Author Topic: House next to motorway - Coincidence gap and window vibration  (Read 3531 times)


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I have old wooden windows on a old weatherboard house backing on to a motorway with in New Zealand. Unfavourable noise and vibration is experienced.

I am looking to first replace with double glaze inserts given the poor condition of current windows (and for thermal reasons.) Then if sound still a problem my plan is to secondary glaze with a large air gap.

The insert manufacturer can only make up to 32mm so the 2 best options I can see are as follows.  Can you please rate their effectiveness or suggest any other alternative configurations:

A.) 6.38mm laminate, 20mm gap, 4mm float
B.) 10mm float, 16mm gap, 6.38mm laminate.

My largest proposed window is 1.7M x 1.3M - is there any concern that with heavy option B the window may visibly vibrate? In its current format that area of glazing is made up of two separate windows.

I was also wondering if the coincidence gap is likely to be an issue with option B making it not recommended?

Can you confirm the thickest glass should always go on the outside?

Randy S

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Re: House next to motorway - Coincidence gap and window vibration
« Reply #1 on: May 04, 2017, 03:11:47 PM »
You have a couple issues,
First, the size of the window is quite large and therefore already a good speaker for vibration so any application you do is not going to deliver the best value of reduction.
second, your gap size is to small for optimal sound reduction.

So in your case I would go with option B as you posted just for the sheer mass of the overall system.

If you could increase your gap size to 50mm you would quite a substantial value of reduction.

Randy S.