Sound Check Room Sounds - Avoid the Node
posted by April 6 at 11:31 AMon
This is usually a Thursday post, next week it will back on Thursday.
** Gary and Jon will be monitoring this, so if you have any questions, ask away.
When dealing with room sounds, Trigonometry is involved. Be not afraid. Proceed, crank, and yield the rock that is within you.
They speak of modes. Room modes are the result of standing waves and sound being reflected back off the walls and interfering with the original travelling wave. At certain frequencies, there will be some points in the room where the waveforms will add to produce a node or loud spot, and others where cancellation occurs to produce an antinode.
The dimensions of any room are going to accentuate or cut out certain frequencies. Better sounding rooms have fewer modes. Every room has itís decay time too.
When dealing with room sounds, there is reflection, absorption, and diffusion.
Reflection is what happens when the sound bounces off the wall. Parallel walls are bad. In square rooms, the soundwaves bounce back and forth and make your recording sound like shit. You want unparallel walls and surfaces. Splaying the walls is what itís called when you make them unparallel.
Absorption helps deaden the sound and keep your frequencies from going crazy. Studio foam and compressed fiberglass are other things that absorb. You can use bass traps for low end.
Diffusion is a brick wall. Diffusion disperses or scatters the sound and makes for even sound distribution. Anything with hard uneven surfaces.
Living rooms can be great places to record. Windows are good, they give sound and frequencies a place to escape. But at home, in the living room, you have to deal with neighbors. Also, there are ambulances going by or jets flying over that could mess with your recording. So people go into the basement, with square walls and no windows - not an acoustical friendly place to be.
Another problem at home is that the dry wall or plaster in your walls vibrates and essentially becomes a drum head. The frequency of that vibration is going to cancel out whatever else is at that frequency. Say your wall is vibrating at 100 Hz. Well that cancels out your bass and kick drum.
In the studio, we have 4 layers of dry wall and all this compressed fiberglass that help. Itís just a matter of working with a room and knowing where the weird boosts and dips are.
Auralex and RPG Diffusion make good sound design kits.
Jonathan Plum from London Bridge says:
You can try every mic or compression technique in the book, but you can't mask or enhance a bad sounding room.
Itís always about experimenting. I often, by accident, find a great room sound out of a mic I set up for the singer to sing scratch tracks. This happens all the time.
In smaller rooms, you can place a uni direction mic close to the source yet pointing away to maximize the size and length of the room. Fast compression on a room mic can strongly change the apparent size of a room. With a fast attack and fast release you can virtually eliminate the source sound and isolate the slap back and ambiance of the room. Adding too much compression will usually lead to an unnatural washy sound.
Ultra bright room mic's tend to get too washy. I try to find a warm sounding mic like the Neumann U87 or Royer ribbon. An sm7 is also a good room mic.
Sometimes it's hard not get rid of a room sound. Some spaces can be so live that you have to fight to get a close sound. Oops. Getting off subject here.
I've had great success recording in my friends kitchen. He has a large open area with hard wood floors and a slanted ceiling. Parallel walls just make the sound echo back and forth.
Put a couch in there, a mattresses on the wall. Tip over a table on an angle.
Best places to record are large open spaces with varied surfaces (ie brick, wood, fabric).
A room sound is essential if you want your recording to sound as if there was a musical performance that took place in a specific time and space. Room sounds give the listener a reference to where the performance took place. The listener can get inside the recording not just in front of it.