I am interested in understanding the key factors in sound proofing a window.

I once stayed in an old hotel (built about 1815) in New York City on Canal Street and the room was absolutely silent which may be hard to believe for anyone who has been to Canal Street, but it was actually perfectly silent.

The reason for this was that the windows were doubled (not double pane); ie there were two layers of windows. The outer window was some kind of tempered glass and was sized exactly to the outer frame of the window and had been caulked into place. The inner windows were the original casement windows from the 19th century. Due to the thick width of the window frame there was a separation of perhaps 10 inches between the air tight window on the outside and the inner window.

I have been in houses with normal modern double paned windows and they are definitely not sound proof, so I am wondering what was special about the arrangement in the hotel. My guesses are:

(1) The outer window was absolutely airtight, but modern windows are not perfectly air tight but have joints and so forth that let sound past, and that made the difference.

(2) The distance between the panes was 10 inches and for some reason that is far more effective than two panes that are close together.

Does anybody know if either of these two factors (or another) is what is critical in making a window sound proof?

  • What floor were you on in this NY hotel? Commented Apr 6, 2018 at 14:53
  • Have you contacted the hotel to ask if there was anything special about the windows other then what you observed? How thick was the outer pane of glass?
    – Alaska Man
    Commented Apr 6, 2018 at 15:53
  • There are acoustic laminates that can be applied to glass to cut sound. I've been to a modern hotel that is under an international airport flight path and you don't hear the planes. Commented Jan 19, 2020 at 1:08
  • Plate glass makes an excellent window, a single layer is much thicker than normal window glass, at the cost of being heavier. Two of them in "series" would make a most efficient "double-glazed" window.
    – Criggie
    Commented Oct 15, 2020 at 4:47

2 Answers 2


Factors affecting the quality of soundproofing windows are: 1) thickness and type of glass, 2) depth of air space, and 3) construction of frame, and 4) slope of glass.

1) Some glass conducts more sound than other types. In addition, using different thicknesses of glass will help stop certain wave lengths of sound than other thicknesses, so you need to vary the thicknesses.

2) Various depth of air gap can help stop various wave lengths too.

3) Solid (or insulated) window frames is better than hollow frames.

4) Installing one of the frames sloping to the other frame will help also. If you look close, you’ll see that the frames are not parallel.

Think of sound booths. Here’s an article that helps explain:



Key factors are mass and air gap. Sounds like this hotel had both.

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