As you audio guys know, the sound for my web series is abysmal. The production reality that I have to live with is that I am shooting in an actual concrete and steel bunker. I also do not own the property so cannot drill into the walls. The space that I use is 13'4"X17'2"X9'. What can I do to help the sound that does not attach to the walls or ceiling, won't interfere with camera and light placement too badly, and does not cost a truck load of cash?
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Inexpensive Sound Treatment
- Thread starter Lucky Hardwood
- Start date
I would have to find someplace to shoot the greenscreen that is better for sound. I do not currently have such a location. I was thinking about getting some cushion foam and rolling it into tubes to place around the space. I am hoping to get some real world input before I go to the fabric store and drop money on the foam.
There is foam and then there is foam! Foam falls into two main categories, open cell foam and closed cell foam. Closed cell foam is cheap and is the type of foam you are most likely to come across but is next to useless when it comes to sound absorption! Acoustical foam isn't just weird shaped foam, it is always one sub-type or another of open cell foam. In other words, placing tubes of standard (closed cell) cushion foam around the space will probably diffuse the sound reflections, which may or may not help to a limited extent but what you really need is sound absorption rather than sound diffusion.
An effective and fairly cheap way of achieving sound absorption would be to make some wooden frames, fill the frames with mineral wool (cheap fibreglass is OK, stone or rock wool is better) and then cover the whole thing with material to stop the dust escaping, you can get cheap upholstering material designed for this purpose. A less effective but even cheaper and more portable alternative would be to get old blankets, curtains or rugs (the thicker the better) and hang them on stands around the walls. 3 basics to remember:
1. The more surface area of the concrete you can cover the better the results.
2. Placing the absorption a little away from the wall is actually much better than placing it directly against the wall.
3. Don't forget the floor. Old rugs or carpeting, again the thicker the better, will help considerably.
G
Thank-you APE. I have an abundance of photographic backdrop stands and can use them for that purpose. I can hit the carpet supply house and get some large remnants for cheap because I don't care about the color. Where would be a good source for closed cell acoustic foam?
I take it you mean open-cell foam? Closed cell foam is not much use, acoustically speaking. With the exception of specifically designed acoustic foam panels, foam is generally avoided for acoustic applications because it's difficult to know or find out if it's open or closed cell and in the absence of specific information most generic foam is likely to be closed cell. It is sometimes possible to find great deals on acoustic foam panels on eBay or Craigslist. Consider though that most bare acoustic foam panels are designed to be mounted or glued directly on to walls so you may still need to build some sort of frame to stop it just ending up as a heap on the floor! Again, with an entirely concrete room, a few acoustic panels is only going to marginally improve the situation, you want to be covering as much of the concrete as possible. In this instance, more coverage with a lesser material will likely produce better results than lesser coverage with specific acoustic materials.
If you already have suitable stands, that would seem the cheapest way to go, presuming they are able to support the weight of the carpets. Thick, soft, fluffy carpets will absorb a wider range of frequencies than hard office type carpets which will, to some degree, reflect certain frequencies. Thick blankets (or layers of thin blankets) may prove to be more effective than harder type carpets for the range of frequencies usually associated with spoken dialogue, especially as you will be mounting them on stands a little away from the walls.
G
Is there a lav mic that is [erhaps optimal for the environmen this project is shot in?
Something that has a horrid drop-off beyond just a few inches away, and maybe not very sensitive to whatever echo frequencies are boucing around at?
Or is it reasonable to try to figure out at what frequesncy the echo is coming in at and just set the field recorder's filter to skip/attenuate that area?
Hi/low/notch/band filters?
Something that has a horrid drop-off beyond just a few inches away, and maybe not very sensitive to whatever echo frequencies are boucing around at?
Or is it reasonable to try to figure out at what frequesncy the echo is coming in at and just set the field recorder's filter to skip/attenuate that area?
Hi/low/notch/band filters?
Sounds like you need some mass in there to absorb that sound!
FWIW, I helped a friend out a little while ago in building some large acoustic absorbers for a project studio, and we were able to build them incredibly inexpensively. They're not the most portable of things, but if you're looking for a semi-permanent solution, or at least are not needing to carry them all over the place - look into it. We used glasswool insulation in ~220mm thickness IIRC. Found the plans for frames/material etc. as mentioned by APE on a sound forum I believe.
I could imagine covering absorption panels in black or white fabric and using them as cutters or reflectors!
FWIW, I helped a friend out a little while ago in building some large acoustic absorbers for a project studio, and we were able to build them incredibly inexpensively. They're not the most portable of things, but if you're looking for a semi-permanent solution, or at least are not needing to carry them all over the place - look into it. We used glasswool insulation in ~220mm thickness IIRC. Found the plans for frames/material etc. as mentioned by APE on a sound forum I believe.
I could imagine covering absorption panels in black or white fabric and using them as cutters or reflectors!
The frequency/frequencies of the sound reflections (echoes) are obviously going to be directly related to the original sound source creating the reflections and the absorption characteristics/resonant frequencies of the surfaces from which they are reflecting. Unfortunately, solid concrete is hard and dense, absorbs very little and therefore reflects almost all frequencies (except low frequencies which are not much of a concern with the human voice anyway). Therefore, in attenuating the frequencies of the reflections (of the human voice) you will also be attenuating the frequencies of the dialogue you wish to retain. Filtering is only really of any use when trying to remove frequency content caused by noise other than that produced by the human voice, say earth loop or certain other types of electrical hums in the case of notch filters and HF hiss or LF rumble in the case of hi/lo filters.
A lav would likely help to a degree, whether it would be enough on it's own (without acoustic treatment) in a small, entirely concrete surfaced room is doubtful.
G
In the past, we've used cheap, thick egg crate foam from the fabric store. With a large sheet we held it up around our actor for a makeshift "Wild ADR on location" booth. We have carpet sample squares that pack and travel nicely to put down on the floor of a deep shag type (discontinued samples from the carpet stores, they just throw them away otherwise). Tons of thickish blankets to hang around the set as well.
Low budget and not ideal, but another set of options. Having some framed standing options would be a nice addition to my kit though that I may pursue.
Low budget and not ideal, but another set of options. Having some framed standing options would be a nice addition to my kit though that I may pursue.
Set dress with big couches, or desks with big cubbys. Use things in the diagetic world to kill the sound. Sound can go die in a big shelving unit
The very first sound guideline I was taught is "2 feet is too far," so shoot tighter than you would like in order to give your boom op the chance to get closer!
And start thinking more about post audio design too, a good bed of music can help in masking slightly imperfect audio. Of course this isn't a go-ahead to ignore all the other great tips.
And listen to everything APE says, from what I've read of his on this forum is pure gold
The very first sound guideline I was taught is "2 feet is too far," so shoot tighter than you would like in order to give your boom op the chance to get closer!
And start thinking more about post audio design too, a good bed of music can help in masking slightly imperfect audio. Of course this isn't a go-ahead to ignore all the other great tips.
And listen to everything APE says, from what I've read of his on this forum is pure gold
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Okay, let's sum it all up...
As APE mentioned, all foams are not acoustic foams. But what you need is sound absorption and deflection.
Real acoustic foams are great, but the better they are the more expensive they are. Quality 2" acoustic foams like Auralex run about $5 a square foot, $3 a square foot when bought in bulk:
http://www.bhphotovideo.com/c/produ..._SINGLE_Studiofoam_Wedgies_Charcoal_Grey.html
http://www.bhphotovideo.com/c/produ...DGIE_24_Studiofoam_Wedgies_Charcoal_Grey.html
Acoustic blankets are also a terrific option - and the better ones cost as much as acoustic foam, although it's very nice to be able to fold them up and reuse them for years as needed.
http://www.bhphotovideo.com/c/product/140104-REG/Matthews_329040_1_Sound_Blanket_with_Grommets.html
http://www.filmtools.com/filmtools-furniture-pads-black.html?gclid=CO3ejfi86LsCFSRk7AodIEAAYQ
What you need is anything that will absorb sound. Moving pads, although not as good as real sound blankets, are an acceptable substitute. Bring pillows, quilts, etc.; anything that has some "soft" density. When you hang the sound blankets, moving pads, quilts, whatever from the C-stands DO NOT pull them tight; leave lots of folds. Also, DO NOT put them parallel to walls, put them at angles.
Get as much carpeting as you can - the thicker the better. Put it everywhere the actors feet will not be seen.
Part of the issue with hard surfaces like your concrete and steel bunker can be standing or stationary waves. This is common in square and rectangular rooms. A sound hits wall "A", bounces off, hits wall "B", bounces off, hits wall "A", bounces off, hits wall "B", bounces off, etc. This is like the infinite reflection effect of a mirror. This standing/stationary wave creates greatly exaggerated frequencies and exaggerated ambient/reverberant echo. The hard walls alone will create the exaggerated bathroom/gymnasium effect. Using a shotgun mic will greatly overemphasize this effect. Add in standing waves and you're in for a sound disaster.
So, put in as much sound absorbing material into the bunker as you can. Place it all at odd angles to the walls to deflect sound as much as possible. Get sound blankets, etc. as high as possible to mitigate reflections from the ceiling. Put as much carpeting down as possible. Use a hypercardioid mic rather than a shotgun and get in really, really close; use omni lavs as well if at all possible.
As APE mentioned, all foams are not acoustic foams. But what you need is sound absorption and deflection.
Real acoustic foams are great, but the better they are the more expensive they are. Quality 2" acoustic foams like Auralex run about $5 a square foot, $3 a square foot when bought in bulk:
http://www.bhphotovideo.com/c/produ..._SINGLE_Studiofoam_Wedgies_Charcoal_Grey.html
http://www.bhphotovideo.com/c/produ...DGIE_24_Studiofoam_Wedgies_Charcoal_Grey.html
Acoustic blankets are also a terrific option - and the better ones cost as much as acoustic foam, although it's very nice to be able to fold them up and reuse them for years as needed.
http://www.bhphotovideo.com/c/product/140104-REG/Matthews_329040_1_Sound_Blanket_with_Grommets.html
http://www.filmtools.com/filmtools-furniture-pads-black.html?gclid=CO3ejfi86LsCFSRk7AodIEAAYQ
What you need is anything that will absorb sound. Moving pads, although not as good as real sound blankets, are an acceptable substitute. Bring pillows, quilts, etc.; anything that has some "soft" density. When you hang the sound blankets, moving pads, quilts, whatever from the C-stands DO NOT pull them tight; leave lots of folds. Also, DO NOT put them parallel to walls, put them at angles.
Get as much carpeting as you can - the thicker the better. Put it everywhere the actors feet will not be seen.
Part of the issue with hard surfaces like your concrete and steel bunker can be standing or stationary waves. This is common in square and rectangular rooms. A sound hits wall "A", bounces off, hits wall "B", bounces off, hits wall "A", bounces off, hits wall "B", bounces off, etc. This is like the infinite reflection effect of a mirror. This standing/stationary wave creates greatly exaggerated frequencies and exaggerated ambient/reverberant echo. The hard walls alone will create the exaggerated bathroom/gymnasium effect. Using a shotgun mic will greatly overemphasize this effect. Add in standing waves and you're in for a sound disaster.
So, put in as much sound absorbing material into the bunker as you can. Place it all at odd angles to the walls to deflect sound as much as possible. Get sound blankets, etc. as high as possible to mitigate reflections from the ceiling. Put as much carpeting down as possible. Use a hypercardioid mic rather than a shotgun and get in really, really close; use omni lavs as well if at all possible.
For this series, I am a one man band as it were. I am using a Sennheiser G3 wireless lav system running into a DR100 mkII. Because of rustling noise, I clip the lav to the front of the mask. The ghillie suit hides the mic pretty well. I tried putting the mic inside the mask but it sounded like somebody blowing into it every-time I moved at all. I tried a different setup for the segment that I shot this morning and will be attempting to get the hang of Adobe Audition to edit the audio.
This certainly does help, but only to a certain extent. This combined with the other tips will give a much better result.
I shot a film a while ago. We built a set to shoot on because it was going to be easier. Plus it meant we could take walls out for certain shots, and move walls during shots so we could get the specific shots we wanted. Unfortunately, production didn't have the budget to build it on a stage, so it was built in an old warehouse.
Sound was a huge issue. After the set was built and completely dressed, it sounded a lot better than it did initially, as one might expect. But, because of the high ceiling, and the fact that I wanted to rig lights above, there was nothing on top and so the sound was still an issue.
oh, of course, my tips were small in comparison to the main points already covered, but every little bit helps! especially in such an important aspect of a movie
I'd be very careful with this! It is possible that sound can go and die in say a desk cubby or shelving unit but it's also possible that they could have the opposite effect and act like a resonating chamber, similar to the resonating chamber on an acoustic guitar. To avoid this possibility, it's often a good idea to fill a shelving unit with books or other items to absorb or diffuse the sound.
G
What sort of stands should I get?
I'm thinking something with a clamp. I tried looking for clamp stand on the internet but that wasn't very productive