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Old 25th April 2005, 11:38 AM   #1
keyser is offline keyser  Netherlands
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Default vent-design

hi all!
I've been looking at the formulas for a while, but I still don't get it completely. Could anyone tell me what the effects to Fb are, when you make the port longer, increase width, or increase the number of ports.
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Old 25th April 2005, 12:05 PM   #2
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Longer vent = lower Fb
Wider vent = higher Fb
More vents = wider vent = higher Fb

The wind noise is dependent on the frequency of Fb and the diameter of the vent. Lower tuning makes less noise. Wider vent makes less noise.
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Old 25th April 2005, 12:46 PM   #3
keyser is offline keyser  Netherlands
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Thanks!
Quote:
More vents = wider vent = higher Fb
Is this about the total surface area of the vent? two 10 cm^2 vents amounts to the same Fb as one 20 cm^2 vent?
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Old 25th April 2005, 01:14 PM   #4
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It is about the cross-sectional surface area, but 2x 100mm vents are not the same area as 1x 200mm vent Remember area is Pi * radius^2
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Old 25th April 2005, 03:21 PM   #5
keyser is offline keyser  Netherlands
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I wasn't talking about two 10cm diameter ports, but two 10 cm (square) ports. Guess my assumption was right then, wasn't it?
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Old 25th April 2005, 03:35 PM   #6
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It was correct (maar niet helemaal ),

In practice it can be slightly different because two smaller ports have a different effect on the air in the port as one port has. That's also why rectangular ports have different effects than round ports (a round one would be, again slightly, better).

If I'm not mistaken the newer versions of WinISD (Pro) take this into account. The differences aren't huge but are there.

Mvg Johan
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Old 25th April 2005, 06:29 PM   #7
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Yes, you were right keyser. Sorry.
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