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Helmholtz resonator: absorber or source
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March 26, 2018 - 3:45 am
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Hello,
I always have been reading on books that Helmholtz resonators are great absorbers on a small frequency range. Its effect is given by the air inside the box which is acting like a spring and the dissipation of energy comes from the “neck” of the box. So basically mostly say it is similar to a mass-spring system but I would say that this can be thought like a mass-spring system with a dumper (neck effect).
Well, then I also found on books that Helmholtz resonators are very common in our life. A bottle is a very simple Helmholtz resonator. If you blow into it with its natural frequency the resonator will resonate making a sound with the frequency of its first mode.
So here my curiosity: I m not able to see the Helmholtz resonator like something that reduce the energy into the room since when it is forced by its resonant frequency it starts to sound increasing the sound.
Is there anyone which can solve my doubt? :)
Thank you

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March 26, 2018 - 8:01 am
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X, Helmholtz resonators are frequency specific. Once you have designed for a given frequency, you know that frequencies above the designed for resonant frequency will be absorbed and those below will not.

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March 26, 2018 - 4:15 pm
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Thanks for the reply but I still don’t get it. As far as I have understood even A.Everst in his book spilts H. resonators in two categories. Those to absorbe the sound and those to raise the RT (this one was also used in ancient Greek theaters).
Still in dobut! :)

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March 27, 2018 - 7:56 am
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X, There are three types of low-frequency absorption technologies: membrane, diaphragmatic, and Helmholtz. Each has pros and cons for performance, build, and space requirements.

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