Question about eliminating room echo.

[harmonica44]

I am about to shoot my first real short soon, and could use some advice. I had a sound guy but he dropped out for personal reasons cause of a family crisis, he had to go back home for. I keep reading that you have to use blankets or some sort of covers to mask the echo, when using a shotgun mic indoors. But the question is how much blanket? Like say the person holding the boom, is pointing the mic above the actor, pointing almost straight down towards the actors mouth. This means it will be pointed almost straight down to the floor. So since the shotgun is very directional, it will pick up the noises from the floor, a lot more than anywhere else, as I understand it.

Does this mean that I have to cover the whole floor, or just a certain amount, around the pick up direction of the mic? Or what do I have to do exactly? I've been practicing but still haven't quite got the hang of it. Thanks.

 

[harmonica44]

Sure I'll try to figure it out and take the advice given. Thanks.

 

[gorillaonabike]

ROFL LMAO - My sides hurt...

I didn't believe it was possible to breathe tea out through my nose but I've just achieved this.

However, wait until Harmonica44 creates the best d@mn short ever seen on IndieForum and his questions change from 'which way around do I hold a camera' to 'how do I spend my latest $10m USD in funding...?'

 

[Synia]

However, wait until Harmonica44 creates the best d@mn short ever seen on IndieForum and his questions change from 'which way around do I hold a camera' to 'how do I spend my latest $10m USD in funding...?'

Noone said he can't make it that far. I'm just saying he can't do that in his first film.

And personally, i think Harmonica44 is kinda like a community project of this forum, lol

@OP We'll all be very proud of you when you get to make your millions of dollar!!!! ... But for now.... GO AND MAKE YOUR FIRST FILM ALREADY!!!!

EDIT: Correction: SHORT FILM

 

[WalterB]

Maybe Harmonica doesn't know that 'talent' means actor or actress, so he thinks he did a discovery about the relation between distance to the source and amount of reverb.

Yes,there is a relation between distance to the soundsource and the amount of recorded reverb (or echo).
First: the closer the mic gets to the source: the louder the source gets recorded.
(Very logical)

Second: reverb (or echo) is 'everywhere' in the room, since it has no real point of origin. It bounces from all the surfaces. This roughly* means the reverb has (approx.) the same loudness wherever you point the microphone.

Combining these two 'facts' mean that the closer the mic is to the source the louder the source sounds in relation to the reverb.

Let's put some (unrealistic) numbers to it:
the reverb is 30 dB.
from 6 feet the source is 35 dB.
This means the difference is only 5 dB: the reverb is very noticable.

move the mic to 3 feet: the source is 45 dB
This means the difference is 15 dB: the reverb is relatively less noticable.



*)
This is not true near dampening surfaces or in corners and some architecture can create big differences


BTW, we should not forget that Harmonica tries to shoot his first short by shortcutting through a few years of filmschool on this forum.

 

[GuerrillaAngel]

we should not forget that Harmonica tries to shoot his first short by shortcutting through a few years of filmschool on this forum.

On the other hand, had he gone to film school there's a risk he may never make his own film having "learned" that you need a sizable crew and a crane to "properly" make a film.

Too bad he lives out in the boondocks, he'd be a positive asset as a PA to someone's film project.

 

[harmonica44]

Maybe Harmonica doesn't know that 'talent' means actor or actress, so he thinks he did a discovery about the relation between distance to the source and amount of reverb.

Yes,there is a relation between distance to the soundsource and the amount of recorded reverb (or echo).
First: the closer the mic gets to the source: the louder the source gets recorded.
(Very logical)

Second: reverb (or echo) is 'everywhere' in the room, since it has no real point of origin. It bounces from all the surfaces. This roughly* means the reverb has (approx.) the same loudness wherever you point the microphone.

Combining these two 'facts' mean that the closer the mic is to the source the louder the source sounds in relation to the reverb.

Let's put some (unrealistic) numbers to it:
the reverb is 30 dB.
from 6 feet the source is 35 dB.
This means the difference is only 5 dB: the reverb is very noticable.

move the mic to 3 feet: the source is 45 dB
This means the difference is 15 dB: the reverb is relatively less noticable.



*)
This is not true near dampening surfaces or in corners and some architecture can create big differences


BTW, we should not forget that Harmonica tries to shoot his first short by shortcutting through a few years of filmschool on this forum.

Yes I would have gone to film school if I could have afforded it. Well in my experience, the closer I put the mic, the less echo there seems to be, and this is also if I have the dials on certain settings of course. I wasn't able to get a cardioid mic before cause the one I wanted, no stores, had and my sound guy (who now is out), was very good with a shotgun, and hadn't had much experience with cardioids. But my friend has a cardioid and has offered to let me use it. I could since Alcove said it was better with indoors. But I have had no practice using one indoors yet. Do I put the blankets all around the same way with a cardioid and what not?

 

[WalterB]

..........Well in my experience, the closer I put the mic, the less echo there seems to be, ......

This is what Alcove Audio already told you before you mentioned it and I just explained (or tried to explain) a bit of the physics why this is the case.

Sometimes I get the feeling you don't read (English) very well.

 

[harmonica44]

Oh ya, sorry I read Alcove's explanation wrong. I haven't slept well the past couple of weeks, and it's mostly cause of pre-production and the auditions. Which is why I am not at my most functional. Things are coming around now though. I will try to get the mic in as close as I can, and tonight I managed to record dialogue in a non-blanketed room with no echo! Or at least not much noticeable echo. I was practicing at a location I will be using, but the owner will not allow blankets stuffed everywhere so I wanted to get practice for that.

 

[Wombat]

Great thread. Added to 200+ page bookmarks re: filmmaking. Thanks, guys.

This is kind of an oddball question, but would blankets mitigate echo better if they weren't directly against a wall? Say I had adjustable PVC frames that I could throw my blankets (actually massive, ridiculously thick comforters for Florida) and place them a few inches from the wall (effectively covering the same surface area a pinned blanket would). Would that work better than, say, thumbtacking the same doubled-up blanket to the wall?

I only ask because I know that air is an excellent insulation 'material' for construction and am pig-ignorant about acoustics.

 

[Alcove Audio]

would blankets mitigate echo better if they weren't directly against a wall?

Yes. Mitigating bounce is half of the battle. You hang your blankets so there a lots of folds. If you can get 6" from the wall all the better. The sound is partially absorbed, what's left goes through the blankets, bounces off of the wall and some of what is left is absorbed on the way back.

 

[Wombat]

Yes. Mitigating bounce is half of the battle. You hang your blankets so there a lots of folds. If you can get 6" from the wall all the better. The sound is partially absorbed, what's left goes through the blankets, bounces off of the wall and some of what is left is absorbed on the way back.

That's kind of what I imagined happening in my head, but like I said, pig-ignorant, etc. Thanks.

I'm guessing making 'lumps' like in egg crate foam is a superior option to simply folding it, though that might be difficult to arrange on a stand.

 

[Alcove Audio]

Egg cartons do nothing to absorb sound; at best they very minimally bounce the sounds in different directions. Just because it looks like true sound treatment doesn't mean that works the same way.

If you really want the egg carton thing to work you have to fill all of the egg slots with something that will actually absorb sound.

 

[Wombat]

Egg cartons do nothing to absorb sound; at best they very minimally bounce the sounds in different directions. Just because it looks like true sound treatment doesn't mean that works the same way.

If you really want the egg carton thing to work you have to fill all of the egg slots with something that will actually absorb sound.

Sorry, I was just trying to make a visual for the how the blankets would look; I'm well aware that egg crate foam doesn't do too much to dampen sound since my old roommate was a drummer.

What I meant to convey was that I would be lumping the blankets up to have peaks and valleys and creases and folds rather than simply letting them hang flat and folded.

EDIT: The idea being that there would likely be more surface area for it to bounce off of in a direction away from the mic, but I guess your point is that it's the material and not the shape that matters.

 

[Alcove Audio]

Shape matters as well. For the most part it's avoiding parallels. Parallels create standing waves. So it's better to have the blankets 6" from the wall at one end and three feet from the wall at the other.

If you have an eight foot long blanket it should only occupy four feet of space - it will have lots of folds in it like curtain.

 

[harmonica44]

Okay that's good to know. Thanks. One of the person's I'm using a location from is pretty touchy and will not allow blankets to be kept on the walls. There are paintings and stuff on the walls, and he doesn't want them touched. The floor is okay though. It seems I can eliminate the echo if I adjust the levels a certain way, and don't need blanket on the walls, as long as the floor is covered, but I hope that's not just my ear telling me that through the headphones, and that I'm hearing it right.

 

[Alcove Audio]

You use C-stands and rods to hang the blankets.

 

[harmonica44]

Oh C stands. Thanks. I'll see if I can get some. If not I'll use coat hangers or something.

 

[gpforet]

That would have to be a very sturdy coat hanger. My sound blankets weigh about 3-4 lbs each. I use microphone stands with booms. I configure the boom like a T, and extend the stand to full height (which is around 6-1/2 feet). I clamp the blankets to the boom with gator clamps. Right now I carry 15 blankets and stands.

Oh C stands. Thanks. I'll see if I can get some. If not I'll use coat hangers or something.

 

[harmonica44]

I'll have to think of something. I don't have T stands or mic stands as of now and like most movie making things, mic stands have to be ordered, where I live. I'll see about the C stands. Thanks.