Portable VO booths

[Tom Prigge]

Bill,

This is the clearest explanation I’ve ever seen, and one that folks more versed in video than audio can understand. Which is more important–absorption or dispersion of sound waves?

[Ty Ford]

Hi Tom,

It’s a balance of both. I explain sound in a room as similar to a pool table. Toss a ball on a pool table and it hits the cushions until it runs out of energy. In a room the pool table is three dimensional.

Sound deadening is used to keep outside sounds from getting in. That’s normally a D-I-D (density-isolatio-density) sandwich of walls and a space that isolates the walls from each other so they don’t conduct sound. That’s something completely different than treating the insides of the space.

Foam absorbs. Diffusion breaks up the waveforms and scatters them. Inside the space, you typically need a balance of absorption and diffusion to get it right. Hard parallel surfaces are your enemy, e.g. ceiling/floor, wall/wall. Once you tune into that, you can walk into a room, clap your hands and hear the problems and see and hear the areas that need treatment.

See the record albums on in the corner? That shelf systems covers my entire wall; 13 feet by 8 feet tall. Those irregular edges of all the LPs creates a giant diffuser. Books on shelves can do the same thing.

The long horizontal panel is two 2′ x 4′ sheets of 4″ thick acoustic foam squeezed slightly (so they stay there) into 1″ x 4″ boards I attached to the wall with simple L brackets.

Wall to wall covered by a carpet on the floor.

Some (but not all) of the “acoustical” ceiling tiles are are covered in 1″ thick foam to reduce ceiling bounce.

The frame on the left with the foam on it is a stood up base for a slatted platform bed.

The couch also helps.

The carpet on the table helps.

The grey muslin curtain was added when I began to shoot video in this space and needed a more neutral background. It also impacts the sonic signature of the space.

You don’t have to go all scientific once you get the idea. I also use CD storage towers on a chest along the back wall to breakup the soundwaves. You can sort of see them behind the Neumann mic and JBL monitor in the top shot.

The visual for that is imagining what happens when you drop a stone in a pond. It sends out a circular ripple. You want to break that up so it doesn’t hit a flat surface and bounce back to you in tact. Worst possible case…a racquetball court. Still bad…most bathrooms. Usually funky…a stairwell. All bad due to hard parallel surfaces.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford’s Blog

[Bill Davis]

[Tom Prigge] “Which is more important–absorption or dispersion of sound waves?”

Tom.

Which is more important to lighting? Blocking light or reflecting light?

The correct answer is, of course, yes.

In situation A it might well be more important to block it. In situation B, it might be equally critical to diffuse it. Or add more. Or color the light. Or move it. Or move the subject.

If I’m setting a backlight on a bald subject, I might need to fly a flag (absorb the light) to keep down an unwanted shiny spot on their head.

When that’s done, I might notice that the light is creating too defined a shadow under his or her eye sockets, and so I might need to soften that shadow by using diffusion (dispersing the light waves over a larger surface.

The big issue is that with lighting you at least can SEE the difference as you work once you’re trained to look for the results.

Sound is much more subtle. You can’t “see” that high frequencies might be missing or too pronounced. You simply have to learn to LISTEN – and that is usually very difficult for most people. Our brains are very sophisticated about decoding meaning from live sound in the natural world. Microphones don’t have brains and so you have to listen with INTENT if you want to be aware of things that you brain might be filtering out in the field..

This means you must train yourself to understand what good audio should sound like.

Just like we learn to light in layers (key, fill, backlight, ambience, etc.) you have to learn to LISTEN in layers. Primary signal, ambience, room tone, distractions like RF or distant traffic, etc.

It’s only when you learn to be aware of what you’re hearing, that you can bring a tool or technique to bear to try to fix or diminish it.

Welcome to audio!

“Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions.”-Justice O’Connor