My wife runs a podcasting studio. They have a small office in a larger office complex. They want to turn one of the offices into a roundtable recording studio. I am more than capable of building over the windows. What I need help with is working with the AC vent that is in the office. There is a constant hum from one skinny vent in the sealing. Do any of you have a DIY way to baffle this sound?
Hum sounds like fan noise to me, which you’re not real likely to get around.
Wind noise can be mitigated with what could be described as a large fabric tube with holes that is suspended from the ceiling and attached to the vent…
Would a heavier fabric be better for that? I have some pretty heavy felt and was thinking about using that seeing as it is pretty porous and soft.
It is mostly wind noise the fan noise seems to be mostly mitigated by the fans being pretty far off from the vent. (i.e. looks like the last one on the run)
I’ve never really looked at one up close, but seen a lot in TV studios. It might assist in absorbing some additional noise to have a thicker fabric.
Best I can advise is to increase the size of the duct & diffuser/style. That wind noise comes from the velocity of the air being high. That’s usually done because of the velocity it needed for the “throw” of the air to keep the room cool or sure cheap construction. By throw, I mean to get from one side of the room to the other or wipe the windows to keep the envelope cool that way.
Interesting this may be a curious way to solve this problem too.
Or you can do it the way they handled it at SMU. Turn off the AC and record only while sweating through your shirt in the booth.
Or use a Ductless A/C unit for the room. Extremely low noise. Very efficient. It isn’t the lowest budget option, but it would save you having to work around the usual issues. I have seen them in a couple of house of worship production studios.
unfortunately, due to the infrastructure of the office, we can’t turn this vent completely off or control the thermostat.
Where I work I have helped build a bunch of voice tracking booths for syndicated radio formats, live syndicated show studios, and jingle/production studios and suites.
You can use Auralex or similar acoustic foam panels on the walls to reduce reflections or noise coming through the walls. Adding a drop threshold to the door and tighter foam seals on the door will help with outside noise from the hall.
The HVAC noise will require modification by someone who is familiar with proper duct sizing and installation and with the special acoustic needs of recording studios. The vent and duct sizing and choice of vent and intake grills and the balance of the system were all redone to cut down on the noise in our studios. I leave the HVAC system set to always have the blower fan on so there is no whoosh when the system kicks on and to keep the sound levels fairly constant. Also with using microphones with the proper pattern and a voice processor and properly setting the compressor and limiter you can make most of the outside noise go away. We use Symetrix 528E voice processors in all voice tracking studios and they work great. You need one per microphone channel though.
If you are doing this in a space that is a commercial building you will want to be sure you use UL approved and properly rated materials so the fire marshal does not have an issue and force you to remove it. Also do not block the sprinkler heads with any material. You must keep several feet clearance around them or the fire marshal will write you up during inspection.
Take a look at the items under “Sound Treatment” at Broadcasters General Store. We order a large amount of stuff from BGS for use in our studios. http://bgs.cc/catalog/index.php
We converted a bunch of rooms that were built as regular offices without the normal framing, insulating, ceiling and door treatments into ten radio format voice tracking rooms. We removed the standard ceiling grid tile and replaced it with acoustic studio grid tiles that are a fairly dense fiberglass 2" thick panel with a sound transparent white coating facing into the room. This cut down on HVAC noise from the two units above some of the studios. It is not cheap at about $60 per 2x4 tile.
About a year ago we also removed several hundred square feet of the original Auralex StudioFoam wedge 2x2 acoustic foam tiles in those rooms and replaced them with a custom full wall cover stretched fabric over 2-1/2 inch thick fiberglass acoustic panels. Not cheap but very effective at controlling noise between the rooms.
If you only need room for 1-2 people they do make and sell a isolation booth pod kit that you can assemble inside an existing room. I do not remember who makes them and I know they are not cheap but for some uses they are appropriate.
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Man, this is a lot of help I am just pricing it out. I have done a lot of construction work so my Wife has me working on this. BGS looks out-standing I just need to see what their budget is so we can make some decisions this is a lot of help.
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If you are building new walls you can use rock wool type insulation in the walls and there there is special acoustic sheetrock. Our studio walls that were purpose built instead of being repurposed rooms were built with double metal framed walls with staggered studs and a 1/2 inch gap between the walls. This reduces the noise transmission between rooms. Many of our studios have 2-3 layers of acoustic sheetrock with staggered seams and green glue between the layers to create to create some very dead quiet rooms.
My office at work used to be a production editing studio and has a double sheetrock ceiling even. I have run power tools in my IT/engineering office before with the door closed and people 20 feet down the hall did not notice. Having nearly 2 inches total of sheetrock between myself and the hallway does cut down on wifi and cell phone reception if the door is closed but it blocks out much of the building noise.
You may be interested in checking out green glue. It can be used between layers of drywall and helps reduce sound transmission by dampening vibrations. http://www.greengluecompany.com/
Some other ideas that might help:
- directional and/or noise cancelling mics
- post production: analyze hum/noise and use notch filters or noise reduction.
Best to eliminate/reduce the source.
There is no substitute for a good original.
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I do my occasional sound recording in a small closet full of clothes and a rack full of ties on the door which muffles the echoes.
Check out this easily constructed Sound Cancelling Portable Box for something that might improve your sound without too much cost.
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