a long winded description follows. Here is a summary: We have both low frequency (20 to 33 cycles per second ) and high frequency (50 to 60 cycles per second) vibrations. The mats cut down the higher frequencies (although they still let enough through to create noise) , but do nothing to block the lower frequency vibrations. The loudness of the noise is created by the rubber mat underneath my hvac unit which is covering the entire surface area of the bottom of the HVAC unit and the floor below - thus amplifying the vibration. The insulation we put in the walls and the ceiling below is working - but it is cutting down the acoustic noise (noise created by compressing air) - but batt or blown insulation does nothing to block or dampen noise caused by structure vibration. The problem can be solved by removing the rubber mats and replacing them with 4 vibration isolators - which are essentailly leg supports with springs - under the 4 corners of the unit. There was a recommendation to suspend the HVAC unit from above. This could be done but is probably not necessary. I will keep you posted on the progress. *************************detail In my quest to understand the physics of what is happening with the my hvac vibration on the second floor of my home under construction, I stumbled data sheet that has some interesting info in it. See http://www.b-line.com/product/PDFLibrary/pipehangers/index.htm. Click on Vibra-Trol and then the Introduction. Download the PDF data sheet. The table on the second page shows the amount of vibration reduction as a function of the deflection of the vibration cancellation device used. If you look at the left most column in the table - the 1/16th inch deflection corresponds to what you get with a rubber mat or neoprene pad. The N/R means not recommended. The HVAC unit we have on the second floor operates in the 1200 to 2000 RPM range (or 20 to 33 cycles per second). If you look at the table you can see that the vibration reduction by a mat/pad in that RPM range is not very good. The Econar units also have a Compliant Scroll compressor. I checked their specs and the unit runs in the 50 to 60 cycles per second range (or 3000 to 3600 RPM). You can see in the table that mats or pads are OK for these higher RPM rates - but not the best. They would still allow 10 to 12% of the vibration through the mats at these higher frequnecies. You also have to consider harmonics - which are additional frequencies generated at +/- 1/2, 1/3,1/4, 1/5 etc of the center frequency of the compressor. If the amplitude of the vibration of the center frequency is high, harmonics at lower frequencies will also be high. That means the harmonics at lower frequencies can also pass through the rubber mats. If you look on the right hand side of the table - you can see what the noise reduction is for spring mounts (you can see an example of one of these on the cover of the attachment - left hand side of the picture with yellow spring and bolt sticking up). A spring device with a 1" deflection provides 97 to 99 percent reduction in vibration for the lower RPM ranges of the fan, the higher RPM range for the compressor, and the harmonics at low frequency created by the compressor. At the bottom of the data sheet - they provide a calculation on how to size the springs based on the weight of the equipment. The corner load is 1.25 times the unit load divided by 4. The spring mounts are not terribly expensive, maybe 10 to 20 dollars each. The springs themselves (depending on the brand) are about 3.5 to 4.5 inches tall with no load, and about 2.5 to 3.5 inches tall when compressed with a load - assuming a 1 inch deflection - which should be adequate for our problem.

How are they planning to mount the laminated glass in the opening? From what I read it will be a more or less permanent mount? One potential advantage (but also potential acoustical disadvantage) of the plastic insert is that it's much lighter than the laminated glass so it can be relatively easy to remove from the opening if necessary, whereas the laminated glass is going to be heavy. A laminated insert using 3mm glass for both lites will be over 50lbs at the size window that you describe, and while laminated glass can be very safe when handling, it's still a chore if you have to remove it from the opening for any reason. But acoustically that weight (density) is to your advantage. The .06 acoustical laminate glass means that they are using a 1.52mm thick PVB interlayer in the laminated glass. Generically .030" or .76mm interlayer is considered safety, .060" or 1.52mm is considered security, and .090" or 2.28mm is considered to be impact resistant, or the thickness generally used for hurricane impact glass. Adding additional thickness also adds some acoustical advantage as well, roughly 1 to 2 dB advantage for every additional .76mm thickness. I would suggest that if you are going to be looking at comparing laminated glass to acrylic, you might consider using the laminated glass in your bedroom.

What is the loft above? If it is above the MBR I would suggest carpet for noise reduction. I personally do not like carpet on stairs. In the past I have had carpet runners on stairs when my kids were little to hopefully lessen injury from falls.

Not sure you would be open to it, but carpet, rather than wood, will help absorb some of the noise from the area. I would try to incorporate your husband's sports decor. It will mean a lot to him, and your son may enjoy it, too. The space can remain a "cave" yet, as it's not very visible from your main living area. How old is your son? I'd get him involved in choosing the decor. It will make a difference in how he "owns" the room and takes care of it.