr.Greglock. Could you please suggest some titles on fundamentals of acoustics?

 

[SomptingGuy]

http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471847380.html

It's not a "fundamentals" book, but it's the bee's knees for intake & exhaust acoustics.

 

[Rob45]

For 538 Hz, you might well be better off with a series of quarter-wave tubes, or even the modified Herschel-Quincke tube.
With the latter, you'd have broader-band attenuation, with the former you'd have simple and cheap.