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Old 16th January 2013, 04:22 AM   #1
tnargs is offline tnargs  Australia
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Default Soundwave theory question: reflection

Hi, is anyone able to help me grasp a particular question please.

If a 300mm (1 foot) diameter column is pressed up against the front of a loudspeaker (or just clear) ----

1--- which wavelengths reflect straight back to the speaker?

2--- which wavelengths are scattered widely?

3--- which wavelengths are relatively unaffected and pass right around the column?

4--- is there a transition region between 2 and 3 and if so, what happens in it?

I would like to better understand the relationship between deflector size and sound wave behaviour.

Thank you
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Old 16th January 2013, 04:55 AM   #2
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How big is the driver?
There is open source software to model this at
AcouSTO - Acoustics Simulation TOol - Homepage
but not easy to use
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Old 16th January 2013, 11:22 AM   #3
tnargs is offline tnargs  Australia
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Well it is an in-principle question, so I will take any driver size you care to assume. thanks
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Old 16th January 2013, 11:23 AM   #4
tnargs is offline tnargs  Australia
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I haven't seen that tool before. I will take a look.

Any generalised answers would also be much appreciated.
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Old 16th January 2013, 06:54 PM   #5
Ron E is offline Ron E  United States
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I think you will find that this is much easier to measure than calculate, and it depends on your observation point. Probably the best way to resolve this qualitatively is with a java ripple simulation calculator - do a search.
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Old 16th January 2013, 07:10 PM   #6
tnargs is offline tnargs  Australia
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Thanks Ron, I'll have a look.

I wonder if there is a general rule like "if the wavelength is more than twice the column diameter, there is little to no scatter of the sound"?
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Old 16th January 2013, 10:42 PM   #7
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The behaviour of a plane wave passing your column is fairly easy to predict. You have a far more complex situation as the column is close to the source and gives early reflection back to the driver
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Old 18th January 2013, 10:27 PM   #8
Ron E is offline Ron E  United States
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Quote:
Originally Posted by tnargs View Post
Thanks Ron, I'll have a look.

I wonder if there is a general rule like "if the wavelength is more than twice the column diameter, there is little to no scatter of the sound"?
It's probably closer to 6 times...
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Old 19th January 2013, 03:14 AM   #9
tnargs is offline tnargs  Australia
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Thanks Ron and David, I will continue to study it.
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Old 19th January 2013, 10:59 PM   #10
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Would a Hornresp simulation throw out anything useful?
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