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Read along as ASC founder, president and TubeTrap inventor, Art Noxon, PE shares his experience with us this week!

Sound Fusion in Small Rooms

What is the size of a room? Acoustically there are large rooms and small rooms. Large rooms are like a gymnasium and small rooms are like a classroom. In large rooms most of the reflections arrive outside the echo detection threshold, 50 ms or 1/20 sec. In small rooms most of the reflections arrive well inside the echo detection threshold, inside the sound fusion time period, 1/30 second.

For the most part, we live and work inside of acoustically small rooms. This means what we call “indoor sound” is mostly a direct sound followed by 25 or so early reflections of that same sound, which fuse into the direct sound, making it seem louder and giving it some coloration. These early reflections bounce off the surfaces of the small room, surfaces which you have just decorated. Oh oh….What if your decorations make some of these reflections sonically weird. Does that weirdness appear in our perception of the direct sound? By all means available, yes. And so now you can begin to see the connection between the materials and surfaces you use inside a room and how sounds made in the room…. sound.

Now that we know what we are going to talk about, we can begin to talk about it. Let’s explore room acoustics for a little while. Remember, the sound of my voice is a sound fusion of the direct signal that goes from me to you plus some 100 early sound fusing reflections. Since each of you is sitting in a different location, the direct and the set of early reflections are different for each of you. As I move around, the set of signals each of you get change. Your mind averages out all the different variations being delivered into one basic sound. Like we do visually. My face changes a lot when I speak. If you freeze frame it, I would look pretty stupid most of the time but let it just run freely and well, I’m just me, and not any of those stupid looking freeze frame versions of me.

I’m going to speak to you while changing positions in the room and listen to how the sound of my voice changes even though I’m doing my very best to keep speaking the same. As I back up to a wall, my voice seems to become more bass sounding. If I go to the corner, even more. If I talk to you over a desk, I add a single strong early reflection that follows the direct signal by only a few milliseconds and my voice get particularly loud compared to no desk. As I move around the direct + early reflection sound fusion package changes. If I stood still and talked while you moved around the room, the same effect will take place. I’ll stay here and I need some volunteers, one for each corner and a couple against each wall. Walk slowly and keep quiet and listen carefully.

Listening to the Sound of Sound

Speaking of listening carefully, imagine someone who is intently listening. What do they look like? Not as an individual but their posture. What are they doing while listening intently. They are not dancing nor are they looking around for the sound. They are pretty still or slightly swaying. They are staring up or down or ahead but looking at nothing. Often they will touch or hold their face. They pretty much look like they are in a trance. What they are doing is trying to eliminate other sensory inputs which are usually overpowering our ability to listen. We are always hearing sound but to listen deeply, we have to shut down inputs from all other senses, in particular, the visual sense.

I had an interesting experience when I was a lot younger and in grad school for the first time, finishing up my thesis in acoustics. I woke up in the middle of the night and rubbed my eyes. Despite washing my hands the glue was still on my hands and my eyes caught on fire. Went to ER and after getting pain medicine and bandaged up the doc said that I might or might not see after the bandages come off in 2 weeks. I had put a lot of chemicals in my eye and could have scarred the lens. Only after the bandages come off would we know….prepare for the worst. With that, I was sent home.

I was led around for a while and fumbled around by myself but trying to memorize where everything was located seemed impossible. But within hours something new was happening. I began hearing where I was. I could hear when I was walking towards a wall. I could hear where the doorway was located. I could hear curbs, trees, fences and lots of things. The world was rapidly becoming clear again in a dark and murky sort of way. I had lost my visual sight but was connecting with my hearing sight. Little did I know at that time, I was peeking into what would become the body of my life’s work. After 2 weeks, the bandages came off and with my sight restored I quickly forgot all about how to live in the dark. It took another 15 years before I realized I had become completely involved in helping people see sound and I’ve been lucky enough to have been able to continue doing so for the last 25 years, now. Let’s return to the present, the sound of the space we are in.

Continue reading Art’s article