Noise-reducing window panels

[Chipotle]

I have plenty of acoustic panels *inside* the room where I record. The issue that is starting to annoy me more and more is the leakage from outside. I live on a busy-ish street with a main drag a block away, and the room has two big (about 2'x4') windows facing the street and another smaller one as well in the adjacent wall.

It's infuriating to be in the middle of a take and have someone drive by in a junker with no muffler. I already try to record at the quietest times possible, but a random Harley can go by at any moment, and the general rumble is always there and a high-pass filter can only do so much. The windows are old single pane double-hung (92-year-old house, historic landmark and can't replace) with glass storms on the outside.

There are companies that make clear acrylic inserts ($$), you can DIY those, or at the other extreme I've seen DIY videos for more like a wooden box (or even cement-board box) stuffed with acoustic insulation and 4" thick plugged into the frame.

I realize I'm not going to get perfect soundproofing, but even a little reduction would be nice. Anyone use some kind of window inserts or other method for reducing outside noise that comes through the window? Suggestions appreciated.

[Chipotle]

I should add a couple more details: Light can be blocked and windows don't need to be opened, at least in the two front windows. And the solution has to be removable and have as little impact as possible on the window casing (historic house thing again; I don't want to screw plywood over the whole thing, lol).

[Bob Womack]

That's a tough one because of the sounds, the construction, and the remedy. The sound you are describing, a Harley Motorcycle, is low frequency and loud. Living on a boulevard, I know it well. A Harley just went by outisde. Another problem is construction. A ninety-two year old house wasn't built to prevent transmission of that sort of sound. The walls are going to be too diaphragmatic, transmitting that sound through. It isn't just the window, it is the whole wall transmitting the sound. Even to make a difference with the window, one of the biggest factors needed is rigidity. To prevent transmission, a structure needs to be rigid, to not flex. A rigid structure will be heavy. It must be mounted rigidly without leaks. That goes against your mounting dictum. The acrylic inserts aren't rigid. Our building at work has them in office spaces and they are essentially acoustically transparent.

I know it is discouraging news, but there's a reason why studios are expensive to build: isolation from the outside is usually massive. The studio where I work has five disconnected walls, each made of three layers of sheet rock glued and screwed together, and three dead spaces between the rest of the building. We've got nearly $150,000 in architectural work to gain isolation from the rest of the building. There's a reason why studios usually don't have windows: windows are a "short" point, physically shorting out the structure from inside to outside. You can only overcome them by rigidity and dead space. Our window between the control room and studio is made up of three acoustic glass panels that are one-half inch thick each, that are mounted to three disconnected walls and are angled to prevent standing waves in the casement. All that is designed to prevent transmission of the very sounds, low frequency, that you are trying to contain.

Bob

[Chipotle]

Yeah, I know it's not an easy problem to solve, and that the low-frequency stuff is even harder to deal with. But I feel like even a small reduction would reduce my aggravation and the windows have to be leakier than the wall.

Maybe I'll just get some 1/2" plywood (or cement board?), line it with foam weatherstripping and slap it over the window interior, just to see if it helps at all.

[keith.rogers]

I've read that an airspace created with a second pane of plexiglass/acrylic (sealed well) is effective. I have not done it, but have seriously thought about it because of the random injections of lawn equipment and small airplanes (nearby, small air field). Stuff like loud motorcycle pipes are just part of the home recorder's life you have to deal with. Quick retakes and punch-ins become easier with practice .

It [2nd window pane] likely won't help much with the LF noises, because they come through *everything*. I even read that windows are actually good bass "traps" because they let the bass *out* of your studio. However, there's an obvious problem with that...

You can make a pretty good dent in external noises by really sealing all of the doors and even windows if they aren't tight. However, ventilation becomes a problem pretty quickly with that, as well. Just sealing the entry door into my small room makes a very audible difference, because while you may hear the noise coming through the window, your microphone(s) hear it coming through every single gap, and if it's coming in through one window, it's coming in through all of them.

[Chipotle]

Originally Posted by keith.rogers

You can make a pretty good dent in external noises by really sealing all of the doors and even windows if they aren't tight. However, ventilation becomes a problem pretty quickly with that, as well. Just sealing the entry door into my small room makes a very audible difference

I am fortunate in a couple other ways: radiant heat, so no whooshing air to worry about, and I can close a several doorways (room door, hallway door, other room door) to greatly reduce the noise leakage from the interior of the house. It's the exterior walls & windows that are the issue.

And like you said, you can't account for the Harleys except by punching in. It's more the low-level stuff, e.g. as the last chord is fading, a car goes by--not even a loud one, but audible tire and engine noise. If I could just reduce that by a few dB, I think I'd be happier.

I've seen those acrylic panels, and was hoping someone had real-world experience with those or other remedies. You can DIY those as well, but plywood is cheaper.

[Rudy4]

Originally Posted by Chipotle

I am fortunate in a couple other ways: radiant heat, so no whooshing air to worry about, and I can close a several doorways (room door, hallway door, other room door) to greatly reduce the noise leakage from the interior of the house. It's the exterior walls & windows that are the issue.

And like you said, you can't account for the Harleys except by punching in. It's more the low-level stuff, e.g. as the last chord is fading, a car goes by--not even a loud one, but audible tire and engine noise. If I could just reduce that by a few dB, I think I'd be happier.

I've seen those acrylic panels, and was hoping someone had real-world experience with those or other remedies. You can DIY those as well, but plywood is cheaper.

The November 2022 issue of Tape Op has an interview with Suzy Shinn, a small studio owner. When she built her studio within an old house with floor to cieling windows she wanted to keep the natural light and decrease the noise substantially. The article relates that she installed 3/4" plexiglass over the windows and it's totally usable now.

[KevWind]

In general One main key point to sound "Proofing" is (as some have noted),, a dead air space between some some kind of damping layers. What many pro studio's use for sound proofing is a wall within a wall concept specifically to take advantage of a dead air space So weather that is a plexi- glass layer that is some distance from the glass OR another option (depending on how many acoustic panels you have ) would be to make some stands for some of them and stand them close to the window blocking off the window ..

But note given it is an older house no doubt a fair amount of the Harley" sound is coming through the walls as well as the windows.... Me I would think about DYI enough acoustic panels to basically create wall with a wall effect on the street side of that room

[Rudy4]

Originally Posted by Chipotle

I have plenty of acoustic panels *inside* the room where I record. The issue that is starting to annoy me more and more is the leakage from outside. I live on a busy-ish street with a main drag a block away, and the room has two big (about 2'x4') windows facing the street and another smaller one as well in the adjacent wall.

It's infuriating to be in the middle of a take and have someone drive by in a junker with no muffler. I already try to record at the quietest times possible, but a random Harley can go by at any moment, and the general rumble is always there and a high-pass filter can only do so much. The windows are old single pane double-hung (92-year-old house, historic landmark and can't replace) with glass storms on the outside.

There are companies that make clear acrylic inserts ($$), you can DIY those, or at the other extreme I've seen DIY videos for more like a wooden box (or even cement-board box) stuffed with acoustic insulation and 4" thick plugged into the frame.

I realize I'm not going to get perfect soundproofing, but even a little reduction would be nice. Anyone use some kind of window inserts or other method for reducing outside noise that comes through the window? Suggestions appreciated.

Doug Young has posted several times in the past about his converted garage studio, essentially converting it to a "room within a room" to isolate sound from either the inside to the outside or outside to inside.

I've seen examples of folks who have this problem and purchase one of the large free standing isolation cubicles to eliminate extraneous noise when recording.

[Doug Young]

Originally Posted by Rudy4

Doug Young has posted several times in the past about his converted garage studio, essentially converting it to a "room within a room" to isolate sound from either the inside to the outside or outside to inside.

I've seen examples of folks who have this problem and purchase one of the large free standing isolation cubicles to eliminate extraneous noise when recording.

Yeah, I have a "room in a room", doubly insulated. The original purpose was to keep sound in - my son's Marshall stacks - so the neighbors would continue to allow us to live here. Now that it's my space, the isolation is helpful the other direction, but still, even with no windows, etc, if there's a loud car, gardeners with leaf blowers, airplanes overhead, etc, it's still loud enough to wreck solo acoustic guitar recording. Those kinds of sounds tend to come thru just about anything as far as I can tell.

[phcorrigan]

One relatively inexpensive thing you could try is a panel of acoustic insulation sound board that covers the window frame. This should not only reduce most sound by itself, but will provide an air gap between it and the glass.

This is the material I'm talking about: https://www.homedepot.com/p/1-2-in-x...85US/207168829

[Chipotle]

Originally Posted by phcorrigan

One relatively inexpensive thing you could try is a panel of acoustic insulation sound board that covers the window frame. This should not only reduce most sound by itself, but will provide an air gap between it and the glass.

This is the material I'm talking about: https://www.homedepot.com/p/1-2-in-x...85US/207168829

Interesting. If I just make a cover panel that covers the window frame, I'm trying to decide what material to use. Plywood has almost half the density of cast acrylic, but is far cheaper so you could easily use double the thickness. Cement board is denser yet. I can't find the density of that sound board.

So, a question for the engineers---is density the key, or just overall mass? Is a thinner but more dense material better, or is a thicker but less dense material the same as long as the overall mass is equal?

I also have this weird idea for a "two-sided" window panel. A heavy panel that seals against the window on the exterior side, and on the interior it has a 2" or 4" frame to enclose OC703 or Rockwool acoustic material for sound dampening the interior of the room.

[Bob Womack]

Originally Posted by Chipotle

Interesting. If I just make a cover panel that covers the window frame, I'm trying to decide what material to use. Plywood has almost half the density of cast acrylic, but is far cheaper so you could easily use double the thickness. Cement board is denser yet. I can't find the density of that sound board.

So, a question for the engineers---is density the key, or just overall mass? Is a thinner but more dense material better, or is a thicker but less dense material the same as long as the overall mass is equal?

I also have this weird idea for a "two-sided" window panel. A heavy panel that seals against the window on the exterior side, and on the interior it has a 2" or 4" frame to enclose OC703 or Rockwool acoustic material for sound dampening the interior of the room.

It is rigidity. That is why each of the inner shells (three shells per room, five shells between me and the rest of the building) consists of three sheets of sheetrock, glued and screwed to individually framed walls with their seams overlapped. The goal is to prevent the barrier from being tympanic, ie. flexing and vibrating under sound pressure from without and transmitting that sound within.

Bob

[Chipotle]

Originally Posted by Bob Womack

It is rigidity. The goal is to prevent the barrier from being tympanic, ie. flexing and vibrating under sound pressure from without and transmitting that sound within.

That makes sense. Wood certainly vibrates (we make guitars with it!), even something thick. I can see heavy acrylic maybe flexing less. Sheetrock or cement board being maybe the stiffest? I'm not sure a "tap test" is the best way to determine lack of flex, but I'm imagining hitting a wooden panel with a mallet and the resulting sound, then a piece of acrylic, then a sheet of drywall, then cement board.

In the end, it'll only make a small overall difference anyway, since other factors will probably swamp the material contribution. But maybe time to experiment!

[Chipotle]

Update: I got an estimate from the acrylic window insert company. Just over $1000 for just three windows, not particularly large (two 27"x53" and one 27"x33").

To experiment, I made sealed plywood covers for the two front windows. I pulled out a couple sheets of 5/8" plywood I had around, cut it to a little bigger than the interior inner window dimensions, and bought some "Auto & Marine Rubber Weatherseal", which was an adhesive neoprene rubber half-round "tube" of about 3/8". I put the weather seal on the back and bottom of the plywood sheets, pressed them up against the window frame to compress, and held it them place with a few storm window clips. Cost for the rubber seal, clips and screws, about $65.

The result: using a phone sound meter app, the base noise level in the room without significant outside noise was 32dB. Before the panels were in place, softer "whooshing" cars were in the 40-45dB range, and louder ones well over 50dB. Afterwards, the softer cars measured 35-39dB, and louder ones were in the mid-40s and up.

No, it wasn't a panacea, of course. The Harleys are still going to ruin a take. But it seems to be a 6dB-ish general level reduction, and the whooshing midrange road noise that was most prevalent seems to be reduced even more. It's enough to push the noise floor down audibly, and some vehicles that might have been noticeable on a take may not be a problem any more.

Downside, of course, is that the windows are completely blocked from opening and no light comes in. I did have to drill a few screw holes in the window frame, but those could be patched easily.

Not sure if I'll put plywood over the remaining, smaller window that doesn't face the street. I may still buy one of the plexiglass inserts ($240) since I do want some light and the ability to open a window if needed.

But at least for my purposes, the experiment was a success--far less money, and probably better sound blockage than 1/4" acrylic. I'm a happier camper when I put on the headphones now.