quieting a furnace/blower/recording studio
December 29, 2018 1:43 PM Subscribe
Is there any way to bring down the noise of a furnace/blower in a closet that shares a wall with my home recording studio?
I do recordings from home for my work. I have a decent set up with a fairly high end pre built modular vocal booth. The booth knocks out a good amount of noise. Unfortunately the room the booth/office is in shares a wall with the furnace/blower closet. I recently got a new furnace which I was told would be noticeably quieter then my 30 plus year old furnace. Nope. I don't think it's any quieter. Right outside the furnace with the closet closed I get about 54db of noise. Inside my office with the door closed it goes down to about 38db. Inside the booth it goes down to about 24db. While you may be thinking 24db is plenty quiet I can still audibly hear a little bit of a low rumble from the blower. If I'm doing a recording where I need to bring up the volume a lot in post that sound is audible enough where it needs to be dealt with. And while it's not hard to get rid of it with a de noiser I really want to bring the noise down by about 4db which should basically make it inaudible inside the booth. So my question is do you have any recommendations as to how to do this? Maybe wrap the furnace with a vinyl loaded sound blanket? Other ideas? Any thoughts here are appreciated!
I do recordings from home for my work. I have a decent set up with a fairly high end pre built modular vocal booth. The booth knocks out a good amount of noise. Unfortunately the room the booth/office is in shares a wall with the furnace/blower closet. I recently got a new furnace which I was told would be noticeably quieter then my 30 plus year old furnace. Nope. I don't think it's any quieter. Right outside the furnace with the closet closed I get about 54db of noise. Inside my office with the door closed it goes down to about 38db. Inside the booth it goes down to about 24db. While you may be thinking 24db is plenty quiet I can still audibly hear a little bit of a low rumble from the blower. If I'm doing a recording where I need to bring up the volume a lot in post that sound is audible enough where it needs to be dealt with. And while it's not hard to get rid of it with a de noiser I really want to bring the noise down by about 4db which should basically make it inaudible inside the booth. So my question is do you have any recommendations as to how to do this? Maybe wrap the furnace with a vinyl loaded sound blanket? Other ideas? Any thoughts here are appreciated!
Response by poster: Thanks for the reply rhizome. I believe the sound is being transmitted through the walls. Interesting video with the double rock wall.
posted by ljs30 at 2:24 PM on December 29, 2018
posted by ljs30 at 2:24 PM on December 29, 2018
You sort of touched on this problem before when asking about the booth.
It comes back to the same thing - blocking or diffusing high frequencies is easy, but low frequencies are inherently much harder. At the volumes you're talking about, the decibel measurement is probably less important than the frequency.
Have you already tried high-passing everything? Rumble isn't generally musical, and unless you're recording a five string bass or kick drum down there, there's nothing useful happening under about 100Hz. Really without nice-sounding room (or even with one most of the time) I'd be DI'ing the bass and using a sample or close-miking the kick anyway. In an isolated booth there's not a lot of reason not to close-mic everything at fairly low levels, because the room is theoretically supposed to be dead so there's no point in recording it.
About half of my mics have some sort of low cut/high pass switch, and failing that it's pretty trivial to patch one in on your DAW or buy a channel strip that has one. I'd definitely play with this a little. Also if you're using e.g. a big sensitive large-diaphragm cardioid condenser you may want to consider borrowing a decent large-diaphragm dynamic in the Shure 7b / EV Re20 family, or a figure 8-pattern ribbon/condenser with the null pointed at the offending wall.
Absorbing big bass waves still and always means a big thick pile of something and/or the decoupling suggestions mentioned above. Big studios spend tens of thousands of dollars on whisper-quiet HVAC units, but I really suspect you can get rid of most of this in other ways.
posted by aspersioncast at 4:53 PM on December 29, 2018
It comes back to the same thing - blocking or diffusing high frequencies is easy, but low frequencies are inherently much harder. At the volumes you're talking about, the decibel measurement is probably less important than the frequency.
Have you already tried high-passing everything? Rumble isn't generally musical, and unless you're recording a five string bass or kick drum down there, there's nothing useful happening under about 100Hz. Really without nice-sounding room (or even with one most of the time) I'd be DI'ing the bass and using a sample or close-miking the kick anyway. In an isolated booth there's not a lot of reason not to close-mic everything at fairly low levels, because the room is theoretically supposed to be dead so there's no point in recording it.
About half of my mics have some sort of low cut/high pass switch, and failing that it's pretty trivial to patch one in on your DAW or buy a channel strip that has one. I'd definitely play with this a little. Also if you're using e.g. a big sensitive large-diaphragm cardioid condenser you may want to consider borrowing a decent large-diaphragm dynamic in the Shure 7b / EV Re20 family, or a figure 8-pattern ribbon/condenser with the null pointed at the offending wall.
Absorbing big bass waves still and always means a big thick pile of something and/or the decoupling suggestions mentioned above. Big studios spend tens of thousands of dollars on whisper-quiet HVAC units, but I really suspect you can get rid of most of this in other ways.
posted by aspersioncast at 4:53 PM on December 29, 2018
A switch to disable the furnace or dampen and or baffle the ductwork to control the reverberations inside .
posted by hortense at 6:38 PM on December 29, 2018
posted by hortense at 6:38 PM on December 29, 2018
Simplest thing? Turn the thermostat way down when you're recording so that the furnace doesn't kick on. Or just get a switch installed and turn it right off when you don't want it to interfere.
If you want it to be able to run, it's gonna be tougher. Not impossible though, because you have multiple angles of attack you can pursue. First, have the furnace remounted on some rubber standoffs or a thick rubber mat so that its vibrations don't get into the floor so much. Second, do the same for the recording booth. Third, build a false wall between the recording booth and the furnace room—also mechanically isolated from your building's frame, so just wedged in place with rubber matting serving as the shims—out of 2x6 stock, insulate it with Roxul mineral wool, and sheetrock it with 5/8" drywall on both sides. That'll probably do the trick.
posted by Anticipation Of A New Lover's Arrival, The at 7:02 PM on December 29, 2018
If you want it to be able to run, it's gonna be tougher. Not impossible though, because you have multiple angles of attack you can pursue. First, have the furnace remounted on some rubber standoffs or a thick rubber mat so that its vibrations don't get into the floor so much. Second, do the same for the recording booth. Third, build a false wall between the recording booth and the furnace room—also mechanically isolated from your building's frame, so just wedged in place with rubber matting serving as the shims—out of 2x6 stock, insulate it with Roxul mineral wool, and sheetrock it with 5/8" drywall on both sides. That'll probably do the trick.
posted by Anticipation Of A New Lover's Arrival, The at 7:02 PM on December 29, 2018
Yup, just make sure it won't kick on while you're working. I have to do the same in the summertime with my A/C.
posted by tomboko at 2:10 AM on December 30, 2018
posted by tomboko at 2:10 AM on December 30, 2018
And yeah, I can't believe I didn't suggest just turning the HVAC off while recording. This is by far the easiest solution and the one I generally take when tracking acoustic instruments or vocals, although I still low-pass most things in case a freight train rolls through.
posted by aspersioncast at 10:43 AM on December 30, 2018
posted by aspersioncast at 10:43 AM on December 30, 2018
Response by poster: Turning off the AC is of course the easiest solution. And that's what I've done for several years during the summer. Thing is I live in the valley of los angeles where we can have week long heat waves of 110 degrees. At that temperature turning off the AC is pretty brutal. When you turn off the AC in that weather you can see the temperature rise pretty quickly in an hour or two and sometimes I have sessions that take that long. So when you turn the AC back on it's very hard to cool the house back down. This is my main reason for wanted to have the ability to leave it on. Though in reality most of the time it's fine to just turn it off.
I know that high end studios spend tons of money dealing with this issue. I guess I'm more so disappointed that both my new booth and new furnace didn't solve the problem. Certainly not anyone's fault on here...and I greatly appreciate everybody's advice for sure!
posted by ljs30 at 3:16 PM on December 30, 2018
I know that high end studios spend tons of money dealing with this issue. I guess I'm more so disappointed that both my new booth and new furnace didn't solve the problem. Certainly not anyone's fault on here...and I greatly appreciate everybody's advice for sure!
posted by ljs30 at 3:16 PM on December 30, 2018
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The best thing would be to construct a decoupled booth, a room within a room. The cheaper-but-less-easy would be to change the mounting of the furnace to decouple that. The cheapest and possibly fastest would be to double-rock the wall between, optionally using resilient channel. [insert your own religious war here] How's the insulation?
posted by rhizome at 2:05 PM on December 29, 2018