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Old 05-09-2017, 05:41 AM   #1
gorillaonabike
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Low frequency sound blankets

What are the best sound blankets for low frequency noises? Traffic etc...? I know that nothing would be as good as a soundproofed room but if I need to do something on the fly near a busy road, I want to make as much of a dent in that low frequency noise as possible (in addition to all the other stuff I do).
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Old 05-09-2017, 12:14 PM   #2
joelhall
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Quote:
Originally Posted by gorillaonabike View Post
What are the best sound blankets for low frequency noises? Traffic etc...? I know that nothing would be as good as a soundproofed room but if I need to do something on the fly near a busy road, I want to make as much of a dent in that low frequency noise as possible (in addition to all the other stuff I do).
Obviously a sound proofed room what be better than anything, but this is a false analogy. You're always going to have some ambient noise in the real world. There's a few work arounds, but my first advice wouod be: microphone choice. Knowing the pick up pattern of a microphone is vital. I'd personally say it is the most important factor. Low frequency noise isn't bad per se, but the control of that noise is. The very best thing you can do to control it is use the right microphone.
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Old 05-09-2017, 12:53 PM   #3
AcousticAl
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Low frequencies are a pain in the ass because they bend and curve around corners. You can't exactly throw a gobo in their way and expect them to stop. Plus, blankets pretty much deal with everything but.

Really, dude, your first defense is the low-frequency roll-off - aka high-pass filter - either on your mic or on your mixer.

Corners of rooms are also problems because bass frequencies are basically amplified there. Auralex has portable bass traps that are stand-mounted and can be placed in corners to help tame issues, though that'd be more effective on sources from inside the room than ambient bleed from outside, but every little bit helps. And you can only place them in corners that are off-camera, so... yeah.
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Old 05-09-2017, 06:52 PM   #4
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This is the kind of thing that is handled in audio post.

Obviously, yes, you want to capture the cleanest production sound that you can. This makes the job of the dialog editor(s) and the rerecording mixer(s) A LOT easier. If none of the actors have deep voices you can roll-off the lows at about 80Hz to 100Hz. The most important aspect, however, is a properly aimed mic.

During the DX edit the DX editor will eliminate the spaces between the lines of dialog (I cut them out and drop them onto an adjoining track for just that purpose). During prep for the mix several types of noise reduction may be applied to the dialog. Room tone and/or ambient sound will replace and fill in the empty spaces between the lines of dialog, as will Foley, sound effects and music.
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Old 05-10-2017, 11:32 AM   #5
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Originally Posted by AcousticAl View Post
Low frequencies are a pain in the ass because they bend and curve around corners. You can't exactly throw a gobo in their way and expect them to stop. Plus, blankets pretty much deal with everything but.

Really, dude, your first defense is the low-frequency roll-off - aka high-pass filter - either on your mic or on your mixer.

Corners of rooms are also problems because bass frequencies are basically amplified there. Auralex has portable bass traps that are stand-mounted and can be placed in corners to help tame issues, though that'd be more effective on sources from inside the room than ambient bleed from outside, but every little bit helps. And you can only place them in corners that are off-camera, so... yeah.
Good lord those are expensive!!!

Is that just high density polyurethane foam? That stuff is expensive as a raw material, so i get it.

But I feel like I could spend $100 on a square of it, use an electric turkey carving knife and make my own bass traps in 20 minutes for 1/5 the price. Cutting the foam with a turkey knife is an old drag trick to make your own hip pads.
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Old 05-10-2017, 07:32 PM   #6
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Is that just high density polyurethane foam? That stuff is expensive as a raw material, so i get it.
No, it's not "just" high density foam; it is a specially formulated and manufactured acoustic foam. Even the shaped angles are precisely calculated for optimum bass taming. THAT'S why it's so expensive.

Using "regular" commercially available high density foam is like using actual egg cartons for sound treatment in a studio; it looks like the real deal, but only does about 5% of what the real thing does. You would do better using something like big, heavy overstuffed chairs/couches/etc.
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Old 05-11-2017, 03:28 PM   #7
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The angles can be observed and mimicked. The r&d is what makes something that like that expensive. And high density foam is already dense!

Of course I'll take your word for it. High density foam is expensive anyway so it's not like it's a "cheap" alternative
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Old 05-12-2017, 02:20 PM   #8
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The angles can be observed and mimicked. The r&d is what makes something that like that expensive. And high density foam is already dense!

Of course I'll take your word for it. High density foam is expensive anyway so it's not like it's a "cheap" alternative
But it's NOT high density foam, it's acoustic foam. There IS a difference.
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Old 06-14-2017, 06:33 PM   #9
IronFilm
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The default choice for sound blankets is to use the same blankets as the moving blankets used by moving companies.

You can get fancier ones, such as with one side white the other black (helpful so you don't interfere too much with the DoP's lighting). But fundamentally, they're basically similar to a moving blanket.

However in the end, what will make the biggest difference is picking appropriate locations.
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