This is a general idea I've been thinking about. If you framed out a new room (stand alone building in a yard) and put only very thin 1/4" ply on the walls and ceiling (inside wall 1/4" > insulation > outside wall 1/4"), in theory you'd have perfect bass response. There would be no bass reflection as it wold pass through the thin walls and insulation.
Taking that idea, what if you remove only the parts of the wall and ceiling directly in front and above the listening position?
In my situation, in front of my listening position is a huge 6' x 5' picture window and above me is an attic. If I remove the picture window in front of me and remove a similar size chunk of the sheetrock ceiling above me, replacing both with 1/4" ply, will this allow the bass to pass through and effectively eliminate nodes?
Will opening a window and part of the ceiling improve bass?
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Re: Will opening a window and part of the ceiling improve ba
Acoustic absorption is measured in units of sabins. One sabin is defined as being the equivalent of an open window with an area of one square foot. So theoretically, yes, taking out chunks of your studio walls and ceiling could, indeed, allow sound to escape.
However, it isn't really as simple as that, since there are other effects involved too. Impedance mismatch, edge diffraction, aperture size vs. wavelength, and even whatever is "beyond the window" for example, are all issues.
But the answer is no, it would not eliminate your room modes. It would reduce the intensity of the associated axial modes to a certain extent, but not eliminate them. It would have less of an effect on tangential modes, and less still on oblique modes.
Then there is the question of what is on the other side of those holes: Assuming that there is nothing at all above your ceiling except blue sky, that would have a considerable effect, but if there's a roof up there some place, then you are out of luck: all you did is to move the boundary a bit, and add an additional set of acoustic issues to your room: those associated with the attic space. The same applies to your window: provided that there is absolutely nothing beyond that window for many dozens of feet, that would be useful. But it there is anything out there, such as a wall, tree, parked car, front yard, or anything like that, then you are out of luck again.
The best way of dealing with modal issues is to just damp them with very thick absorption. It's not a perfect solution, but it works well, and it beats leaving gaping holes in your house, which might turn out to not be a god idea if you live any place where there is wind, rain, heat, cold, snow, etc. Or any place with burglars...
- Stuart -
However, it isn't really as simple as that, since there are other effects involved too. Impedance mismatch, edge diffraction, aperture size vs. wavelength, and even whatever is "beyond the window" for example, are all issues.
Wellllll... not really. It would be pretty good, but even 1/4" of ply is enough to have some effect.If you framed out a new room (stand alone building in a yard) and put only very thin 1/4" ply on the walls and ceiling (inside wall 1/4" > insulation > outside wall 1/4"), in theory you'd have perfect bass response.
Most would pass through, sure, but some would not. Some would come back again. The surface density of 1/4" plywood is around 0.75 lb/sq ft, so according to mass law that would provide about 1.5 dB of transmission loss at 100 Hz, which is really low but still not zero....there would be no bass reflection as it wold pass through the thin walls and insulation.
I think you mean "modes" not "nodes".If I remove the picture window in front of me and remove a similar size chunk of the sheetrock ceiling above me, replacing both with 1/4" ply, will this allow the bass to pass through and effectively eliminate nodes?
But the answer is no, it would not eliminate your room modes. It would reduce the intensity of the associated axial modes to a certain extent, but not eliminate them. It would have less of an effect on tangential modes, and less still on oblique modes.Then there is the question of what is on the other side of those holes: Assuming that there is nothing at all above your ceiling except blue sky, that would have a considerable effect, but if there's a roof up there some place, then you are out of luck: all you did is to move the boundary a bit, and add an additional set of acoustic issues to your room: those associated with the attic space. The same applies to your window: provided that there is absolutely nothing beyond that window for many dozens of feet, that would be useful. But it there is anything out there, such as a wall, tree, parked car, front yard, or anything like that, then you are out of luck again.
The best way of dealing with modal issues is to just damp them with very thick absorption. It's not a perfect solution, but it works well, and it beats leaving gaping holes in your house, which might turn out to not be a god idea if you live any place where there is wind, rain, heat, cold, snow, etc. Or any place with burglars...
- Stuart -