How do I reduce echo coming from large glass panes?

Question

I'm shooting a short film set in a takeout place, and our location has a large window that basically encompasses the whole front of the shop.

It also has tiled walls and floors, but seeing how our test recordings in the back room (which is a larger space with the same tiles but with NO glass) came out so much cleaner, I'm willing to bet the window is the culprit.

I'm wondering what I should use to cover the window to reduce this echo. We don't need to see the window in shot besides a few specific times anyway, so I'm not concerned about literally covering the whole thing up.

I've read up on using blankets (thick, quilted kind) to help do this, but I'd have to order them in at a hefty cost for our budget. What I do have in absolute abundance is cardboard and bubble wrap.

How effective would this be in covering up the echo?

EDIT: We're going to be using the Audix SCX1/HC which is a hypercardioid with quite a directional polar pattern. We're not getting any noise from the back room at all, so we're going to try adjusting the microphone position whenever possible to face towards the back of the shop as the back of the microphone won't pick up anything reflecting back off the windows.

We're also going to construct a 7ft by 10ft "shield" made of sliced and squeezed cardboard with upholstery wadding in the back.

If anybody thinks this is the right idea or has any other suggestions, please let me know.

Answer 1

If it's just dialog that you are recording then rent a couple lav mics if you can then make sure the audio coming off them is nice and usable. The problem with a hypercardioid mic in a reflective room like that is there are always going to be significant secondary reflections off of those hard surfaces. Because a lav is so close to the source those reflections are going to be greatly reduced. Alternatively you could try and hide your mic as close to the source as you can. Unfortunately this will limit your speed and flexibility when setting up your shots.

Cardboard is going to absorb a bit of the mid and high frequency reflections but isn't going to help with the massive weight of the glass and lower frequency sound that reflects back. By lower frequency I'm guessing everything below about 900 Hz is going to wind up as a nice booming echo in your Audix.

Answer 2

Just putting cardboard over the windows will improve things dramatically. A cardboard room is already quite dead. If you have a lot of cardboard, you can concertina it by putting some scores in it with a box cutter and scrunching it so that the surface you are applying to the glass is rippled rather than flat.